resource —- Resource usage information

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.

An OSError is raised on syscall failure.

  • exception resource.error
  • 一个被弃用的 OSError 的别名。

在 3.3 版更改: 根据 PEP 3151，这个类是 OSError 的别名。

Resource Limits

Resources usage can be limited using the setrlimit() 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 the getrlimit(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.

  • resource.RLIM_INFINITY

  • Constant used to represent the limit for an unlimited resource.

  • resource.getrlimit(resource)

  • Returns a tuple (soft, hard) with the current soft and hard limits ofresource. Raises ValueError if an invalid resource is specified, orerror if the underlying system call fails unexpectedly.

  • resource.setrlimit(resource, limits)

  • Sets new limits of consumption of resource. The limits 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.

Raises ValueError 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 of RLIM_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, but ValueErrorwill still be raised if the requested limit exceeds the system imposedlimit.

setrlimit may also raise error if the underlying system callfails.

VxWorks only supports setting RLIMIT_NOFILE.

  • resource.prlimit(pid, resource[, limits])
  • Combines setrlimit() and getrlimit() in one function andsupports to get and set the resources limits of an arbitrary process. Ifpid is 0, then the call applies to the current process. resource andlimits have the same meaning as in setrlimit(), except thatlimits is optional.

When limits is not given the function returns the resource limit of theprocess pid. When limits is given the resource limit of the process isset and the former resource limit is returned.

Raises ProcessLookupError when pid can't be found andPermissionError when the user doesn't have CAP_SYS_RESOURCE forthe process.

Availability: Linux 2.6.36 or later with glibc 2.13 or later.

3.4 新版功能.

These symbols define resources whose consumption can be controlled using thesetrlimit() and getrlimit() functions described below. The values ofthese symbols are exactly the constants used by C programs.

The Unix man page for getrlimit(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.

  • resource.RLIMIT_CORE

  • 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.

  • resource.RLIMIT_CPU

  • The maximum amount of processor time (in seconds) that a process can use. Ifthis limit is exceeded, a SIGXCPU signal is sent to the process. (Seethe signal module documentation for information about how to catch thissignal and do something useful, e.g. flush open files to disk.)

  • resource.RLIMIT_FSIZE

  • The maximum size of a file which the process may create.

  • resource.RLIMIT_DATA

  • The maximum size (in bytes) of the process's heap.

  • resource.RLIMIT_STACK

  • The maximum size (in bytes) of the call stack for the current process. This onlyaffects the stack of the main thread in a multi-threaded process.

  • resource.RLIMIT_RSS

  • The maximum resident set size that should be made available to the process.

  • resource.RLIMIT_NPROC

  • The maximum number of processes the current process may create.

  • resource.RLIMIT_NOFILE

  • The maximum number of open file descriptors for the current process.

  • resource.RLIMIT_OFILE

  • The BSD name for RLIMIT_NOFILE.

  • resource.RLIMIT_MEMLOCK

  • The maximum address space which may be locked in memory.

  • resource.RLIMIT_VMEM

  • The largest area of mapped memory which the process may occupy.

  • resource.RLIMIT_AS

  • The maximum area (in bytes) of address space which may be taken by the process.

  • resource.RLIMIT_MSGQUEUE

  • The number of bytes that can be allocated for POSIX message queues.

Availability: Linux 2.6.8 or later.

3.4 新版功能.

  • resource.RLIMIT_NICE
  • The ceiling for the process's nice level (calculated as 20 - rlim_cur).

Availability: Linux 2.6.12 or later.

3.4 新版功能.

  • resource.RLIMIT_RTPRIO
  • The ceiling of the real-time priority.

Availability: Linux 2.6.12 or later.

3.4 新版功能.

  • resource.RLIMIT_RTTIME
  • The time limit (in microseconds) on CPU time that a process can spendunder real-time scheduling without making a blocking syscall.

Availability: Linux 2.6.25 or later.

3.4 新版功能.

  • resource.RLIMIT_SIGPENDING
  • The number of signals which the process may queue.

Availability: Linux 2.6.8 or later.

3.4 新版功能.

  • resource.RLIMIT_SBSIZE
  • The maximum size (in bytes) of socket buffer usage for this user.This limits the amount of network memory, and hence the amount of mbufs,that this user may hold at any time.

Availability: FreeBSD 9 or later.

3.4 新版功能.

  • resource.RLIMIT_SWAP
  • The maximum size (in bytes) of the swap space that may be reserved orused by all of this user id's processes.This limit is enforced only if bit 1 of the vm.overcommit sysctl is set.Please see tuning(7)) for a complete description of this sysctl.

Availability: FreeBSD 9 or later.

3.4 新版功能.

  • resource.RLIMIT_NPTS
  • The maximum number of pseudo-terminals created by this user id.

Availability: FreeBSD 9 or later.

3.4 新版功能.

Resource Usage

These functions are used to retrieve resource usage information:

  • resource.getrusage(who)
  • This function returns an object that describes the resources consumed by eitherthe current process or its children, as specified by the who parameter. Thewho parameter should be specified using one of the RUSAGE_*constants described below.

A simple example:

  1. from resource import *
  2. import time
  3.  
  4. # a non CPU-bound task
  5. time.sleep(3)
  6. print(getrusage(RUSAGE_SELF))
  7.  
  8. # a CPU-bound task
  9. for i in range(10 ** 8):
  10.    _ = 1 + 1
  11. print(getrusage(RUSAGE_SELF))

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 fields ruutime and ru_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 the getrusage(2))_ man page fordetailed information about these values. A brief summary is presented here:

索引

域

Resource

0

ru_utime

time in user mode (float seconds)

1

ru_stime

time in system mode (float seconds)

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 a ValueError if an invalid who parameter isspecified. It may also raise error exception in unusual circumstances.

  • resource.getpagesize()
  • Returns the number of bytes in a system page. (This need not be the same as thehardware page size.)

The following RUSAGE_* symbols are passed to the getrusage()function to specify which processes information should be provided for.

  • resource.RUSAGE_SELF

  • Pass to getrusage() to request resources consumed by the callingprocess, which is the sum of resources used by all threads in the process.

  • resource.RUSAGE_CHILDREN

  • Pass to getrusage() to request resources consumed by child processesof the calling process which have been terminated and waited for.

  • resource.RUSAGE_BOTH

  • Pass to getrusage() to request resources consumed by both the currentprocess and child processes. May not be available on all systems.

  • resource.RUSAGE_THREAD

  • Pass to getrusage() to request resources consumed by the currentthread. May not be available on all systems.

3.2 新版功能.