US20140053064A1 - Predicting the usage of document resources - Google Patents

Abstract

Browser systems and methods of loading/rendering a webpage include preprocessing the web document (HTML page) using speculation/prediction techniques to identify the resources that are likely to be required from an incomplete set of information, and requesting/pre-fetching the resources that are determined to have a high probability of being required for proper rending of the web document. The speculation/prediction techniques may include the use of heuristics to improve the efficiency and speed of document loads and network communications.

Description

CROSS REFERENCE TO RELATED PATENT APPLICATIONS
• This application claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 61/684,593 entitled “Predicting the Usage of Document Resources” filed Aug. 17, 2012 and U.S. Provisional Patent Application Ser. No. 61/684,002 entitled “Predicting the Usage of Document Resources” filed Aug. 16, 2012, the entire contents of both of which are hereby incorporated by reference.
• This application is also related to U.S. patent application Ser. No. ______ entitled “Pre-Processing of Scripts in Web Browsers” filed concurrently with this application.
• This application is also related to U.S. patent application Ser. No. ______ entitled “Speculative Resource Prefetching via Sandboxed Execution” filed concurrently with this application.
FIELD OF THE INVENTION
• The present invention relates to methods, systems, and devices for rendering HTML documents in a web browser, and more particularly to methods of parallelizing web browser operations.
BACKGROUND
• Wireless communication technologies and mobile electronic devices (e.g., cellular phones, tablets, laptops, etc.) have grown in popularity and use over the past several years. To keep pace with increased consumer demands, mobile electronic devices have become more feature rich, and now commonly include multiple processors, system-on-chips (SoCs), and other elements that allow mobile device users to execute complex and power intensive software applications (e.g., web browsers, video streaming applications, etc.) on their mobile devices. Due to these and other improvements, smartphones and tablet computers have grown in popularity, and are replacing laptops and desktop machines as the platform of choice for many users.
• Mobile device users can now accomplish many their daily tasks with ease and convenience by accessing the Internet via browser applications on their mobile device. As mobile devices continue to grow in popularity, web browsers that are able to better utilize the multiprocessing capabilities of the modern mobile devices will be desirable to consumers.
SUMMARY
• The various aspects include methods of processing a webpage, which may include scanning an HTML document by a first process to discover external resources referenced in the HTML document, the first process executing in a processor of a computing device concurrent with an HTML parser process, invoking by the first process a downloading of a resource document for a discovered external resource, the downloading being performed while the first process continues scanning the HTML document, scanning the downloaded resource document by a second process to discover additional external resources, the second process scanning the downloaded resource document while the first process continues scanning the HTML document, identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document, receiving by the second process information pertaining to the attributes identified by the first process, determining whether to initiate downloading of discovered additional resources by the second process based on the received information, and rendering the HTML document on an electronic display of the computing device using the downloaded resources.
• In an aspect, scanning an HTML document by a first process may include scanning the HTML document by an HTML document scanner process. In a further aspect, scanning the downloaded resource document by a second process may include scanning the downloaded resource document by a cascading style sheet document scanner process. In a further aspect, determining whether to initiate downloading of discovered additional resources by the second process based on the received information may include speculating regarding external resources required for rendering the HTML document on the electronic display of the computing device.
• In a further aspect, scanning the downloaded resource document to discover additional external resources may include scanning a style sheet document by the second process to discover additional external resources. In a further aspect, identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document may include identifying by the first process HTML id, class, and style attributes associated with HTML elements included the HTML document, and receiving information pertaining to the attributes identified by the first process may include receiving by the second process information pertaining to the identified HTML id, class, and style attributes associated with HTML elements included the HTML document.
• In a further aspect, determining by the second process whether to download discovered additional resources based on the received information may include determining whether every identified HTML id, class, and style attribute associated with a style rule has already been encountered by the HTML document scanner, immediately requesting resources referenced by the style rule in response to determining that every identified HTML id, class, and style attribute associated with the style rule has already been encountered by the HTML document scanner, and storing the style rule in memory in response to determining that not every identified HTML id, class, and style attribute associated with the style rule has been encountered by the HTML document scanner.
• In a further aspect, the method may include generating a notification by the first process when scanning of the HTML document is complete, and receiving the notification by the second process. In a further aspect, the method may include retrieving the stored style rule from memory by the second process in response to the second process receiving the notification, determining whether every HTML id, class, and style attribute has already been encountered by the first process, and requesting resources referenced by the retrieved style rule in response to determining that every HTML id, class, and style attribute has already been encountered by the first process.
• Further aspects include a computing device that includes means for scanning an HTML document by a first process to discover external resources referenced in the HTML document, the first process executing concurrent with an HTML parser process, means for invoking by the first process a downloading of a resource document for a discovered external resource, the downloading being performed while the first process continues scanning the HTML document, means for scanning the downloaded resource document by a second process to discover additional external resources, the second process scanning the downloaded resource document while the first process continues scanning the HTML document, means for identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document, means for receiving by the second process information pertaining to the attributes identified by the first process, means for determining whether to initiate downloading of discovered additional resources by the second process based on the received information, and means for rendering the HTML document on an electronic display of the computing device using the downloaded resources.
• In an aspect, means for scanning an HTML document by a first process may include means for scanning the HTML document by an HTML document scanner process, and means for scanning the downloaded resource document by a second process may include means for scanning the downloaded resource document by a cascading style sheet document scanner process. In a further aspect, means for determining whether to initiate downloading of discovered additional resources by the second process based on the received information may include means for speculating regarding external resources required for rendering the HTML document on the electronic display.
• In a further aspect, means for scanning the downloaded resource document to discover additional external resources may include means for scanning a style sheet document by the second process to discover additional external resources. In a further aspect, means for identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document may include means for identifying by the first process HTML id, class, and style attributes associated with HTML elements included the HTML document, and means for receiving information pertaining to the attributes identified by the first process may include means for receiving by the second process information pertaining to the identified HTML id, class, and style attributes associated with HTML elements included the HTML document.
• In a further aspect, means for determining by the second process whether to download discovered additional resources based on the received information may include means for determining whether every identified HTML id, class, and style attribute associated with a style rule has already been encountered by the HTML document scanner, means for immediately requesting resources referenced by the style rule in response to determining that every identified HTML id, class, and style attribute associated with the style rule has already been encountered by the HTML document scanner, and means for storing the style rule in memory in response to determining that not every identified HTML id, class, and style attribute associated with the style rule has been encountered by the HTML document scanner.
• In a further aspect, the computing device may include means for generating a notification by the first process when scanning of the HTML document is complete, and means for receiving the notification by the second process. In a further aspect, the computing device may include means for retrieving the stored style rule from memory by the second process in response to the second process receiving the notification, means for determining whether every HTML id, class, and style attribute has already been encountered by the first process, and means for requesting resources referenced by the retrieved style rule in response to determining that every HTML id, class, and style attribute has already been encountered by the first process.
• Further aspects include a computing device having a processor configured with processor-executable instructions to perform operations that may include scanning an HTML document by a first process to discover external resources referenced in the HTML document, the first process executing concurrent with an HTML parser process, invoking by the first process a downloading of a resource document for a discovered external resource, the downloading being performed while the first process continues scanning the HTML document, scanning the downloaded resource document by a second process to discover additional external resources, the second process scanning the downloaded resource document while the first process continues scanning the HTML document, identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document, receiving by the second process information pertaining to the attributes identified by the first process, determining whether to initiate downloading of discovered additional resources by the second process based on the received information, and rendering the HTML document on an electronic display of the computing device using the downloaded resources.
• In an aspect, the processor may be configured with processor-executable instructions such that scanning an HTML document by a first process may include scanning the HTML document by an HTML document scanner process, and scanning the downloaded resource document by a second process may include scanning the downloaded resource document by a cascading style sheet document scanner process.
• In a further aspect, the processor may be configured with processor-executable instructions such that determining whether to initiate downloading of discovered additional resources by the second process based on the received information may include speculating regarding external resources required for rendering the HTML document on the electronic display of the computing device. In a further aspect, the processor may be configured with processor-executable instructions such that scanning the downloaded resource document to discover additional external resources may include scanning a style sheet document by the second process to discover additional external resources.
• In a further aspect, the processor may be configured with processor-executable instructions such that identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document may include identifying by the first process HTML id, class, and style attributes associated with HTML elements included the HTML document, and receiving information pertaining to the attributes identified by the first process may include receiving by the second process information pertaining to the identified HTML id, class, and style attributes associated with HTML elements included the HTML document.
• In a further aspect, the processor may be configured with processor-executable instructions such that determining by the second process whether to download discovered additional resources based on the received information may include determining whether every identified HTML id, class, and style attribute associated with a style rule has already been encountered by the HTML document scanner, immediately requesting resources referenced by the style rule in response to determining that every identified HTML id, class, and style attribute associated with the style rule has already been encountered by the HTML document scanner, and storing the style rule in memory in response to determining that not every identified HTML id, class, and style attribute associated with the style rule has been encountered by the HTML document scanner. In a further aspect, the processor may be configured with processor-executable instructions to perform operations further including generating a notification by the first process when scanning of the HTML document may be complete, and receiving the notification by the second process.
• In a further aspect, the processor may be configured with processor-executable instructions to perform operations further including retrieving the stored style rule from memory by the second process in response to the second process receiving the notification, determining whether every HTML id, class, and style attribute has already been encountered by the first process, and requesting resources referenced by the retrieved style rule in response to determining that every HTML id, class, and style attribute has already been encountered by the first process.
• Further aspects include a non-transitory computer readable storage medium having stored thereon processor-executable software instructions configured to cause a processor to perform operations for processing a webpage, the operations including scanning an HTML document by a first process to discover external resources referenced in the HTML document, the first process executing concurrent with an HTML parser process, invoking by the first process a downloading of a resource document for a discovered external resource, the downloading being performed while the first process continues scanning the HTML document, scanning the downloaded resource document by a second process to discover additional external resources, the second process scanning the downloaded resource document while the first process continues scanning the HTML document, identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document, receiving by the second process information pertaining to the attributes identified by the first process, determining whether to initiate downloading of discovered additional resources by the second process based on the received information, and rendering the HTML document on an electronic display of the computing device using the downloaded resources.
• In an aspect, the stored processor-executable software instructions are configured to cause a processor to perform operations such that scanning an HTML document by a first process may include scanning the HTML document by an HTML document scanner process, and scanning the downloaded resource document by a second process may include scanning the downloaded resource document by a cascading style sheet document scanner process.
• In a further aspect, the stored processor-executable software instructions are configured to cause a processor to perform operations such that determining whether to initiate downloading of discovered additional resources by the second process based on the received information may include speculating regarding external resources required for rendering the HTML document on the electronic display of the computing device.
• In a further aspect, the stored processor-executable software instructions are configured to cause a processor to perform operations such that scanning the downloaded resource document to discover additional external resources may include scanning a style sheet document by the second process to discover additional external resources.
• In a further aspect, the stored processor-executable software instructions are configured to cause a processor to perform operations such that identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document may include identifying by the first process HTML id, class, and style attributes associated with HTML elements included the HTML document, and receiving information pertaining to the attributes identified by the first process may include receiving by the second process information pertaining to the identified HTML id, class, and style attributes associated with HTML elements included the HTML document.
• In a further aspect, the stored processor-executable software instructions are configured to cause a processor to perform operations such that determining by the second process whether to download discovered additional resources based on the received information may include determining whether every identified HTML id, class, and style attribute associated with a style rule has already been encountered by the HTML document scanner, immediately requesting resources referenced by the style rule in response to determining that every identified HTML id, class, and style attribute associated with the style rule has already been encountered by the HTML document scanner, and storing the style rule in memory in response to determining that not every identified HTML id, class, and style attribute associated with the style rule has been encountered by the HTML document scanner.
• In a further aspect, the stored processor-executable software instructions are configured to cause a processor to perform operations including generating a notification by the first process when scanning of the HTML document is complete, and receiving the notification by the second process. In a further aspect, the stored processor-executable software instructions are configured to cause a processor to perform operations including retrieving the stored style rule from memory by the second process in response to the second process receiving the notification, determining whether every HTML id, class, and style attribute has already been encountered by the first process, and requesting resources referenced by the retrieved style rule in response to determining that every HTML id, class, and style attribute has already been encountered by the first process.
