This module provides basic mechanisms for measuring and controlling systemresources utilized by a program.
Symbolic constants are used to specify particular system resources and torequest usage information about either the current process or its children.
AnOSError is raised on syscall failure.
Resources usage can be limited using thesetrlimit() function describedbelow. Each resource is controlled by a pair of limits: a soft limit and a hardlimit. The soft limit is the current limit, and may be lowered or raised by aprocess over time. The soft limit can never exceed the hard limit. The hardlimit can be lowered to any value greater than the soft limit, but not raised.(Only processes with the effective UID of the super-user can raise a hardlimit.)
The specific resources that can be limited are system dependent. They aredescribed in thegetrlimit(2) man page. The resources listed beloware supported when the underlying operating system supports them; resourceswhich cannot be checked or controlled by the operating system are not defined inthis module for those platforms.
Constant used to represent the the limit for an unlimited resource.
Returns a tuple(soft,hard) with the current soft and hard limits ofresource. RaisesValueError if an invalid resource is specified, orerror if the underlying system call fails unexpectedly.
Sets new limits of consumption ofresource. Thelimits argument must be atuple(soft,hard) of two integers describing the new limits. A value ofRLIM_INFINITY can be used to request a limit that isunlimited.
RaisesValueError if an invalid resource is specified, if the new softlimit exceeds the hard limit, or if a process tries to raise its hard limit.Specifying a limit ofRLIM_INFINITY when the hard orsystem limit for that resource is not unlimited will result in aValueError. A process with the effective UID of super-user canrequest any valid limit value, including unlimited, butValueErrorwill still be raised if the requested limit exceeds the system imposedlimit.
setrlimit may also raiseerror if the underlying system callfails.
These symbols define resources whose consumption can be controlled using thesetrlimit() andgetrlimit() functions described below. The values ofthese symbols are exactly the constants used by C programs.
The Unix man page forgetrlimit(2) lists the available resources.Note that not all systems use the same symbol or same value to denote the sameresource. This module does not attempt to mask platform differences — symbolsnot defined for a platform will not be available from this module on thatplatform.
The maximum size (in bytes) of a core file that the current process can create.This may result in the creation of a partial core file if a larger core would berequired to contain the entire process image.
The maximum amount of processor time (in seconds) that a process can use. Ifthis limit is exceeded, aSIGXCPU signal is sent to the process. (Seethesignal module documentation for information about how to catch thissignal and do something useful, e.g. flush open files to disk.)
The maximum size of a file which the process may create. This only affects thestack of the main thread in a multi-threaded process.
The maximum size (in bytes) of the process’s heap.
The maximum size (in bytes) of the call stack for the current process.
The maximum resident set size that should be made available to the process.
The maximum number of processes the current process may create.
The maximum number of open file descriptors for the current process.
The BSD name forRLIMIT_NOFILE.
The maximum address space which may be locked in memory.
The largest area of mapped memory which the process may occupy.
The maximum area (in bytes) of address space which may be taken by the process.
These functions are used to retrieve resource usage information:
This function returns an object that describes the resources consumed by eitherthe current process or its children, as specified by thewho parameter. Thewho parameter should be specified using one of theRUSAGE_*constants described below.
The fields of the return value each describe how a particular system resourcehas been used, e.g. amount of time spent running is user mode or number of timesthe process was swapped out of main memory. Some values are dependent on theclock tick internal, e.g. the amount of memory the process is using.
For backward compatibility, the return value is also accessible as a tuple of 16elements.
The fieldsru_utime andru_stime of the return value arefloating point values representing the amount of time spent executing in usermode and the amount of time spent executing in system mode, respectively. Theremaining values are integers. Consult thegetrusage(2) man page fordetailed information about these values. A brief summary is presented here:
| Index | Field | Resource |
|---|---|---|
| 0 | ru_utime | time in user mode (float) |
| 1 | ru_stime | time in system mode (float) |
| 2 | ru_maxrss | maximum resident set size |
| 3 | ru_ixrss | shared memory size |
| 4 | ru_idrss | unshared memory size |
| 5 | ru_isrss | unshared stack size |
| 6 | ru_minflt | page faults not requiring I/O |
| 7 | ru_majflt | page faults requiring I/O |
| 8 | ru_nswap | number of swap outs |
| 9 | ru_inblock | block input operations |
| 10 | ru_oublock | block output operations |
| 11 | ru_msgsnd | messages sent |
| 12 | ru_msgrcv | messages received |
| 13 | ru_nsignals | signals received |
| 14 | ru_nvcsw | voluntary context switches |
| 15 | ru_nivcsw | involuntary context switches |
This function will raise aValueError if an invalidwho parameter isspecified. It may also raiseerror exception in unusual circumstances.
Returns the number of bytes in a system page. (This need not be the same as thehardware page size.) This function is useful for determining the number of bytesof memory a process is using. The third element of the tuple returned bygetrusage() describes memory usage in pages; multiplying by page sizeproduces number of bytes.
The followingRUSAGE_* symbols are passed to thegetrusage()function to specify which processes information should be provided for.
Pass togetrusage() to request resources consumed by the callingprocess, which is the sum of resources used by all threads in the process.
Pass togetrusage() to request resources consumed by child processesof the calling process which have been terminated and waited for.
Pass togetrusage() to request resources consumed by both the currentprocess and child processes. May not be available on all systems.
Pass togetrusage() to request resources consumed by the currentthread. May not be available on all systems.
New in version 3.2.
34.10.pipes — Interface to shell pipelines
34.12.nis — Interface to Sun’s NIS (Yellow Pages)
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