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BCC - Tools for BPF-based Linux IO analysis, networking, monitoring, and more

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iovisor/bcc

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BPF Compiler Collection (BCC)

BCC is a toolkit for creating efficient kernel tracing and manipulationprograms, and includes several useful tools and examples. It makes use ofextended BPF (Berkeley Packet Filters), formally known as eBPF, a new featurethat was first added to Linux 3.15. Much of what BCC uses requires Linux 4.1and above.

eBPF wasdescribed by Ingo Molnár as:

One of the more interesting features in this cycle is the ability to attach eBPF programs (user-defined, sandboxed bytecode executed by the kernel) to kprobes. This allows user-defined instrumentation on a live kernel image that can never crash, hang or interfere with the kernel negatively.

BCC makes BPF programs easier to write, with kernel instrumentation in C(and includes a C wrapper around LLVM), and front-ends in Python and lua.It is suited for many tasks, including performance analysis and networktraffic control.

Screenshot

This example traces a disk I/O kernel function, and populates an in-kernelpower-of-2 histogram of the I/O size. For efficiency, only the histogramsummary is returned to user-level.

# ./bitehist.pyTracing... Hit Ctrl-C to end.^C     kbytes: count     distribution       0 -> 1: 3||       2 -> 3: 0||       4 -> 7: 211|**********|       8 -> 15: 0||      16 -> 31: 0||      32 -> 63: 0||      64 -> 127: 1||     128 -> 255: 800|**************************************|

The above output shows a bimodal distribution, where the largest mode of800 I/O was between 128 and 255 Kbytes in size.

See the source:bitehist.py. What this traces,what this stores, and how the data is presented, can be entirely customized.This shows only some of many possible capabilities.

Installing

SeeINSTALL.md for installation steps on your platform.

FAQ

SeeFAQ.txt for the most common troubleshoot questions.

Reference guide

Seedocs/reference_guide.md for the reference guide to the bcc and bcc/BPF APIs.

Contents

Some of these are single files that contain both C and Python, others have apair of .c and .py files, and some are directories of files.

Tracing

Examples

Tools

Memory and Process Tools
Performance and Time Tools
CPU and Scheduler Tools
Network and Sockets Tools
Storage and Filesystems Tools
Filesystems Tools

Networking

Examples:

BPF Introspection

Tools that help to introspect BPF programs.

  • introspection/bps.c: List all BPF programs loaded into the kernel. 'ps' for BPF programs.Examples.

Motivation

BPF guarantees that the programs loaded into the kernel cannot crash, andcannot run forever, but yet BPF is general purpose enough to perform manyarbitrary types of computation. Currently, it is possible to write a program inC that will compile into a valid BPF program, yet it is vastly easier towrite a C program that will compile into invalid BPF (C is like that). The userwon't know until trying to run the program whether it was valid or not.

With a BPF-specific frontend, one should be able to write in a language andreceive feedback from the compiler on the validity as it pertains to a BPFbackend. This toolkit aims to provide a frontend that can only create valid BPFprograms while still harnessing its full flexibility.

Furthermore, current integrations with BPF have a kludgy workflow, sometimesinvolving compiling directly in a linux kernel source tree. This toolchain aimsto minimize the time that a developer spends getting BPF compiled, and insteadfocus on the applications that can be written and the problems that can besolved with BPF.

The features of this toolkit include:

  • End-to-end BPF workflow in a shared library
    • A modified C language for BPF backends
    • Integration with llvm-bpf backend for JIT
    • Dynamic (un)loading of JITed programs
    • Support for BPF kernel hooks: socket filters, tc classifiers,tc actions, and kprobes
  • Bindings for Python
  • Examples for socket filters, tc classifiers, and kprobes
  • Self-contained tools for tracing a running system

In the future, more bindings besides python will likely be supported. Feel freeto add support for the language of your choice and send a pull request!

Tutorials

Networking

At Red Hat Summit 2015, BCC was presented as part of asession on BPF.A multi-host vxlan environment is simulated and a BPF program used to monitorone of the physical interfaces. The BPF program keeps statistics on the innerand outer IP addresses traversing the interface, and the userspace componentturns those statistics into a graph showing the traffic distribution atmultiple granularities. See the codehere.

Contributing

Already pumped up to commit some code? Here are some resources to join thediscussions in theIOVisor community and seewhat you want to work on.

External links

Looking for more information on BCC and how it's being used? You can find links to other BCC content on the web inLINKS.md.

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