BRIEF DESCRIPTION OF THE DRAWINGS
• The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate exemplary aspects of the invention. Together with the general description given above and the detailed description given below, the drawings serve to explain features of the invention not to limit the disclosed aspects.
• FIG. 1 is a component block diagram illustrating an example system-on-chip (SOC) architecture that may be used in computing devices implementing the various aspects.
• FIG. 2 is a function block diagram illustrating an example multicore processor architecture that may be used to implement the various aspects.
• FIG. 3A is a process flow diagram illustrating an aspect browser method for rending an HTML document.
• FIG. 3B is a function and process flow diagram illustrating example logical components, information flows, operations, and transformations in an aspect browser system.
• FIG. 4 is a function block diagram illustrating example logical components, functional components, information flows, and subsystems in an aspect browser system.
• FIG. 5 is a function block diagram illustrating an aspect browser system that implements a parallel browser infrastructure in accordance with an aspect method.
• FIG. 6 is a process flow diagram illustrating an aspect browser method of processing an HTML document to discover and pre-fetch resources in advance of the page loading/rendering operations.
• FIG. 7A is a process flow diagram illustrating an aspect browser method of using speculation techniques and heuristics to predict the usage of document resources.
• FIG. 7B is a process flow diagram illustrating an aspect browser method of speculatively pre-fetching resources in parallel.
• FIG. 7C is a process flow diagram illustrating an aspect browser method of preprocessing scripts in parallel.
• FIG. 8 is a process flow diagram illustrating an aspect browser method of processing pre-fetched resources.
• FIG. 9 is a function block diagram illustrating example functional components in CSS engine suitable for use with the various aspects.
• FIG. 10 is a process flow diagram illustrating an aspect styling method for performing rule matching and cascading operations on several nodes in parallel.
• FIG. 11A is an illustration of an example document object model (DOM) tree suitable for use in various aspects.
• FIG. 11B is an illustration of a task directed acyclic graph (DAG) corresponding to the DOM tree illustrated inFIG. 11A.
• FIG. 12 is a component block diagram of an example mobile device suitable for use with the various aspects.
• FIG. 13 is a component block diagram of an example server suitable for use with various aspects.
• FIG. 14 is a component block diagram of a lap top computer suitable for implementing the various aspects.
DETAILED DESCRIPTION
• The various aspects will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. References made to particular examples and implementations are for illustrative purposes and are not intended to limit the scope of the invention or the claims.
• The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations.
• The terms “mobile device,” and “computing device” are used interchangeably herein to refer to any one or all of cellular telephones, smartphones, personal or mobile multi-media players, personal data assistants (PDA's), laptop computers, tablet computers, smartbooks, palm-top computers, wireless electronic mail receivers, multimedia Internet enabled cellular telephones, wireless gaming controllers, and similar personal electronic devices which include a programmable processor and a memory. While the various aspects are particularly useful in mobile devices, such as cellular telephones, which may have limited processing power, the aspects are generally useful in any computing device that executes scripts and/or applications written in dynamic, scripting and/or markup languages.
• Web browsers are complex software applications that implement multiple standards, need to support legacy behavior, and are highly dynamic and interactive. Web browser designers generally aim to achieve an optimal mix of fast response times for page loads (even in the presence of long network latencies), high performance (e.g., to enable interactivity for web applications), and high user interface responsiveness to provide a good user experience.
• The various aspects provide web browsers, browser methods, and browser systems configured to achieve fast response times, high performance, and high user interface responsiveness via the use of heuristics, speculation, resource pre-fetching, and/or techniques that exploit the concurrency/parallelism enabled by modern multiprocessor mobile device architectures.
• Modern web documents (e.g., HTML pages, HTML documents, etc.) may reference a large number of external resources, and each referenced external resource may include references to other external resources. For example, HTML documents typically include references to images, audio, Cascading Style Sheets (CSS), and JavaScript®, and the referenced resources (e.g., CSS, audio, JavaScript®) may further include references to additional external resources (e.g., images, audio, etc.). Typically, not all of the referenced external resources are required (or even used) to properly render the webpage on an electronic display of a mobile device.
• Loading and rendering a webpage on a mobile device typically requires that a web browser parse an HTML document to identify external resources (images, audio, CSS, etc.) referenced in the document. Conventional browser solutions may request each of the identified external resources from one or more network servers, and suspend further processing of the webpage until all of the external resources are received from the network servers. Due to the large number of resources referenced in modern web documents (and the suspension of browser operations while the external resources are downloaded), a mobile device may experience slow document load speeds and high latency times when downloading resources discovered in HTML and CSS code/content.
• Conventional web browser solutions may attempt to speed up the page/document load speeds by caching portions of web pages in memory to reduce the amount of information that must be downloaded the next time the page is accessed. However, using these conventional solutions, a web browser cannot identify the external resources that are required to render a web page for the first time without first analyzing the entire document (i.e., webpage), requesting and receiving most (if not all) of the resources referenced in the document and subdocuments, and analyzing the received resources. Thus, using conventional solutions, the precise set of resources required by the document cannot be determined until after the entire document has been fully analyzed.
• A web browser may be configured to scan a web document to discover and download all of the referenced external resources in advance. However, due to the large number of resources that may be referenced, blindly downloading all of the referenced resources may be more detrimental to document load speeds and latency times than conventional web browser solutions in which the external references are requested as they are discovered. For example, it is common practice among websites to reference many more resources than are actually needed for any given document by, for example, using a site-wide common style file. Downloading all of these referenced external resources may further reduce document load speeds, consume excess bandwidth, and increase latency times.
• The various aspects include browser systems and methods of loading/rendering a webpage by preprocessing the web document (HTML page) using speculation/prediction techniques to identify the resources that are likely to be required from an incomplete set of information, and requesting/pre-fetching the resources that are determined to have a high probability of being required for proper rending of the web document. Pre-fetching of these resources may enable the web browser (and thus the mobile device) to better utilize the available bandwidth, overlap the transfer latencies, and improve document load times.
• Various aspects may speculatively download resources based on heuristics to improve the efficiency and speed of document loads and network communications. Various aspects may compute, generate, select, and/or apply one or more heuristics to maximize the number of true positives and true negative while minimizing the number of false positive and false negative download decisions. Various aspects may maximize the number of true positives and true negatives by identifying the resources that are likely to be required using information obtained during an initial scan of a web document.
• Various aspects may speculatively download resources based on a “CSS rule” heuristic that is highly effective for discovering required resources, and for which incorrect speculations do not have a significant negative impact on the web browser (and thus the mobile device).
• As used in this application, the terms “component,” “module,” “system,” “subsystem,” “engine,” “manager” and the like are intended to include a computer-related entity, such as, but not limited to, hardware, firmware, a combination of hardware and software, software, or software in execution, which are configured to perform particular operations or functions. For example, a component may be, but is not limited to, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, a procedure, a software application, and/or a computer. By way of illustration, both an application running on a computing device and the computing device may be referred to as a component. One or more components may reside within a process and/or thread of execution and a component may be localized on one processor or core and/or distributed between two or more processors or cores. In addition, these components may execute from various non-transitory computer readable media having various instructions and/or data structures stored thereon. Components may communicate by way of local and/or remote processes, function or procedure calls, electronic signals, data packets, memory read/writes, and other known computer, processor, and/or process related communication methodologies.
• The term “system on chip” (SOC) is used herein to refer to a single integrated circuit (IC) chip that contains multiple resources and/or processors integrated on a single substrate. A single SOC may contain circuitry for digital, analog, mixed-signal, and radio-frequency functions. A single SOC may also include any number of general purpose and/or specialized processors (digital signal processors, modem processors, video processors, etc.), memory blocks (e.g., ROM, RAM, Flash, etc.), and hardware resources (e.g., timers, voltage regulators, oscillators, etc.). SOCs may also include software for controlling the integrated hardware resources and processors, as well as for controlling peripheral devices.
• The term “multicore processor” is used herein to refer to a single integrated circuit (IC) chip or chip package that contains two or more independent processing cores (e.g., CPU cores) configured to read and execute program instructions. A SOC may include multiple multicore processors, and each processor in an SOC may be referred to as a core. The term “multiprocessor” is used herein to refer to a system or device that includes two or more processing units configured to read and execute program instructions.
• The term “application programming interface” and its acronym “API” are used generically in this application to refer to any software interface that may be used by a first software component to communicate with a second software component. An API may include specifications for routines, procedures, functions, methods, data structures, object classes, and variables. An API may also include facilities for mapping the API to features (syntactic or semantic) of another high-level programming language. Such facilities and/or mappings may themselves be APIs, and are known as “language bindings” or “bindings.”
• The term “markup language” is used generically in this application to refer to any programming language and/or system for annotating text so that a processor may syntactically distinguish the annotations from the text. Examples of markup languages include Scribe, Standard Generalized Markup Language (SGML), Hyper-Text Markup Language (HTML), Extensible Markup Language (XML), and Extensible Hyper-Text Markup Language (XHTML).
• The terms “dynamic language” and “scripting language” are used generically and interchangeably in this application to refer to any dynamic language, scripting language, or to any language used to write programs (herein as “scripts”) that are interpreted and/or compiled at runtime. These terms may also refer to any language that runs on a managed runtime and is dynamically compiled. Thus, usage of the terms “dynamic language” and “scripting language” in the description of the various aspects should not be construed as limiting the claims to languages that are interpreted from source code or bytecode, or to those that execute along with programs that are traditionally compiled into native machine code. Examples of dynamic and scripting languages within the scope of this application include, for example, JavaScript®, Perl, Python, and Ruby, as well as other similar languages that may be developed in the future.
• The terms “style sheet language” and “style language” are used generically in this application to refer to any computer language that expresses the presentation of structured documents so that the presentation style of the document may be separated from the content of the document. An example of a style sheet language is Cascading Style Sheets (CSS), which is typically used for describing the presentation semantics of a document written in a markup language.
• For ease of reference, throughout this application, HTML is used as an exemplary markup language, CSS is used as an exemplary style sheet language, and JavaScript® is used as an exemplary dynamic scripting language. However, it should be noted that the use of HTML, CSS, and JavaScript® in this application is only for purposes of illustration, and should not be construed to limit the scope of the claims to a particular language unless expressly recited by the claims.
• HTML is a markup language that implements the ISO/IEC 15445 standard. HTML may be characterized as a set of markup tags (e.g., annotations) used to describe web pages so that they can be displayed by a software application, such as a web browser. HTML allows for the creation of structured documents by denoting structural semantics for text, such as headings, paragraphs, lists, links, quotes, and other items.
• JavaScript® is a dynamic, weakly typed, object-oriented scripting language that implements the ECMAScript language standard (standardized by ECMA International in the ECMA-262 specification) and/or the ISO/IEC 16262 standard. JavaScript® enables programmatic access to computational objects within a host environment, such as web browsers executing on a mobile device processor.
• Cascading Style Sheets (CSS) is a style language used to describe the look and formatting of web sites, and is intended to be used to separate the presentation of a document from its content. Each style sheet may include an ordered collection of rules with the following format: selector {property₁: value; . . . property_n: value;}. As an example, the following CSS code tells the browser to render all <cite> elements whose direct ancestor is a <p> element using a white foreground over a red background: p>cite {color: white; background-color: red;}. It is not uncommon for websites to include tens of thousand of such rules.
• HTML may embed and/or include links to JavaScript® code capable of affecting the behavior and/or presentation of the containing HTML page. The embedded/linked JavaScript® code may also generate additional HTML code, which can be inserted into the containing HTML page (i.e., the HTML code in which the JavaScript® is embedded).
• JavaScript® may be used to embed functions into HTML code so that the functions interact with, and manipulate, the document object model (DOM) of the HTML page. DOM is a language-independent convention for representing and interacting with objects in HTML, and allows the JavaScript® code to have access to, and manipulate, the containing HTML page. A DOM tree is typically generated as part of rendering a web page to identify the components, relative structures, relationships, and behaviors of the respective components that define the page.
• HTML can include (e.g., embed and/or link to) CSS code. CSS code may be specified as separate files, which may be stored on remote servers. Conventional CSS processing engines (e.g., WebKit or Firefox) parse CSS sequentially in the main browser thread and do not support a high degree of parallelism or concurrency. For example, when CSS code is embedded into the HTML document, an HTML parser cannot parse remaining portions of an HTML document until the CSS engine has parsed the style elements in the HTML document's header. When an HTML document includes links to several CSS files, conventional CSS processing engines will parse all the linked CSS files sequentially. For these and other reasons, conventional CSS processing engines may cause severe slowdowns, especially in the case of large CSS files (which is common).
• In recent years, mobile electronic devices (e.g., cellular phones, tablets, laptops, etc.) have become more feature rich, and now commonly include multiple processors, system-on-chips (SoCs), multiple memories, and other components that allow mobile device users to execute complex and power intensive software applications (e.g., web browsers, video streaming applications, etc.) on their mobile devices. Due to these and other improvements, smartphones and tablet computers have grown in popularity, and are replacing laptops and desktop machines as the platform of choice for many users. Mobile device users can now accomplish many their daily tasks with ease and convenience by accessing the Internet via a web browser of their mobile device. However, existing web browsers and web browser solutions do not support a high degree of parallelism or concurrency, and thus fail to fully utilize the multiprocessing capabilities of the mobile devices.
• The various aspect methods, systems, and browsers take advantage of the parallelism available in modern mobile devices to improve the efficiency and speed of page and document loads, web applications, and network communications.
• Exploiting concurrency in web browsers is a relatively new approach. Most existing browsers (e.g., Firefox, the WebKit-based Chrome and Safari browsers, etc.) are fundamentally architected as sequential engines that use event driven models to help with interactivity. Due to the large number of dependencies between mobile device and/or browser subsystems (and because many existing data structures aren't thread safe) existing solutions do not support a high degree of parallelism or concurrency.
• Chrome and the WebKit2 generate separate processes for each browser tab, which provides some isolation between different web sites, but delegates the responsibility of using multiple cores to the operating system. In addition, these processes are heavyweight in terms of both memory and startup overhead. As such, these solutions do not speed up individual page loads or improve the efficiency of network communications, but simply support parallelism with respect to executing multiple instances of the same application. Such tab-level parallelism doesn't address the needs of mobile browsers, where single-tab performance is often inadequate and users don't open many tabs at once.
• The OP and OP2 browsers may generate a new collection of processes per web page (called a “web instance”), and browser components (e.g., networking) may run in different processes. However, these solutions, like all other existing browser solutions, are still inherently sequential. For example, while a network operation may be performed in a separate process as a parse operation, the network process must still wait on a parse process (and vice versa) because each operation is dependent on the other. That is, while OP and OP2 browsers allow for the use of multiple processes or threads, these solutions do not achieve a high degree of parallelism in rendering a webpage because they do not address the serial/sequential nature of browser processing algorithms for downloading, processing, and rendering webpages.
• The various aspects include high-performance web browser and browser solutions that overcome the serial/sequential nature of existing browser processing algorithms, utilize the multi-thread execution and parallel processing capabilities of high-speed processors and multiprocessor mobile device architectures, and exploit parallelism pervasively to improve browser performance, reduce network latency, and improve the user experience for users of mobile devices.
• The various aspects may be implemented on a number of single processor and multiprocessor computer systems, including a system-on-chip (SOC).FIG. 1 illustrates an example system-on-chip (SOC)100 architecture that may be used in computing devices implementing the various aspects. TheSOC100 may include a number of heterogeneous processors, such as a digital signal processor (DSP)102, amodem processor104, agraphics processor106, and anapplication processor108. TheSOC100 may also include one or more coprocessors110 (e.g., vector co-processor) connected to one or more of theheterogeneous processors102,104,106,108. Eachprocessor102,104,106,108,110 may include one or more cores, and each processor/core may perform operations independent of the other processors/cores. For example, theSOC100 may include a processor that executes a first type of operating system (e.g., FreeBSD, LINUX, OS X, etc.) and a processor that executes a second type of operating system (e.g., Microsoft Windows 8).
• TheSOC100 may also include analog circuitry andcustom circuitry114 for managing sensor data, analog-to-digital conversions, wireless data transmissions, and for performing other specialized operations, such as processing encoded audio and video signals for rendering in a web browser. TheSOC100 may further include system components andresources116, such as voltage regulators, oscillators, phase-locked loops, peripheral bridges, data controllers, memory controllers, system controllers, access ports, timers, and other similar components used to support the processors and software clients (e.g., a web browser) running on a computing device.
• The system components andresources116 and/orcustom circuitry114 may include circuitry to interface with peripheral devices, such as cameras, electronic displays, wireless communication devices, external memory chips, etc. Theprocessors102,104,106,108 may be interconnected to one ormore memory elements112, system components andresources116, andcustom circuitry114 via an interconnection/bus module124, which may include an array of reconfigurable logic gates and/or implement a bus architecture (e.g., CoreConnect, AMBA, etc.). Communications may be provided by advanced interconnects, such as high performance networks-on chip (NoCs).
• TheSOC100 may further include an input/output module (not illustrated) for communicating with resources external to the SOC, such as aclock118 and avoltage regulator120. Resources external to the SOC (e.g.,clock118, voltage regulator120) may be shared by two or more of the internal SOC processors/cores (e.g., aDSP102, amodem processor104, agraphics processor106, anapplication processor108, etc.).
• In addition to theSOC100 discussed above, the various aspects may be implemented in a wide variety of computing systems, which may include a single processor, multiple processors, multicore processors, or any combination thereof.
• FIG. 2 illustrates an example multicore processor architecture that may be used to implement the various aspects. Themulticore processor202 may include two or moreindependent processing cores204,206,230,232 in close proximity (e.g., on a single substrate, die, integrated chip, etc.). The proximity of theprocessing cores204,206,230,232 allows memory to operate at a much higher frequency/clock-rate than is possible if the signals have to travel off-chip. Moreover, the proximity of theprocessing cores204,206,230,232 allows for the sharing of on-chip memory and resources (e.g., voltage rail), as well as for more coordinated cooperation between cores.
• Themulticore processor202 may include a multi-level cache that includes Level 1 (L1)caches212,214,238,240 and Level 2 (L2)caches216,226,242. Themulticore processor202 may also include a bus/interconnect interface218, amain memory220, and an input/output module222. TheL2 caches216,226,242 may be larger (and slower) than theL1 caches212,214,238,240, but smaller (and substantially faster) than amain memory220 unit. Eachprocessing core204,206,230,232 may include aprocessing unit208,210,234,236 that has private access to anL1 cache212,214,238,240. Theprocessing cores204,206,230,232 may share access to an L2 cache (e.g., L2 cache242) or may have access to an independent L2 cache (e.g.,L2 cache216,226).
• The L1 and L2 caches may be used to store data frequently accessed by the processing units, whereas themain memory220 may be used to store larger files and data units being accessed by theprocessing cores204,206,230,232. Themulticore processor202 may be configured so that theprocessing cores204,206,230,232 seek data from memory in order, first querying the L1 cache, then L2 cache, and then the main memory if the information is not stored in the caches. If the information is not stored in the caches or themain memory220,multicore processor202 may seek information from an external memory and/or ahard disk memory224.
• Theprocessing cores204,206,230,232 may communicate with each other via the bus/interconnect interface218. Eachprocessing core204,206,230,232 may have exclusive control over some resources and share other resources with the other cores.
• Theprocessing cores204,206,230,232 may be identical to one another, be heterogeneous, and/or implement different specialized functions. Thus, processingcores204,206,230,232 need not be symmetric, either from the operating system perspective (e.g., may execute different operating systems) or from the hardware perspective (e.g., may implement different instruction sets/architectures).
• Multiprocessor hardware designs, such as those discussed above with reference toFIGS. 1 and 2, may include multiple processing cores of different capabilities inside the same package, often on the same piece of silicon. Symmetric multiprocessing hardware includes two or more identical processors connected to a single shared main memory that are controlled by a single operating system. Asymmetric or “loosely-coupled” multiprocessing hardware may include two or more heterogeneous processors/cores that may each be controlled by an independent operating system and connected to one or more shared memories/resources.
• FIG. 3A illustrates anaspect browser method300 of loading and rendering an HTML document. Inblock302, a web browser component may receive a user input requesting the loading of an HTML document located at a particular uniform resource locator (URL). Inblock304, the web browser component may request the HTML document from a web server located at the URL via well known hypertext transfer protocol (HTTP) messages communicated via the Internet. Inblock306, the web browser component may receive the HTML document from a web server located at the URL. Inblock308, the web browser component may parse the received HTML document to identify/discover external resources (images, audio, CSS, etc.) referenced in the HTML file.
• Inblock310, the web browser component may request the identified external resources from network servers where the resources are maintained, which may include the server that provided the HTML document or any other server accessible via the Internet. Inblock312, the web browser component may receive the requested external resources from the network server. Indetermination block314, the web browser component may determine whether any of the received resources reference other external resources.
• When the web browser component determines that the received resources reference other external resources (i.e., determination block314=“Yes”), the web browser may request/receive those other/additional external resources referenced by newly received resources in blocks310-314. These operations may be repeatedly preformed until all referenced external resources have been downloaded.
• When the web browser determines that the received resources do not reference any additional external resources (i.e., determination block314=“No”), inblock316, the web browser may analyze the received external resources to determine the resources that are required to properly render the webpage. Inblock318, the web browser may render the webpage using the required download resources.
• FIG. 3B illustrates example logical components, information flows, operations, and transformations in anaspect browser system350. Thebrowser system350 may be a software application/module configured to cause a processor to perform various operations for retrieving information and/or resources from the Internet and rendering webpages on an electronic display of a computing device (e.g., a mobile device).
• Thebrowser system350 may include ascripting component362 configured to interact with the web page at various stages and/or during various operations (e.g., during and after the page load operations, etc.) to provide interactivity withexternal modules380. Theexternal modules380 may include user I/O modules (e.g., mouse, keyboard, etc.) and/or application modules (e.g., plug-ins, GPS, etc.). In an aspect, thescripting362 component may include a JavaScript® engine configured to compile and/or execute JavaScript® code.
• Inblock354, thebrowser system350 may perform a fetch operation to request/receiveprogramming instructions356 from a server in the Web352 (e.g., via HTTP). Inblock358, thebrowser system350 may translate/decode the receivedprogramming instructions356 to generateHTML code360. The generatedHTML360 code may include (i.e., embed or include references to) JavaScript® code, the execution of which may generate additional HTML code for insertion into the containing HTML page (e.g., the HTML code in which the JavaScript® is included). Such generated HTML code may affect the behavior and/or presentation of the HTML page. The generatedHTML360 code may also include style sheets and/or CSS code.
• Inblock364, thebrowser system350 may parse theHTML360 code (and embedded/referenced JavaScript® code) to generate a document object model (DOM)366 of the HTML document. TheDOM366 may represent the contents, relationships, styles, and positions of various objects in the HTML code. Communications between browser “passes” and components may occur via theDOM366. A “browser pass” may be a thread, process, or application associated with a single iteration through relevant portions of the HTML document. In an embodiment, a browser pass may be a “work item.”
• As mentioned above, JavaScript® code may be embedded in HTML code, and at the same time, generate additional HTML code to be inserted into the containing HTML page. To enable the insertion of code (and to ensure proper order) two different processes may be required to interpret, parse, and execute the JavaScript® code and the containing HTML code. Thus, in an aspect, the parse operations ofblock364 may be performed by multiple processes or applications.
• Inblock368, thebrowser system350 may perform style operations to generate a modifiedDOM tree370 by, for example, applying one or more style sheets (e.g., CSS) to the HTML document and/or to the generatedDOM366 tree.
• Inblock372, thebrowser system350 may “solve” thepage layout374 by performing layout operations. In an aspect, the layout operations may be performed so that the page layout is solved incrementally as additional content necessary to display the page becomes available (e.g., is downloaded, processed, and/or added to the DOM).
• Inblock376, thebrowser system350 may perform render operations to displaycontent378 of the HTML document on an electronic display of a computing device.
• The various aspects modify the underlying serial nature of existing browser processing algorithms. Various aspects may include a dynamic and concurrent browser system that supports a high degree of parallelism and/or concurrency. Various aspects may exploit concurrency at multiple levels. Various aspects may perform parallel algorithms for individual browser passes to speed up processing and/or executions times of various browser components and/or operations. Various aspects may overlap browser passes to speed up total execution time.
• FIGS. 4 and 5 illustrate example components, information flows, and subsystems in anaspect browser system500 suitable for exploiting concurrency at multiple levels in accordance with various aspects.
• FIG. 4 illustrates abrowser system500 that includes a fetchmanager component502, aDOM dispatcher component504, anHTML parser component506, anHTML pre-scanner component508, animage decoder component510, aCSS engine component512, a JavaScript® engine component514, a layout andrendering engine component516, and auser interface component518. In an aspect, thebrowser system500 may also include a sandboxed JavaScript® engine component530. Each of these components502-530 may be a software module (e.g., a process running on a processor, a thread of execution, a thread pool, a program, etc.). In various aspects, any or all of the components502-530 may utilize a thread library (e.g., Pthreads, etc.) or a parallel task library (e.g., Intel Thread Building Blocks, Cilk, etc.) to support concurrency.
• In an aspect, thebrowser system500 components502-518,530 may be loosely coupled and configured to support concurrency.
• The fetchmanager component502 may be configured to fetch resources from the network, perform cache management for fetched resources, and provide notifications for the arrival of data from the network to other browser components. In an aspect, the fetchmanager component502 may be configured to fetch resources in the order in which they appear in the HTML document (i.e., without imposing any priorities). In another aspect, the fetchmanager component502 may be configured to assign priorities and/or fetch resources based on pre-assigned priorities.
• TheDOM dispatcher component504 may be configured to schedule DOM updates, serialize access to the DOM tree, and manage the interaction between the various browser components. The other subsystems (i.e., the rest of the browser infrastructure) may dispatch work items (also called “DOM dispatcher work items”) into a concurrent DOM dispatcher queue. TheDOM dispatcher component504 may be configured to pull the work items from the DOM dispatcher queue, and process the work items one at a time. In various aspects, the work items may include browser passes and/or events (e.g., timer events, events from the user interface, etc.).
• TheHTML parser component506 may be configured to receive incoming (e.g., partial, etc.) data chunks of an HTML document (e.g., via DOM dispatcher work items, etc.), and construct a DOM tree by executing an HTML parsing algorithm (e.g., an HTML5 parsing algorithm, etc.). TheHTML parser component506 may add external resources referenced in the HTML document to a fetch manager queue accessible to the fetchmanager component502. TheHTML parser component506 may also initiate execution of JavaScript® code by calling the JavaScript® engine component514 at appropriate times during the parsing operations.
• TheHTML pre-scanner component508 may be configured to scan the HTML document to quickly determine the external resources that are requested/required by the HTML document. TheHTML pre-scanner component508 may task (e.g., via a notification, memory write operation, etc.) the fetchmanager component502 to begin downloading the external resources and/or performing further processing based on the external resources.
• Theimage decoder component510 may be configured to decode images. For example, when the fetchmanager component502 has received the complete data for an image, it may hand off the image to theimage decoder component510, which may then decode the image for later use.
• TheCSS engine component512 may be configured to calculate the look and feel of the DOM elements for use in later stages (e.g., the layout and rendering stages). Similar to theimage decoding operations564 discussed above, the fetchmanager component502 may hand off CSS style sheets to the CSS engine for parsing and for discovering new resources to be requested.
• In an aspect, theCSS engine component512 may include a CSSresource pre-fetcher component520,CSS parser component522, and aDOM styler component524. The CSSresource pre-fetcher component520 may perform CSS scanning and/or pre-fetching operations, which may include scanning a CSS document to quickly determine what external resources are requested/required by the CSS document. In another aspect, the CSSresource pre-fetcher component520 may task the fetchmanager component502 to begin downloading the external resources and/or performing further processing based on the external resources.
• TheCSS parser component522 may be configured to read CSS code and create a collection of data structures (e.g., CSS rules) in memory. TheDOM styler component524 may be configured to use the data structures created by theCSS parser component522 to determine the style of the nodes in the DOM tree. For each node, theCSS engine component512 may perform rule matching operations to find the rules whose selectors match the node. Such rule matching operations may return many (and sometimes conflicting) rules per node. In various aspects, theCSS engine512 may be configured to use cascading operations to assign weights to rules and choose the rules with the greatest weight.
• The JavaScript® engine component514 may be configured to compile and execute JavaScript® code. The fetchmanager502 may download JavaScript® scripts and send them to the JavaScript® engine component514 to be compiled. TheHTML parser506 and/or theDOM dispatcher504 may request that the JavaScript® engine component514 execute scripts.
• The JavaScript® engine component514 may include a thread pool for compilation tasks/operations, and may be configured to compile multiple scripts (JavaScript® code) in parallel. Due to JavaScript® semantics, in an aspect, the execution of scripts may be performed sequentially in the main engine thread. In an aspect, the JavaScript® engine component514 may be configured so that, when theHTML parser506 or the DOM dispatcher504 (e.g., for user interface events) requests the JavaScript® engine component514 to execute a script that has not been compiled, the JavaScript® engine component514 automatically initiates compilation of the scripts and waits for the results of the compilation before attempting to execute the requested script.
• In various aspects, the JavaScript® engine component514 may include alight compiler526 and a full compiler528 (e.g., to support adaptive compilation and execution of the JavaScript® code). Thelight compiler526 may be configured to generate executable code for infrequently reused JavaScript® code and/or optimized for page load. Thefull compiler528 may be configured to generate higher quality code for heavily reused JavaScript® code and/or optimized for interactivity and web applications. In various aspects, the slower code generation of thefull compiler528 may be amortized between multiple runs of the reused code. Compared to thelight compiler526, thefull compiler528 may achieve significant speedup for iterative web applications. For example, using thefull compiler528, an N-body simulation web application may run faster by a factor of six.
• The sandboxed JavaScript® engine component530 may be an isolated JavaScript® engine that is separate from the primary JavaScript® engine component514. The sandboxed JavaScript® engine component530 may include all the components, features, and functionality JavaScript® engine component514.
• The layout andrendering engine component516 may be configured to transform the styled DOM tree into a viewable web page. In an aspect, the layout andrendering engine component516 may be configured to reflect changes to the DOM and/or CSS style sheets on the electronic display of the mobile device so that the user can view and interact with an updated HTML document. The changes to the DOM and/or CSS may be due to the fetchmanager component502 delivering new resources, theHTML parser component506 updating the DOM, as a result of a JavaScript® engine component514 computation, etc.
• In an aspect, the layout andrendering engine516 may be configured to take a snapshot of the DOM information and perform the layout and/or render operations asynchronously. In another aspect, the layout andrendering engine516 may be configured to invoke layout and/or render operations synchronously (e.g., when JavaScript® makes use of APIs that query layout information).
• Theuser interface component518 may be configured to manage interactions between thebrowser system500 and a mobile device user. Theuser interface component518 component may translate user interactions (e.g., touching a link on the electronic display of a mobile device) into function/method calls (e.g., Java Native Interface or “JNI” method calls) that create work items for placement in the DOM dispatcher queue.
• In an aspect, all the above-mentioned components502-518,530 may instantiated once for each webpage. In another aspect, the fetchmanager component502 and the layout andrendering engine component516 may be global, whereas the other components (e.g.,504,506,508,510,512,514, and518) may instantiated once for each webpage or HTML document.
• FIG. 5 illustrates example subsystems and information flows in theaspect browser system500 discussed above. Specifically,FIG. 5 illustrates that thebrowser system500 may include auser interface subsystem552, aresource manager subsystem554, a per-pageDOM engine subsystem556, a per-page JavaScript® engine subsystem558, and arendering engine subsystem560.
• Each of the subsystems555-560 may be loosely coupled and configured to support concurrency. The subsystems552-560 may be implemented as software modules (e.g., a process running on a processor, a thread of execution, a program, etc.). The operations of the subsystems552-560 may be performed by one or more of the components discussed above with reference toFIG. 4 and/or on any single or multiprocessor computing system.
• In an aspect, theresource manager subsystem554 andrendering engine subsystem560 may be instantiated once (e.g., may be global), and the per-pageDOM engine subsystem556 and the per-page JavaScript® engine subsystem558 may be instantiated once for each webpage or HTML document.
• Theuser interface subsystem552 may be configured to perform various operations for managing user interactions with the browser system550, including translating user interactions (e.g., touching a link on the electronic display of a mobile device) into function/method calls that create work items for placement in a DOM dispatcher queue, detecting and/or sending events to the correct instance of the per-page JavaScript® engine subsystem558, and/or sending uniform resource locator (URL)/uniform resource identifier (URI) information to the resource manager subsystem554 (e.g., via a memory write operation, function call, etc.).
• Theresource manager subsystem554 may be configured to performpre-fetching operations562, HTMLpre-scanning operations563,image decoding operations564, CSS scanning/pre-fetching operations566, and JavaScript scanning/pre-fetching operations567. By way of example, these operations may be performed by the fetchmanager502, theHTML pre-scanner508, theimage decoder510, theCSS engine512, and/or theJavaScript engine514,530 components, or by any combination of the components discussed above with reference toFIG. 4.
• Thepre-fetching operations562 may include requesting/receiving resources and/or programming instructions from a web server corresponding to the URL/URI, translating or decoding the received programming instructions to generate HTML, and sending the generated HTML code to the correct instance of the per-page JavaScript® engine subsystem558 (e.g., via a memory write operation, etc.).
• The generated HTML code may embed and/or reference JavaScript® code, CSS code, images, and various other resources. Resources most commonly referenced in an HTML document are images, CSS style sheets, and JavaScript® sources. Style sheets and JavaScript® sources may also reference further external resources. In an aspect, the generated HTML code may be scanned so that all references identified by the HTML document (including the embedded or referenced style sheets and JavaScript® sources) may be fetched in advance (e.g., as part of the pre-fetching operations562).
• The HTMLpre-scanning operations563 may include scanning the generated HTML code to quickly discover requested/required external resources, and informing a fetch manager and/or pre-fetcher that it may begin downloading the external resources and/or performing further processing based on the discovered external resources. In an aspect, the downloading of external resources may be performed as part of the pre-fetching562 operations discussed above. In an aspect, the HTML pre-scanner operations and thepre-fetching operations562 may be performed concurrently (e.g., in separate threads/processes).
• Theimage decoding operations564 operations may include decoding images for later use by therendering engine subsystem560. Theimage decoding operations564 may be performed in response to determining that the complete data set for an image has been downloaded (e.g., via a memory write operation performed as part of the pre-fetching562 operations, etc.) and/or in response to receiving a notification (e.g., from a fetch manager component502). In an aspect, theimage decoding operations564 may be performed concurrently with the HTMLpre-scanning operations563 and thepre-fetching operations562.
• The CSS scanning/pre-fetching operations566 may include scanning CSS style sheets embedded in (or referenced by) the generated HTML code to quickly discover requested/required external resources requested by the CSS style sheets. In an aspect, the CSS scanning/pre-fetching operations566 may include informing a fetch manager and/or pre-fetcher that it may begin downloading the discovered external resources. In an aspect, the CSS scanning/pre-fetching operations566 may include initiating the downloading of the discovered external resources. In an aspect, the CSS scanning/pre-fetching operations566 may be performed in the CSS engine component512 (e.g., by the CSS resource pre-fetcher520) in response to the fetchmanager component502 sending one or more CSS style sheets to theCSS engine component512. In an aspect, the CSS scanning/pre-fetching operations566 may be performed concurrently with theimage decoding operations564, the HTMLpre-scanning operations563, and thepre-fetching operations562.
• The per-pageDOM engine subsystem556 may be configured to performHTML parsing operations568,CSS parsing operations570,timer operations572,styling operations574, and operations to manageevents576. In an aspect, the operations of the per-pageDOM engine subsystem556 may be performed concurrently with the operations of theother subsystems552,554,558,560.
• TheHTML parsing operations568 may include parsing the received HTML code, separating the HTML markup tags from the substantive content, and/or generating a DOM of the received HTML code. TheHTML parsing operations568 may also include identifying external resources referenced in the HTML document so that the identified external resources may be downloaded by the fetchmanager502 and/or as part of thepre-fetching operations562. TheHTML parsing operations568 may further include initiating execution of JavaScript® code (e.g., by invoking the execution operation578) during the parsing of the HTML code (e.g., as JavaScript® is discovered, etc.).
• TheCSS parsing operations570 and thestyling operations574 may include applying one or more CSS style sheets to the generated DOM tree (or generating a modified DOM tree based on CSS style sheets). In various aspects, any or all of theHTML parsing operations568,CSS parsing operations570, andstyling operations574 may be performed concurrently.
• Thetimer operations572 may include managing or responding to events and/or conditions relating to timers and/or timer classes (e.g., System.Timers).
• Theevents576 operations may include managing various events, such as timer events and user interface events (e.g., an event generated in response to a user touching a link on the electronic display of a mobile device).
• The per-page JavaScript® engine subsystem558 may be configured to perform JavaScript® execution operations578 and JavaScript® compilation operations580.
• In various aspects, the per-pageDOM engine subsystem556 and/or theresource manager subsystem554 may be configured to send JavaScript® code embedded in (or referenced by) the HTML code to the correct instance of the per-pageJavaScript® engine558 for compilation and/or execution (i.e., via theexecution578 andcompilation580 operations). In aspect, theJavaScript® engine558 may update/modify the generated DOM tree based on the results of the JavaScript® compilation and/orexecution operations578,580.
• Therendering engine subsystem560 may be configured to performlayout operations582 and renderoperations584. For example, therendering engine subsystem560 may receive (e.g., via memory writes, calls, notifications, etc.) a DOM tree and/or layout tree from the per pageDOM engine subsystem556, solve the page layout (via the layout operations582), and display the content on an electronic display of a computing device (via the render operations584). In an aspect, performinglayout operations582 may include solving the page layout incrementally as additional content becomes available (e.g., is downloaded, processed, and/or added to the DOM tree) to therendering engine subsystem560. In various aspects, any or all of thelayout operations582 and/or renderoperations584 may be performed concurrently.
• As discussed above with reference toFIGS. 4 and 5, theHTML parser506 and/or theCSS parser522 may discover external resources (images, audio, CSS, JavaScript®, etc.) requested/required for rendering the HTML document and request that the discovered resources be downloaded, such as via the fetchmanager502 and/or as part of the pre-fetch operations.
• Mobile devices may experience high latency times when downloading resources discovered in HTML and CSS code/content. For example, due to idiosyncrasies in the HTML5 specification, an HTML parser must wait for a script element (e.g., <script> blocks) to finish executing before it can continue parsing the remaining portions of the HTML document. Thus, if a web page references an external resource after a script element, the operation of fetching that resource cannot be overlapped with the operation of waiting for script element to finish execution. This often increases the time required to download and display a webpage.
• In various aspects, thebrowser system500 may be configured to speculatively parse ahead of the script elements to discover new resources without waiting for the script element to finish execution. In these aspects, thebrowser system500 may be forced to discard some of the results of the speculative parsing (e.g., when JavaScript® inserts new content into the DOM tree via the document.write API, etc.).
• In an aspect, thebrowser system500 may be configured to perform aggressive resource pre-fetching operations to discover the requested/required resources as early as possible and request multiple resources to be fetched/downloaded in parallel. In this manner, the various aspects may prevent thebrowser system500 from being forced to discard some of the results of speculative parsing, and may mask network latencies, utilize more of the available bandwidth, and reduce the overall time spent waiting for resources to arrive.
• Thebrowser system500 may be configured to perform aggressive resource pre-fetching operations, which may include speculative resource prefetching via sandboxed execution. In various aspects, these aggressive resource pre-fetching operations may performed as part of the HTMLpre-scanning operations563,CSS pre-fetching operations566, or both.
• Referring toFIGS. 4-5, the HTMLpre-scanning operations563 performed in furtherance of the aggressive resource pre-fetching operations may include obtaining all “id”, “class”, and/or “style” attributes in the HTML document, quickly discovering external resources referenced in the HTML document, and triggering the downloading of the discovered resources from the network. TheHTML pre-scanner508 may “approximately parse” the HTML in order to discover resources, without performing any of the substantive or computationally intensive processing (e.g., construction the DOM tree) that is required from theHTML parser506. By forgoing these complex parsing operations, the HTMLpre-scanning operations563 may be performed concurrent with (and run ahead of) theHTML parsing operations568, and do not have to wait for the script elements to finish execution.
• In an aspect, network packets may be sent to the HTML pre-scanner508 and theHTML parser506 independently, as they arrive. In an aspect, the time spent waiting for resources to arrive may be further reduced by performing HTMLpre-scanning operations563 in parallel to the (non-speculative) HTML parsing570 operations.
• As discussed above, theweb browser system500 may include aCSS parser522 configured to quickly scan a CSS document and aCSS resource pre-fetcher520 configured to perform CSS pre-fetching operations. In an aspect, CSS style sheets may be dispatched to a thread pool responsible for parsing CSS concurrently. If a CSS rule contains further external resources, the CSS resource parser may make a decision regarding whether to initiate prefetching for the further external resources based on the likelihood that they are actually referenced in the HTML document. In an aspect, theCSS resource pre-fetcher520 may be configured to download (or initiate the downloading of) a specific range/number of referenced resources (downloading too few resources may mean that more new resources will be discovered by theDOM styler524 when styling the DOM tree later on, which may result in additional latencies).
• It is common practice among websites to reference many more resources than are actually needed for any given document by, for example, using a site-wide common style file. Downloading all included resources may consume excess bandwidth and slow down page loading. In various aspects, theCSS parser522 may be configured to employ the “id” and “class” attributes discovered by theHTML pre-scanner508 to determine whether a CSS rule is likely to be matched. If all of the attribute values referenced in a CSS rule selector have been seen/evaluated by theHTML pre-scanner508, it may be determined that the rule is likely to match at least one DOM tree element, and thebrowser system500 may initiate the downloading of the resources corresponding to the CSS rule. This “CSS rule” heuristic is very effective, and wrong decisions do not have a significant negative impact on the operations of thebrowser system500. Missed resources may be discovered during the DOM styling phase (via the DOM styler component524) at the cost of the latency required to download the resource.
• In an aspect, theHTML pre-scanner508 may be configured to identify and/or discover resources that may be discovered without having to execute JavaScript®.
• As discussed above, mobile devices may experience high latency times when downloading resources discovered in HTML and CSS code/content due to idiosyncrasies in the HTML5 specification, such as the HTML parser being required to wait for a script element (e.g., <script> blocks) to finish executing before it can continue parsing. In addition, modern web documents (e.g., HTML pages, HTML documents, etc.) may reference a large number of external resources, and each external resource may include references to other external resources. For example, HTML documents typically include references to various external resources, such as images, audio, Cascading Style Sheets (CSS), and JavaScript®, and the referenced resources (e.g., CSS, JavaScript®) may further include references to additional external resources (e.g., images, audio, etc.).
• The document load time (i.e., time from requesting a document until it is ready to be displayed on screen) is dominated by input/output costs (e.g., network transfers of needed resources). The minimal document load time needed to load all required resources is constrained by the bandwidth of the connection between resource storage and computing device. Also, transferring document resources to the displaying device incurs a latency cost. Various aspects may be configured to start resource transfers as early as possible to better utilize the available bandwidth, overlap transfer latencies, and improve document load times.
• As mentioned above, since not all of the referenced external resources are required (or even used) to render a given webpage, recursively downloading all of the referenced resources may waste a significant amount of bandwidth and power. In addition, when any of the resources are not immediately available, the browser must wait until it receives and analyzes those resources before the page can be properly rendered. This increases the amount of time that is required to load and/or render the webpage (e.g., document load time), and degrades the user experience.
• Conventional solutions attempt to speed up rendering of web pages using techniques such as caching portions of web pages in memory to reduce the information that must be downloaded the next time the page is accessed. However, using conventional solutions, a web browser cannot identify the external resources that are required to render a web page for the first time without first analyzing the entire document (i.e., webpage), requesting and receiving most (if not all) of the resources referenced in the document and subdocuments, and analyzing the received resources. Thus, using conventional solutions, the precise set of resources required by the document cannot be determined until after the entire document has been fully analyzed.
• To overcome these limitations of existing solutions, various aspects may utilize speculation/prediction techniques to identify resources required to render a web page or document before the entire document has been analyzed.
• Generally, speculatively predicting whether a resource is required (based on an incomplete set of information) results in one of four possible outcomes: a true positive; a true negative; a false positive; and a false negative. A true positive outcome is when a resource was speculatively downloaded and was later actually required. A true negative outcome is when the resource was not speculatively downloaded but was not required. A false positive outcome is when a resource that isn't required is speculatively downloaded (which wastes bandwidth and energy) and a false negative outcome is when the resource is not speculatively downloaded but is required (thus there is nothing gained with respect to this resource from the speculative preprocessing).
• The true positive and true negative outcomes are beneficial and desired because such decisions improve the user experience by reducing page load times. However, false positive and false negative outcomes are disadvantageous. For example, a false negative may result in a resource being requested during the rendering of a document (e.g., HTML document), which may extending document load times until the resources is available. Since the resource is not required for the browser to properly render the document, it is a waste of computing and network resources (bandwidth, processing, etc.).
• Various aspects include web browser systems configured to perform speculative resource downloading operations based on heuristics to maximize the number of true positives and true negative while minimizing the number of false positive and false negative download decisions.
• FIG. 6 illustrates an aspect browser method600 of processing an HTML document to discover the external resources (images, audio, CSS, JavaScript®, etc.) required for proper rendering of the webpage and pre-fetching the discovered resources in advance of the page loading/rendering operations. The operations of method600 may be performed by a processor of a single or multiprocessor computing system executing a suitably configured web browser.
• Referring toFIG. 6, inblock602, a web browser may initiate or invoke a scan operation (e.g., via theHTML pre-scanner508,CSS engine512, etc.) to scan the HTML document and/or CSS documents for the structural information and/or to discover resources. In an aspect, the scan operation may be performed as part of the HTMLpre-scanning operations563. In an aspect, the scan operation may be performed as part of theCSS scanning operations566. In various aspects, the scan operation may be executed concurrent with, and independent of, the HTML andCSS parsing operations568,570. In various aspects, the scan operation may be performed by a process, thread, application, a work item, and/or browser pass.
• Inblock604, the scan operation (e.g., HTML and/or CSS scanning operations) may determine (i.e., predict, speculate) which of the discovered resources are likely to be required. Inblock606, the scan operation may issue resource requests (e.g., via a memory write operation, etc.) to a browser fetch component (e.g., to the fetch manager502) to begin downloading resources determined to have a high probability of being required. In an aspect, as part ofblock606, two or more resource requests may be issued (or sent) in parallel or concurrently. In an aspect, each resources request may spawn a new process and/or be processed by a different thread of execution. Inblock608, the scan operation may continue scanning the HTML document and/or CSS documents to discover additional required resources. The operations in blocks604-608 may be repeated until all external resources are discovered and/or the entire HTML document is scanned.
• Inblock610, the web browser may initiate or invoke a fetch operation (e.g., via the fetch manager502) to download one or more resources identified by the resource request (e.g., resource request issued by the scan operation in block606).
• Inblock612, the web browser may scan the downloaded resources to discover additional references to external resources. As part ofblock612, the web browser may initiate or invoke a new process or thread of execution to perform the scanning operations. In an aspect, as part ofblock612, the web browser may initiate or invoke aCSS scanning operation566. In an aspect, as part ofblock612, the web browser may initiate or invoke an HTML scanning operation orHTML pre-scanning563 operation.
• Inblock614, the web browser may determine (i.e., predict, speculate) the discovered resources that are likely to be required based on scanning the downloaded resources. Inblock616, the web browser may issue additional resources requests (e.g., via a memory write operations, etc.) to a browser fetch component (e.g., to the fetch manager502) to being downloading resources determined to have a high probability of being required. In an aspect, each of these additional resource requests may spawn other processes and/or may be processed by a different process or thread of execution. The operations in blocks610-616 may be repeated until all external resources are discovered and/or downloaded. In an aspect, the operations of blocks602-608 may be performed in parallel with the operations in blocks610-616.
• Unlike conventional HTML parsers, the scan operations discussed above with reference toFIG. 6 do not perform error correction on the scanned HTML document or execute encountered JavaScript® code. This enables the scan operations to be performed quickly. Also, unlike conventional HTML parsers, the scan operations discussed above may be executed in parallel or concurrently (e.g., in independent threads or processes, etc.), which enables the various aspects to more fully utilize multiprocessor architectures prevalent in modern computing devices. Additionally, the scan processes discussed above may scan resources referenced in the HTML document (e.g., CSS documents), which is also not performed in conventional HTML parsers.
• Generally, if a scan operation (e.g., HTMLpre-scanning operations563,CSS scanning operations566, etc.) only scans the structure of the HTML document, it is likely to correctly speculate regarding the resources that are required (i.e., produce only true positives) unless, for example, there are structural errors in the document (since the scanner does not perform error correction) or embedded JavaScript® code in the document that makes alterations to the document as it is parsed (since the scanner does not execute JavaScript®).
• In an aspect, to maximize the number of true positives and true negatives, the scan operations (e.g., HTMLpre-scanning operations563,CSS scanning operations566, etc.) may identify the resources that are likely to be required using information obtained during the initial scan of the HTML document.
• FIG. 7A illustrates anaspect browser method700 of using speculation techniques and heuristics to discover document resources for speculative downloading. The document resources may include images, CSS files, JavaScript® scripts, etc. Thebrowser method700 enables a HTML document scanner and a plurality of CSS documents scanners to execute in parallel, intelligently identifies the resources that are likely to be required, reduces the number of false negatives that result from the speculative resource requests and/or pre-fetching operations. In an aspect, thebrowser method700 may utilize a heuristic (e.g., a “CSS rule” heuristic) to minimize the number of false positives.
• Inblock702 ofbrowser method700, an HTML document scanner (e.g., HTML pre-scanner508) may begin scanning a HTML document to discover resources and obtain all URL/URIs, and HTML “id”, “class”, and/or “style” attributes associated with (or mentioned by) HTML elements included the HTML document. The HTML document scanner may be independent of, and/or execute in parallel with, an HTML parser.
• Inblock704, the HTML document scanner may encounter an external resource referenced by URL/URI's and/or HTML elements included in the HTML document. Inblock706, the HTML document scanner may issue a request (e.g., to a fetch manager) to download encountered resources referenced in the HTML document. In an aspect, the HTML document scanner may be configured to invoke the downloading and/or parsing of each encountered external CSS resource (e.g., as the external resources are encountered by the scanner, etc.). In an aspect, the downloading of an external CSS resource may cause a CSS document scanner (e.g.,CSS engine512, etc.) to begin scanning the CSS document.
• Inblock708, the HTML document scanner may encounter and/or collect HTML id, class, and style attributes. Inblock710, the HTML document scanner may send the encountered/collected information (i.e., information pertaining to the collected id, class, and style attributes) to a CSS document scanner. In an aspect, sending the collected information may include sending every encountered and/or identified HTML id, class, and style attribute to the CSS document scanner.
• Inblock712, the HTML document scanner may continue scanning the HTML document to discover additional resources. Indetermination block714, the HTML document scanner may determine whether it has finished scanning the HTML document. When the HTML document scanner determines that it has finished scanning the HTML document (i.e., determination block714=“Yes”), inblock716, the HTML document scanner may notify a CSS document scanner (e.g.,CSS engine512, a process performing theCSS scanning operations566, etc.) that it has finished scanning the HTML document (e.g., via a memory write operation, method call, notification, etc.). When the HTML document scanner determines that it has not yet finished scanning the HTML document (i.e., determination block714=“No”), inblock702, the HTML document scanner may continue scanning the HTML document to discover additional resources.
• Inblock719 ofbrowser method700, the CSS document scanner may begin scanning a CSS document for external resources. Initiation of a CSS document scanner inblock719 may be triggered by availability of a CSS document obtained by a fetch manager (e.g., in response to operations performed as part ofblock706, etc.). In an aspect, the scanning of CSS documents may be performed in parallel with the scanning of the HTML document (e.g., operations in blocks702-716). Thus, the CSS document scanner may scan received CSS documents to identify external resources referenced in those documents while the HTML document scanner continues to scan the HTML document (e.g., identifying additional CSS documents for download, etc.). Further, there may be multiple CSS document scanners executing in parallel (e.g., when multiple CSS documents are downloaded).
• Inblock720, the CSS document scanner may receive information pertaining to HTML id, class, and/or style attributes from the HTML document scanner. Inblock721, the CSS document scanner may determine whether the received information marks or identifies a CSS rule and/or external resource (associated with the received HTML id, class, and/or style attributes) as likely to be required and/or used by the HTML document. In aspect, as part ofblock721, the CSS document scanner may determine whether every HTML id, class, and/or style attribute associated with a CSS rule has already been encountered by the HTML document scanner.
• Indetermination block722, the CSS document scanner may determine whether the CSS rule and/or external resource (associated with the received HTML id, class, and/or style attributes) is likely to be required and/or used by the HTML document. In an aspect, as part ofdetermination block722, the CSS document scanner may determine whether every URL/URI, and HTML id, class, and/or style attribute mentioned by the HTML document has already been encountered.
• When the CSS document scanner determines that the CSS rule and/or external resource is likely to be required and/or used by the HTML document (i.e., determination block722=“Yes”), inblock724, the CSS document scanner may immediately request the resources referenced by that CSS rule to be downloaded, such as by performing a memory write operation and/or notifying the fetchmanager502.
• In an aspect, the CSS document scanner may determine that the CSS rule and/or external resource is likely to be required when it is determined that every URL/URI, and HTML id, class, and/or style attribute, mentioned by the HTML document has already been encountered.
• When the CSS document scanner determines that the CSS rule and/or external resource is not likely to be required and/or used by the HTML document (i.e., determination block722=“No”), inblock723, the CSS document scanner may store in memory information pertaining to the CSS rule (e.g., the received HTML id, class, and/or style attributes) in a list of resource references. Inblock725, the CSS document scanner may continue scanning the CSS document, if necessary (e.g., when there are additional elements to be scanned/processed, etc.).
• Inblock726, the CSS document scanner may receive a notification from the HTML document scanner indicating that the HTML document scanner has finished scanning the HTML document. Inblock727, the CSS document scanner may retrieve information pertaining to a CSS rule from the list of resource references stored in the memory and evaluate the retrieved information.
• Indetermination block728, the CSS document scanner may determine whether the retrieved information marks/identifies a CSS rule and/or external resource being required (or likely to be required) by the HTML document. In aspect, as part ofdetermination block728, the CSS document scanner may determine whether every HTML id, class, and/or style attribute associated with the retrieved CSS rule has already been encountered and/or processed by the HTML document scanner.
• When the CSS document scanner determines that retrieved information marks/identifies a CSS rule and/or external resource is likely to be required and/or used by the HTML document (i.e., determination block728=“Yes”), inblock729, the CSS document scanner may request downloading of the resources corresponding to that CSS rule. In this manner, the number of false negatives caused by scanning the HTML document and the CSS documents at the same time may be minimized. In addition, the various aspects may decrease document load times (and hence, increase responsiveness) with little or no increase in data transfer costs, as well as less power consumption due to reduced utilization of the processor and network interface/radio.
• Returning toFIG. 7A, when the CSS document scanner determines that retrieved information does not mark or identify an external resource as being required (or likely to be required) by the HTML document (i.e., determination block728=“No”), inblock721, the CSS document scanner may retrieve the next rule from memory. The operations of blocks720-722 may be repeated until all the CSS rules stored in the memory by the HTML document scanner have been evaluated.
• In various aspects, more precise heuristics than the CSS rule described above may be used by the HTML document scanner and/or CSS document scanner to improve performance. For example, in an aspect, the HTML document scanner may be configured to scan embedded JavaScript® code for URLs and/or commands that could modify the HTML document. Similarly, in an aspect, the CSS document scanner may be configured to record hierarchical information about the HTML tags associated with each encountered ID, which may allow the CSS document scanner to identify and reject more potential false positives.
• In conventional browsers, the HTML parser is generally responsible for identifying all of the external resources and requesting them from severs via the network. As discussed above, when these resources are explicitly specified in the HTML document, various aspects may pre-fetch these resources and issue the request much earlier in the page load than conventional browsers. In addition, various aspects may pre-fetch and/or process the resources in parallel.
• Software developers are increasingly using scripts (e.g., JavaScript® Code®) to dynamically determine the resources that are going to be required for a particular application-device combination (e.g., web browser-mobile device combination). For example, scripts may evaluate various factors relating to the client (e.g., browser) and computing device to identify the resources that are to be downloaded. Such scripts may essentially build a URL dynamically for a resource (e.g., images, CSS, other JavaScript®, etc.) based on the evaluated factors. Thus, an HTML document may require resources that are not explicitly identified in the HTML document, and which may only be determined by executing JavaScript® code included in the HTML document.
• Since the JavaScript® code may change the state, behavior, and/or presentation of the containing HTML (and the HTML code itself), the HTML parser is required to execute the encountered JavaScript® code (or scripts) sequentially and/or by following ordering rules defined in the HTML specifications. For example, when an HTML parser encounters a script tag (i.e., a <script> tag used to define a client-side script, such as a JavaScript® script), the HTML parser has to wait for the script to be downloaded and executed before it may continue parsing the remaining portions of the HTML document. As a result, all resource requests may be serialized (i.e., required to be performed one after the other) within the execution of the JavaScript® script (i.e., JavaScript® code inside <script> tags). Also, it may be more difficult for the HTML document scanning operations (e.g., HTMLpre-scanning operations563, etc.) to statically predict the resources that are going to be required for proper rendering the webpage.
• Various aspects may overcome these and other limitations by speculatively pre-fetching resources in a sandboxedJavaScript® engine530, which enables thebrowser system500 to discover and download resources not explicitly requested in the HTML document in parallel to other browser operations (e.g., HTML parsing) and other resource requests. These aspects may also enable thebrowser system500 to execute multiple JavaScript® scripts in parallel without unintentionally modifying the browser state.
• Various aspects may execute scripts (e.g., JavaScript® code) as soon as they are discovered, in parallel with other browser operations (e.g.,HTML pre-scanning563, HTML parsing568, etc.) and/or other scripts. In order to avoid interfering with the normal processing of the webpage, the scripts may be executed in a sandboxedJavaScript® engine530 that is isolated and/or separated from the other browser components (e.g., so as not to affect the operations of primary JavaScript® engine). Executing the scripts in a sandboxedJavaScript® engine530 prevents the system from unintentionally modifying the browser state during the parallel execution of scripts. In an aspect, each script may be executed in a separate instance (e.g., thread) of the sandboxedJavaScript® engine530.
• Various aspects may modify the API between the browser client and theJavaScript® engine530.
• Generally, scripting engines (e.g.,JavaScript® engine514,530,558) provide bindings (i.e., API for mapping languages) to the browser API (i.e., interface that enables the scripts to invoke browser operations) to invoke browser operations (e.g., manipulating DOM, accessing network, etc.).
• In an aspect, theJavaScript® engine530 may monitor browser APIs that request resources from the network. TheJavaScript® engine530 may modify the bindings (or provide a separate set of bindings for the scripting engine) to cause the resource requests to be redirected to a different browser component, such as a pre-fetcher component. In this manner, the resource requests and/or collected information may be passed directly to the pre-fetcher component for further processing.
• The sandboxed JavaScript® engine may scan through the JavaScript® code and execute only select portions of code and/or select operations most relevant to discovering external resources. Since the scanning operation is only concerned with discovering resources that the script may request, the scanning operation is not bound by the HTML specification rules, and does not have to run/execute all of the encountered code. By not fully executing all of the encountered code, the JavaScript® scanning operations may be performed quickly by the sandboxed JavaScript® engine.
• The sandboxed JavaScript® engine may apply heuristics to further speedup the JavaScript® scanning operations. By way of example, such heuristics may include limiting the total execution time (e.g., spend a maximum of 10 ms per script or operation, etc.), the number of loop iterations (e.g., only process the first 10 iterations of a loop, etc.), the recursion depth, the supported features, abstract interpretation, etc.
• Various aspects may limit the sizes of object and data structures (e.g., hash tables, arrays etc.) to further speedup the JavaScript® scanning operations, since such structures generally do not affect resource dependencies.
• Software developers often use common patterns, frameworks, and/or services (herein collectively “patterns”) in their code. Various aspects may detect such commonalities/patterns in the code (e.g. during parse, analyze, compile, etc.) and execute only the patterns (or portions of JavaScript® code identified by the patterns) relevant to discovering resources. In an aspect, instead of full compliance and conservative code generation, the sandboxed JavaScript® engine may be configured to target the most common patterns (e.g., via aggressive compiler optimizations). Patterns may be detected using a wide variety of known pattern recognition techniques, such as detecting keywords in the code (which is a relatively simple operation) and/or analyzing the structure of the page and/or script (which is relatively complex operation).
• FIG. 7B illustrates anaspect method730 of speculatively pre-fetching resources in parallel by parallel processing of scripts in a sandboxed JavaScript® engine. The operations ofmethod730 may be performed in parallel with the other browser operations discussed herein.
• Inblock732 ofmethod730, an HTML document scanner (e.g., HTML pre-scanner508) may begin scanning the HTML document for structural information and/or to discover resources. Inblock734, the HTML document scanner may encounter a JavaScript® script, and send the encountered script (e.g., via a memory write operation, a redirected resource request, modified bindings, etc.) to a sandboxed JavaScript® engine to immediately execute the encountered script. Inblock732, the HTML document scanner may continue to scan the HTML document for structural information and/or to discover resources. In an aspect, the HTML document scanner may generate (or spawn) the sandboxed JavaScript® engine in response to encountering the script.
• Inblock735, the sandboxed JavaScript® engine may begin scanning the script to discover resources. Inblock736, the sandboxed JavaScript® engine may speculatively execute the script (or portions of JavaScript® code included in the script). The speculative execution of the script may include executing only the operations and/or portions of code most likely to be relevant to discovering external resources. In various aspects, the speculative execution operations may be performed in parallel with other browser operations (e.g.,HTML pre-scanning563, HTML parsing568, etc.) and/or in parallel with the execution of other scripts (whether speculative or not).
• In an aspect, the speculative execution of the script may include executing only the portions of JavaScript® code that correspond to a pattern relevant to discovering resources.
• In an aspect, as part ofblock736, the sandboxed JavaScript® engine may perform the speculative execution of the JavaScript® code based on heuristics (e.g., to reduce execution time). Such heuristics may include limiting the total execution time, number of loop iterations, recursion depth, supported features, and/or abstract interpretation of the code.
• In an aspect, as part ofblock736, the sandboxed JavaScript® engine may limit the sizes of data structures (e.g., hash tables, arrays etc.) generated from the speculative execution of the script. Complete data structures may not result in identifying further resources for downloading, so the processing time required to fully generate/populate large data structure can be bypassed.
• Inblock738, the sandboxed JavaScript® engine may discover a resource that is required in order to render the HTML document but that is not explicitly requested in the HTML document. Inblock740, the sandboxed JavaScript® engine may inform (or spawn) a pre-fetcher to retrieve the discovered resource. Inblock742, the sandboxed JavaScript® engine may discard the results of the processing performed inblock736.
• Inblock744, the pre-fetcher may locate the resources discovered by the sandboxed JavaScript® engine inblock738. Inblock746, the pre-fetcher may download the located resource. Inblock748, the pre-fetcher may save the downloaded resource to memory.
• As discussed above, HTML code may both embed JavaScript® code (called “inline scripts”) and include links to JavaScript® code (called “external scripts”). In order to correctly process an HTML document, both the inline and external scripts must be executed in a specific order defined by the HTML standards.
• As multiple scripts are downloaded, parsed, analyzed, and compiled in parallel, the order in which the scripts become ready for execution may be different than the specific execution order defined by the HTML standards. If a script is not ready to execute, but is the next script in the specific execution order defined by the HTML standards, a browser may be required to wait until the script becomes ready for execution before performing any additional processing of the HTML document. Various aspects utilize this wait time to prepare other scripts or resources for execution (which is not regulated by the HTML standards). Multiple scripts and resources may be prepared in parallel and/or during the execution of other scripts.
• In addition, not all of the scripts included (i.e., embedded or linked to) in an HTML document are actually executed, and preparing all the scripts for execution in advance may waste power and processing resources. Various aspects may intelligently select the scripts that are to be prepared for execution.
• By way of example, an HTML pre-fetcher may discover and download all referenced scripts (out-of-order) and an HTML parser may later orchestrate their execution in the correct order, and at the correct point in time of processing the HTML document.
• The final execution order of the scripts must generally be maintained. However, all operations associated with downloading, parsing, analyzing, and compiling the scripts may be performed in parallel and/or out of order.
• In an aspect, scripts included in an HTML document may be prepared for execution in parallel (i.e., with respect to each other) and out-of-order (i.e., with respect to the specific execution order defined by the HTML standards). This may be achieved by generating and/or associating a unique identifier and/or signature with each script. Signatures may be based on the content of the script. Examples of signatures and signing processes suitable for use in various aspects include file offsets (for inline scripts), a message-digest algorithm (e.g., MD5), a secure hash algorithm (SHA), URL of the script, URI of the script, browser cache keys, and/or any of a variety of known signing processes.
• FIG. 7C illustrates anaspect browser method750 of intelligently preparing scripts included in an HTML document for parallel execution. The operations ofmethod750 may be performed by a processor in parallel with the other browser operations.
• Inblock752, an HTML scanner/pre-fetcher may scan an HTML document for structural information and/or to discover resources (images, CSS, scripts, etc.). Inblock754, the HTML scanner/pre-fetcher may discover one or more scripts in an HTML document, and inform an HTML parser (executing in parallel with the HTML scanner) of the discovered scripts. Inblock756, the HTML scanner/pre-fetcher may initiate the downloading of external scripts.
• Inblock758, the HTML parser may generate an identifier (or signature) for each discovered script (both inline and external scripts) and/or associate each discovered script with an identifier. In an aspect, the HTML parser may set the text of the discovered script as its identifier. In an aspect, the HTML parser may associate the URL/URI of external scripts with the external scripts (i.e., may set their URL/URI as their signature), and perform a digest and/or hash algorithm to compute signatures for the inline scripts. If the URL/URI of a script is not available, not unique and/or otherwise does not uniquely identify a script, as part ofblock758, the HTML parser may generate and use a signature to identify that script.
• Inblock760, the HTML parser may send the scripts and their associated identifiers or URL/URI to a JavaScript® engine executing in parallel with the HTML parser (e.g., in a separate thread). Inblock762, the HTML parser may perform various HTML parser operations, such as parsing the HTML to discover other scripts.
• Inblock772, the JavaScript® engine may receive the scripts and associated identifiers, signatures, or URL/URI from the HTML parser. Inblock774, the JavaScript® engine may prepare (e.g., parse, analyze, and/or compile) the received scripts for execution. The preparation operations may be performed out of order and/or in parallel across all received scripts (i.e., multiple scripts may be prepared at once). In an aspect, as part ofblock774, the JavaScript® engine may employ heuristics (e.g., via abstract interpretation) to detect the call graph without executing code, identify the scripts (or functions) that are most likely to be executed based on the call graph, and prepare for execution only scripts determined likely to be executed. Inblock776, the JavaScript® engine may associate information generated during the preparation of a script (e.g., compiled code, etc.) with that script's identifier, signature or URL/URI.
• Inblock764, the HTML parser may identify the next script to be executed (e.g., based on the execution order defined by the HTML standards). Inblock766, the HTML parser may send an identifier, signature or URL/URI of the next script to be executed to the JavaScript® engine. Inblock768, the HTML parser may wait of the result of the execution or a notification that the script has been executed. Inblock770, the HTML parser may continue performing HTML parser operations.
• Inblock778, the JavaScript® engine may receive the identifier, signature, or URL/URI from the HTML parser. Inblock780, the JavaScript® engine may identify the appropriate script based on the received identifier, signature or URL/URI. Indetermination block782, the JavaScript® engine may determine whether the identified script is ready for immediate execution by, for example, determining whether all of the parsing, analyzing, and compiling operations have been performed for that script. If the JavaScript® engine determines that the script is ready for immediate execution (i.e., determination block782=“Yes”), inblock786, the JavaScript® engine may inform the HTML parser of the results of the execution or that the execution is complete.
• When it is determined that the script is not yet ready for immediate execution (i.e., determination block782=“No”), inblock784, the JavaScript® engine may prepare the script for execution using conventional solutions. Inblock786, the JavaScript® engine may execute the script in accordance with the specific execution order defined by the HTML standards. In this manner,method750 prepares the scripts included in an HTML document for execution in parallel (i.e., with respect to each other) and out-of-order (i.e., with respect to the specific execution order defined by the HTML standards), and the scripts are executed in the order defined by the standards.
• FIG. 8 illustrates anaspect browser method800 of processing pre-fetched resources. Inblock802, a web browser component (e.g., via the fetch manager502) may initiate the downloading of a discovered resource (e.g., an image), which may be downloaded/fetched concurrently (or in parallel) with the performance of other browser operations (e.g., HTML parsing, etc.). When all data associated with the discovered resource is downloaded and/or received, inblock804, the downloaded data (e.g., image data) may be sent to a thread pool for decoding. In an aspect, the decoding operations may be performed concurrently with other browser operations.
• Inblock806, the downloaded data (e.g., image data) may be decoded. Inblock808, the decoded data may be added to a DOM dispatcher queue. Inblock810, aDOM dispatcher component504 may serialize updates to the DOM tree and respective tree nodes (e.g., “img” tree node in the case of image data). Inblock812, the resource (e.g., image) may be removed from a processing list (e.g., list of pending images).
• FIG. 9 illustrates example components in aCSS engine512 suitable for use with the various aspects. TheCSS engine512 may be configured to perform three main categories of operations: CSSresource prefetching operations902,CSS parsing operations904, andDOM styling operations906.
• CSS parsing operations904 may include reading the CSS code and creating a collection of data structures (e.g., CSS rules) in memory. The CSS code may be embedded in HTML or linked as separate files, and may be stored on different servers. Traditional CSS engines (e.g., the ones in WebKit or Firefox) may parse CSS sequentially in the main browser thread. Thus, if a page uses embedded CSS, the HTML parser cannot parse the rest of the HTML document until the CSS engine has parsed the style element in the document's header. If a page uses several CSS files, they will all be parsed sequentially, even though there may be underutilized CPU cores. Such CSS parsing serialization (i.e., serial processing of CSS documents) may cause severe slowdowns if the site uses large CSS files. The various aspects may use asynchronous tasks to avoid CSS parsing serialization.
• Referring toFIG. 9, theHTML parser506 may be configured to spawn a CSS parsing570 task for each style element in the DOM tree during a page load operation. Similarly, the fetchmanager502 may spawn a CSS parsing570 task whenever a new CSS file arrives. As a result, multiple CSS parsing570 tasks may execute concurrently with theHTML parser506 and/orHTML parsing operations568.
• Because the total order of style sheets (CSS) and rules (CSS rules) may be a key part of thestyling operations574, thebrowser system500 may be configured to ensure that the total order is the same, as if the all the style sheets (CSS) had been parsed in the order in which the programmer intended.
• In various aspects, each of the parsing tasks or parsingoperations568,570 may receive a unique, sequential parser ID. Thebrowser system500 may then use that ID to recreate the ordering of the style sheets in the document.
• DOM styling operations906 may enable theCSS engine512 to use data structures created by theCSS parser522 to determine the style of the nodes in the DOM tree. For each node, theCSS engine512 may perform rule matching operations to find all rules whose selectors match the node. Rule matching generally returns many (and sometimes conflicting) rules per node. Using cascading, the CSS engine may assign weights to rules and choose the rules with the greatest weight.
• The last step in styling a node may include theDOM styling operations906 creating a style data structure by using the rules selected by the cascading algorithm and attaching it to the DOM. The rule matching and cascading operations may be performed on several nodes in parallel, as long as certain dependencies are enforced.
• The various aspects may respect/enforce existing HTML and JavaScript® semantics during concurrent execution (or overlapping) of multiple browser operations and/or passes. A DOM tree may be the main data structure used by all browser passes. In various aspects, access to the DOM tree (which may be constructed by the HTML5 parser) may be serialized to conform to the HTML5 specification. In addition, to allow for greater parallelism, each passes may be provided access to a private concurrent data structure (i.e., in addition to the DOM tree). In an aspect, this additional data structure may be a layout tree.
• FIG. 10 illustrates an embodiment parallelDOM styling method1000 in which rule matching and cascading operations are performed on several nodes in parallel. Inblock1002, theCSS engine512 may traverse the DOM tree and spawn two different tasks per DOM node: a matching task, and a node styling task. Inblock1004, the matching task may perform rule matching and cascading operations for the DOM node. Inblock1006, the styling task may create the style data structure that describes the DOM node. In block1008, the styling task may attach the style data structure to the DOM tree.
• FIG. 11A illustrates an example DOM tree suitable for use in various aspects.FIG. 11B illustrates an example task directed acyclic graph (DAG) corresponding to the example DOM tree illustrated inFIG. 11A. Specifically,FIG. 11B illustrates how the matching tasks (represented as triangles) may be completely independent of each other and of the styling tasks (represented as squares), whereas the styling tasks are dependent on each other and the matching tasks. Generally, parallel execution of the matching tasks is only limited by the number of processing cores in the computing system.
• As mentioned above, styling tasks may be dependent on each other and/or the matching tasks. Each styling task may be required to satisfy two dependencies before it can execute. First, a styling task may only execute after the matching task working on the same node has completed execution. This is because the styling task builds the style data structure using the rules selected by the matching task. Second, a styling task working on a node may only execute after the styling task working on the node's parent has completed execution. This is because some of the node's style properties may inherit from its parent's. For example, the CSS code p {color: inherit} instructs the browser to render <p> nodes using the same foreground color as their parents.
• The rule matching operations performed by the matching tasks may be expensive in terms of computation, power, latency, etc. For example, if theCSS engine512 needs to determine whether the rule “h1 p div {color:red}” applies to a <div> element E, the matching algorithm may need to find if any of E's ancestors is a <p> element, and whether any of <p>'s ancestors is a <h1> element. This may require walking up the DOM tree all the way to the root, which may be an expensive operation. In addition, a typical website may require more than 400,000 of such DOM tree walks.
• To reduce the number of DOM tree walks, various aspects may include a bloom filter that stores information about the ancestors of a DOM node. The bloom filter may reduce the number of DOM tree walks to the root (A) by 90%, halving the time spent in the styling algorithm.
• A bloom filter may be a large data structure, and theCSS engine512 may be required to copy it for each styling task. Since copying costs may far outweigh the performance gains, various aspects may use a smaller structure than a bloom filter. This may improve browser performance by reducing the number of copy operations and/or reducing the size of the elements copied.
• As described above, various aspects may use element id and class attributes to predict whether an image referenced in the CSS file should be prefetched. In an aspect, these elements and attributes may be stored in a database that records how many times each of them appears in the document. The HTML parser may also add information to this database.
• Before the rule matching algorithm starts, theCSS engine512 may sort the items in the database according to their frequency. Thebrowser system500 may then assign a bit to each item in a bitmap data structure (referred to as “matching bitmaps”). If the number of ids and classes is larger than the bitmap size, a single bit may be assigned to multiple items. Since these bitmaps are small, they may be copied many times without significantly impacting the performance of the computing device.
• During rule matching operations, each styling task may receive a matching bitmap from its parent. The matching bitmap may record the ids, classes, and tags of its ancestors. Styling tasks may use the matching bitmap to filter out rules that could never match. Afterward, the styling tasks may add their node's id, class, and tag to it and send a copy to their descendants. On average, such matching bitmaps avoid 90% of the walks to the root of the DOM tree, with only 0.024% of false positives.
• False positives may occur because matching bitmaps do not record the order in which labels and ids are encountered. For example, to determine whether the rule “h2 h1 p {color: red}” applies to a certain node <p>, and that the matching bitmap indicates that both <h1> and <h2> are <p>'s ancestors, thebrowser system500 may be required to walk up the DOM tree to check whether <h2> is <h1>'s ancestor. If that is not the case, then it is a false positive situation. Such false positives may not cause the page to render incorrectly, but may waste CPU cycles.
• In an aspect, layout and rendering operation, such as by arendering engine subsystem560, may include performing computations that transform a styled DOM into a bitmap image for display on the screen. The DOM and the CSS styles applied to the bitmap image may be combined to form a new tree structure (called a layout tree), in which each node represents a visual element on the web page. Each DOM node may be translated into zero, one, or many layout tree nodes. Therendering engine subsystem560 may take a layout tree as input and compute the region of the page that each element occupies. The style of each element may be viewed as a constraint for layout (e.g., inline/block display, float, width, height, etc.).
• Therendering engine subsystem560 may traverse the layout tree and solve the constraints (e.g., as part of the layout operations582) to determine the final width, height, and position of each element. Therendering engine subsystem560 may also walk (e.g., as part of the render operations584) over the layout tree (which may be annotated with the results of the layout engine's computations) and draw it on the screen according to the rules of CSS.
• Since thelayout operations582 and rendering operation are closely related and operate together in a pipeline fashion, in an aspect, they may be performed by a single component, such as the layout andrendering engine516.
• In various aspects, therendering engine subsystem560 may be configured to perform thelayout operations582 so that the CSS layout algorithm is performed in four passes over the layout tree. In each pass, information may flow through the tree in a more controlled way than in conventional approaches, exposing the potential for parallelism in the layout process.
• In an aspect, therendering engine subsystem560 may perform four passes on the layout tree: a minimum or preferred width calculation pass, a width calculation pass, a block-formatting context flow pass, and an absolute position calculation.
• The first pass (i.e., the minimum or preferred width calculation pass) may be a bottom-up pass that propagates widths up the tree to assign a minimum width and a preferred width to each element. By way of example, for a div element containing a paragraph of text, the minimum width may be the width as a line break placed after each word, and the preferred width may be the width without any line breaks.
• The second pass (i.e., the width calculation pass) may be a top-down pass that calculates the final width of each element. Depending on the style of the element, the final width may be derived from either its parent's width, or the minimum/preferred width.
• During the third pass (i.e., the block-formatting context flow pass), each element has a known width, and it its contents may be used to calculate its height. By way of example, for a div element containing a paragraph of text, after the width is determined, the text may be placed inside of it, and the height of each line may be summed to find the total height of the div. The direction of propagation may be complex. Elements whose contents are used to calculate its height may be referred to as block-formatting contexts (BFCs). Whether an element is a block-formatting context or not may be determined by its CSS style.
• The block-formatting context elements in the DOM tree may form a logical tree that may be overlaid onto the DOM. The block-formatting context overlay tree may be walked bottom-up, and by the time the browser system reaches the root of the DOM tree, it will have laid out the whole webpage. At the end of this phase, thebrowser system500 will be informed of the height of all elements, as well as their relative positions within the block-formatting context that contains them.
• The fourth pass (i.e., the absolute position calculation pass) may be a top down pass that uses the relative positions within each block-formatting context from the prior pass to calculate the absolute position of each element on the page.
• In an aspect, rendering may be achieved by walking the layout tree so that background elements are visited before foreground elements. Various aspects may draw each element into a graphics buffer in a manner consistent with its style, and display the contents of the buffer on the screen (e.g., via the GUI). These rendering operations may be computationally expensive because of the memory bandwidth used by the compositing steps. Various aspects may be configured to reduce the memory bandwidth required by each compositing step via parallelism or concurrent execution of the various components/subsystems.
• Generally, the performance of the layout and rendering operations are important due to their impact on everything from page load times to the responsiveness of the user interface. In addition, layout and rendering operations compete for CPU cycles with other important tasks, like executing JavaScript®.
• Along with sequential optimizations, various aspects may include both coarse and fine-grained parallelism to improve the performance of the layout and rendering engine. These two approaches may be complementary. At the coarse level, an aspect browser may move as much work as possible out of the critical path and into worker threads. At the fine level, the aspect browser may parallelize the layout and rendering algorithms/methods.
• In a conventional web browser, tasks that manipulate the DOM (e.g. parsing or JavaScript®) never execute at the same time as layout and rendering tasks, which ensures that the two do not interfere with each other. In contrast, various aspects overlap these two types of tasks. As such, in various aspects, the layout tree may not be updated every time the DOM changes.
• Various aspects may separate (or keep separate) the layout tree and the DOM. Updates to the layout tree may be performed as a batch operation at times when layout and rendering operations would normally occur; often this is after a parsing or JavaScript® execution task completes. Grouping the updates in this manner may mean that that thebrowser system500 may be required to maintain additional state information to identify portions of the DOM that have changed, but would avoid performing unnecessary work since the layout tree is not updated for each intermediate state of the DOM.
• Various aspects may update the layout tree when it is ready to do useful work with the results. The layout tree may be a separate entity from the DOM. All DOM changes may be performed without affecting the layout tree. Conversely therendering engine subsystem560 does not need to access the DOM in any way once the layout tree is updated. This enables parallelism, and also means that the layout tree must duplicate certain information that would conventionally be stored only in the DOM. In particular, the layout tree may contain direct references to text, images, CSS styles, and HTML canvas elements.
• Text and images may be immutable and shared with the DOM safely. CSS styles may be logically immutable, but the amount of data in a CSS style object may be too large (and/or they may be updated too frequently) to copy the entire object every time. Thus, in an aspect, each style object may be divided internally into many smaller sub-style objects. Shared sub-styles may be updated using a copy-on-write approach. Unshared sub-styles may be updated in place. Accordingly, copying a style object may only require creating a new style object that shares the same sub-styles, which may be much cheaper. In addition, the sub-styles may be grouped so that CSS properties that are updated together are in the same sub-style, which may minimize sub-style copies when updates occur. This arrangement allows the DOM, layout, and rendering components to reference the same CSS styles without changes made in one place/component being visible to the others. A similar copy-on-write approach may be used for HTML canvas elements.
• The separation of the layout tree from the DOM tree enables the coarse-grained parallelism in therendering engine subsystem560. When a web page is ready to be displayed for the first time to the user, thebrowser system500 may create a work item that initializes the layout tree and hands it off to therendering engine subsystem560 for processing. The separation of the layout and rendering operations into different threads allows the rest of thebrowser system500 to move forward, such as JavaScript® can be executed, user interface (UI) events can be processed, and CSS styling can be computed, etc.
• When therendering engine subsystem560 finishes its tasks and displays the page on the screen, it may submit a “LR work item,” to update the layout tree, and start the process all over again. Only the “LR work item” needs exclusive access to the DOM, and once the tree is updated, the other operations may be performed in parallel and/or asynchronously.
• Certain JavaScript® DOM APIs (e.g., getComputedStyle and offsetTop) may require information about the results that the layout algorithm computes. Therendering engine subsystem560 may be required to pause until the results are available. If therendering engine subsystem560 performs the layout in the main thread, it may duplicate computations being performed in the LR work item (or LR thread), which may waste time and energy.
• In an aspect, therendering engine subsystem560 may be configured to remember whether the layout tree has up-to-date layout information. If so, a synchronous layout request may be returned immediately. If not, the layout operations may be performed in the LR thread as normal, and therendering engine subsystem560 may be requested to notify the main thread when the layout process is complete. This delivers the needed results as quickly as possible while preventing duplicate work.
• In addition to parallelism, another advantage of separating the layout tree and the DOM is that therendering engine subsystem560 may be treated as a service shared between web pages. Since layout trees don't refer back to the DOM they were constructed from, the samerendering engine subsystem560 may manage all layout trees, regardless of their source. This means that expensive, finite rendering related resources like graphics buffers only need one instance in theentire browser system500.
• Yet another advantage provided by the layout tree is added flexibility in determining a user's intent when the user interacts with a page that is changing rapidly. For example, if a user clicks on a button that is being moved around the screen by JavaScript®, there is a delay between JavaScript® changing the DOM and the results appearing on the screen because layout and rendering operations take time. By the time the user's click is registered, the DOM may have been updated and the box's location from the browser's perspective may have changed. Even if the user's mouse pointer is directly over the box, the attempt to click may not be successful. However, because the layout tree is separate from the DOM, thebrowser system500 may have access to the current working tree and the last tree that was displayed on the screen. This enables thebrowser system500 to determine the object that the user intended to click on based upon what they saw when they clicked, and not the current state of the DOM, resulting in improved perceived responsiveness and a better user experience.
• The various aspects may be implemented on a variety of mobile computing devices, an example of which is illustrated inFIG. 12. Specifically,FIG. 12 is a system block diagram of a mobile transceiver device in the form of a smartphone/cell phone1200 suitable for use with any of the aspects. Thecell phone1200 may include aprocessor1201 coupled tointernal memory1202, adisplay1203, and to aspeaker1208. Additionally, thecell phone1200 may include anantenna1204 for sending and receiving electromagnetic radiation that may be connected to a wireless data link, cellular telephone transceiver, and/orwireless transceiver1205 coupled to theprocessor1201.Cell phones1200 typically also include menu selection buttons orrocker switches1206 for receiving user inputs.
• Atypical cell phone1200 also includes a sound encoding/decoding (CODEC)circuit1213 that digitizes sound received from a microphone into data packets suitable for wireless transmission and decodes received sound data packets to generate analog signals that are provided to thespeaker1208 to generate sound. Also, one or more of theprocessor1201,wireless transceiver1205 andCODEC circuit1213 may include a digital signal processor (DSP) circuit (not shown separately). Thecell phone1200 may further include a ZigBee® transceiver (i.e., an IEEE 802.15.4 transceiver)1213 for low-power short-range communications between wireless devices, or other similar communication circuitry (e.g., circuitry implementing the Bluetooth® or WiFi protocols, etc.).
• Various aspects may be implemented on any of a variety of commercially available server devices, such as theserver1300 illustrated inFIG. 13. Such aserver1300 typically includes a processor1301 coupled to volatile memory1302 and a large capacity nonvolatile memory, such as adisk drive1303. Theserver1300 may also include a floppy disc drive, compact disc (CD) orDVD disc drive1311 coupled to the processor1301. Theserver1300 may also include network access ports1306 coupled to the processor1301 for establishing data connections with anetwork1305, such as a local area network coupled to other communication system computers and servers.
• Other forms of computing devices may also benefit from the various aspects. Such computing devices typically include the components illustrated inFIG. 14 that illustrates an examplepersonal laptop computer1400. Such apersonal computer1400 generally includes aprocessor1401 coupled tovolatile memory1402 and a large capacity nonvolatile memory, such as adisk drive1403. Thecomputer1400 may also include a compact disc (CD) and/orDVD drive1404 coupled to theprocessor1401. Thecomputer device1400 may also include a number of connector ports coupled to theprocessor1401 for establishing data connections or receiving external memory devices, such as anetwork connection circuit1405 for coupling theprocessor1401 to a network. Thecomputer1400 may further be coupled to akeyboard1408, a pointing device such as amouse1410, and adisplay1409 as is well known in the computer arts.
• Theprocessors1201,1301,1401 may be any programmable microprocessor, microcomputer or multiple processor chip or chips that can be configured by software instructions (applications) to perform a variety of functions, including the functions of the various aspects described below. In some mobile devices, multiple processors1301 may be provided, such as one processor dedicated to wireless communication functions and one processor dedicated to running other applications. Typically, software applications may be stored in theinternal memory1202,1302,1303,1402 before they are accessed and loaded into theprocessor1201,1301,1401. Theprocessor1201,1301,1401 may include internal memory sufficient to store the application software instructions.
• The foregoing method descriptions and the process flow diagrams are provided merely as illustrative examples and are not intended to require or imply that the blocks of the various aspects must be performed in the order presented. As will be appreciated by one of skill in the art the order of blocks in the foregoing aspects may be performed in any order. Words such as “thereafter,” “then,” “next,” etc. are not intended to limit the order of the blocks; these words are simply used to guide the reader through the description of the methods. Further, any reference to claim elements in the singular, for example, using the articles “a,” “an” or “the” is not to be construed as limiting the element to the singular.
• The various illustrative logical blocks, modules, circuits, and algorithm blocks described in connection with the aspects disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and blocks have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
• The hardware used to implement the various illustrative logics, logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but, in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Alternatively, some blocks or methods may be performed by circuitry that is specific to a given function.
• In one or more exemplary aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a non-transitory computer-readable medium or non-transitory processor-readable medium. The steps of a method or algorithm disclosed herein may be embodied in a processor-executable software module, which may reside on a non-transitory computer-readable or processor-readable storage medium. Non-transitory computer-readable or processor-readable storage media may be any storage media that may be accessed by a computer or a processor. By way of example but not limitation, such non-transitory computer-readable or processor-readable media may include RAM, ROM, EEPROM, FLASH memory, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of non-transitory computer-readable and processor-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and/or instructions on a non-transitory processor-readable medium and/or computer-readable medium, which may be incorporated into a computer program product.
• The preceding description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein.

Claims (32)

What is claimed is:

1. A method of processing a webpage, comprising:

scanning an HTML document by a first process to discover external resources referenced in the HTML document, the first process executing in a processor of a computing device concurrent with an HTML parser process;

invoking by the first process a downloading of a resource document for a discovered external resource, the downloading being performed while the first process continues scanning the HTML document;

scanning the downloaded resource document by a second process to discover additional external resources, the second process scanning the downloaded resource document while the first process continues scanning the HTML document;

identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document;

receiving, by the second process, information pertaining to the attributes identified by the first process;

determining whether to initiate downloading of discovered additional resources by the second process based on the received information; and

rendering the HTML document on an electronic display of the computing device using the downloaded resources.

2. The method ofclaim 1, wherein:

scanning an HTML document by a first process comprises scanning the HTML document by an HTML document scanner process; and

scanning the downloaded resource document by a second process comprises scanning the downloaded resource document by a cascading style sheet document scanner process.

3. The method ofclaim 1, wherein determining whether to initiate downloading of discovered additional resources by the second process based on the received information comprises:

speculating regarding external resources required for rendering the HTML document on the electronic display of the computing device.

4. The method ofclaim 1, wherein scanning the downloaded resource document to discover additional external resources comprises:

scanning a style sheet document by the second process to discover additional external resources.

5. The method ofclaim 4, wherein:

identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document comprises identifying by the first process HTML id, class, and style attributes associated with HTML elements included the HTML document; and

receiving information pertaining to the attributes identified by the first process comprises receiving by the second process information pertaining to the identified HTML id, class, and style attributes associated with HTML elements included the HTML document.

6. The method ofclaim 5, wherein determining by the second process whether to download discovered additional resources based on the received information comprises:

determining whether every identified HTML id, class, and style attribute associated with a style rule has already been encountered by the first process;

immediately requesting resources referenced by the style rule in response to determining that every identified HTML id, class, and style attribute associated with the style rule has already been encountered by first process; and

storing the style rule in memory in response to determining that not every identified HTML id, class, and style attribute associated with the style rule has been encountered by first process.

7. The method ofclaim 6, further comprising:

generating a notification by the first process when scanning of the HTML document is complete; and

receiving the notification by the second process.

8. The method ofclaim 7, further comprising:

retrieving the stored style rule from memory by the second process in response to the second process receiving the notification;

determining whether every HTML id, class, and style attribute has already been encountered by the first process; and

requesting resources referenced by the retrieved style rule in response to determining that every HTML id, class, and style attribute has already been encountered by the first process.

9. A computing device, comprising:

means for scanning an HTML document by a first process to discover external resources referenced in the HTML document, the first process executing concurrent with an HTML parser process;

means for invoking by the first process a downloading of a resource document for a discovered external resource, the downloading being performed while the first process continues scanning the HTML document;

means for scanning the downloaded resource document by a second process to discover additional external resources, the second process scanning the downloaded resource document while the first process continues scanning the HTML document;

means for identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document;

means for receiving by the second process information pertaining to the attributes identified by the first process;

means for determining whether to initiate downloading of discovered additional resources by the second process based on the received information; and

means for rendering the HTML document on an electronic display of the computing device using the downloaded resources.

10. The computing device ofclaim 9, wherein:

means for scanning an HTML document by a first process comprises means for scanning the HTML document by an HTML document scanner process; and

means for scanning the downloaded resource document by a second process comprises means for scanning the downloaded resource document by a cascading style sheet document scanner process.

11. The computing device ofclaim 9, wherein means for determining whether to initiate downloading of discovered additional resources by the second process based on the received information comprises means for speculating regarding external resources required for rendering the HTML document on the electronic display.

12. The computing device ofclaim 9, wherein means for scanning the downloaded resource document to discover additional external resources comprises means for scanning a style sheet document by the second process to discover additional external resources.

13. The computing device ofclaim 12, wherein:

means for identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document comprises means for identifying by the first process HTML id, class, and style attributes associated with HTML elements included the HTML document; and

means for receiving information pertaining to the attributes identified by the first process comprises means for receiving by the second process information pertaining to the identified HTML id, class, and style attributes associated with HTML elements included the HTML document.

14. The computing device ofclaim 13, wherein means for determining by the second process whether to download discovered additional resources based on the received information comprises:

means for determining whether every identified HTML id, class, and style attribute associated with a style rule has already been encountered by first process;

means for immediately requesting resources referenced by the style rule in response to determining that every identified HTML id, class, and style attribute associated with the style rule has already been encountered by first process; and

means for storing the style rule in memory in response to determining that not every identified HTML id, class, and style attribute associated with the style rule has been encountered by first process.

15. The computing device ofclaim 14, further comprising:

means for generating a notification by the first process when scanning of the HTML document is complete; and

means for receiving the notification by the second process.

16. The computing device ofclaim 15, further comprising:

means for retrieving the stored style rule from memory by the second process in response to the second process receiving the notification;

means for determining whether every HTML id, class, and style attribute has already been encountered by the first process; and

means for requesting resources referenced by the retrieved style rule in response to determining that every HTML id, class, and style attribute has already been encountered by the first process.

17. A computing device, comprising:

a processor configured with processor-executable instructions to perform operations comprising:

scanning an HTML document by a first process to discover external resources referenced in the HTML document, the first process executing concurrent with an HTML parser process;

invoking by the first process a downloading of a resource document for a discovered external resource, the downloading being performed while the first process continues scanning the HTML document;

scanning the downloaded resource document by a second process to discover additional external resources, the second process scanning the downloaded resource document while the first process continues scanning the HTML document;

identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document;

receiving by the second process information pertaining to the attributes identified by the first process;

determining whether to initiate downloading of discovered additional resources by the second process based on the received information; and

rendering the HTML document on an electronic display of the computing device using the downloaded resources.

18. The computing device ofclaim 17, wherein the processor is configured with processor-executable instructions such that:

scanning an HTML document by a first process comprises scanning the HTML document by an HTML document scanner process; and

scanning the downloaded resource document by a second process comprises scanning the downloaded resource document by a cascading style sheet document scanner process.

19. The computing device ofclaim 17, wherein the processor is configured with processor-executable instructions such that determining whether to initiate downloading of discovered additional resources by the second process based on the received information comprises speculating regarding external resources required for rendering the HTML document on the electronic display of the computing device.

20. The computing device ofclaim 17, wherein the processor is configured with processor-executable instructions such that scanning the downloaded resource document to discover additional external resources comprises scanning a style sheet document by the second process to discover additional external resources.

21. The computing device ofclaim 20, wherein the processor is configured with processor-executable instructions such that:

identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document comprises identifying by the first process HTML id, class, and style attributes associated with HTML elements included the HTML document; and

receiving information pertaining to the attributes identified by the first process comprises receiving by the second process information pertaining to the identified HTML id, class, and style attributes associated with HTML elements included the HTML document.

22. The computing device ofclaim 21, wherein the processor is configured with processor-executable instructions such that determining by the second process whether to download discovered additional resources based on the received information comprises:

determining whether every identified HTML id, class, and style attribute associated with a style rule has already been encountered by first process;

immediately requesting resources referenced by the style rule in response to determining that every identified HTML id, class, and style attribute associated with the style rule has already been encountered by first process; and

storing the style rule in memory in response to determining that not every identified HTML id, class, and style attribute associated with the style rule has been encountered by first process.

23. The computing device ofclaim 22, wherein the processor is configured with processor-executable instructions to perform operations further comprising:

generating a notification by the first process when scanning of the HTML document is complete; and

receiving the notification by the second process.

24. The computing device ofclaim 23, wherein the processor is configured with processor-executable instructions to perform operations further comprising:

retrieving the stored style rule from memory by the second process in response to the second process receiving the notification;

determining whether every HTML id, class, and style attribute has already been encountered by the first process; and

requesting resources referenced by the retrieved style rule in response to determining that every HTML id, class, and style attribute has already been encountered by the first process.

25. A non-transitory computer readable storage medium having stored thereon processor-executable software instructions configured to cause a processor to perform operations for processing a webpage, the operations comprising:

scanning an HTML document by a first process to discover external resources referenced in the HTML document, the first process executing concurrent with an HTML parser process;

invoking by the first process a downloading of a resource document for a discovered external resource, the downloading being performed while the first process continues scanning the HTML document;

scanning the downloaded resource document by a second process to discover additional external resources, the second process scanning the downloaded resource document while the first process continues scanning the HTML document;

identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document;

receiving by the second process information pertaining to the attributes identified by the first process;

determining whether to initiate downloading of discovered additional resources by the second process based on the received information; and

rendering the HTML document on an electronic display of a computing device using the downloaded resources.

26. The non-transitory computer readable storage medium ofclaim 25, wherein the stored processor-executable software instructions are configured to cause a processor to perform operations such that:

scanning an HTML document by a first process comprises scanning the HTML document by an HTML document scanner process; and

scanning the downloaded resource document by a second process comprises scanning the downloaded resource document by a cascading style sheet document scanner process.

27. The non-transitory computer readable storage medium ofclaim 25, wherein the stored processor-executable software instructions are configured to cause a processor to perform operations such that determining whether to initiate downloading of discovered additional resources by the second process based on the received information comprises speculating regarding external resources required for rendering the HTML document on the electronic display of the computing device.

28. The non-transitory computer readable storage medium ofclaim 25, wherein the stored processor-executable software instructions are configured to cause a processor to perform operations such that scanning the downloaded resource document to discover additional external resources comprises scanning a style sheet document by the second process to discover additional external resources.

29. The non-transitory computer readable storage medium ofclaim 28, wherein the stored processor-executable software instructions are configured to cause a processor to perform operations such that:

identifying attributes of the HTML document by the first process while the second process continues scanning the downloaded resource document comprises identifying by the first process HTML id, class, and style attributes associated with HTML elements included the HTML document; and

receiving information pertaining to the attributes identified by the first process comprises receiving by the second process information pertaining to the identified HTML id, class, and style attributes associated with HTML elements included the HTML document.

30. The non-transitory computer readable storage medium ofclaim 29, wherein the stored processor-executable software instructions are configured to cause a processor to perform operations such that determining by the second process whether to download discovered additional resources based on the received information comprises:

determining whether every identified HTML id, class, and style attribute associated with a style rule has already been encountered by first process;

immediately requesting resources referenced by the style rule in response to determining that every identified HTML id, class, and style attribute associated with the style rule has already been encountered by first process; and

storing the style rule in memory in response to determining that not every identified HTML id, class, and style attribute associated with the style rule has been encountered by first process.

31. The non-transitory computer readable storage medium ofclaim 30, wherein the stored processor-executable software instructions are configured to cause a processor to perform operations comprising:

generating a notification by the first process when scanning of the HTML document is complete; and

receiving the notification by the second process.

32. The non-transitory computer readable storage medium ofclaim 31, wherein the stored processor-executable software instructions are configured to cause a processor to perform operations comprising:

retrieving the stored style rule from memory by the second process in response to the second process receiving the notification;

determining whether every HTML id, class, and style attribute has already been encountered by the first process; and

requesting resources referenced by the retrieved style rule in response to determining that every HTML id, class, and style attribute has already been encountered by the first process.

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