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4b15226c14
Add module docstrings to counting.py, tracepoint.py, and twatch.py. This
satisfies pylint's missing-module-docstring check and prepares these
existing standalone scripts in tools/perf/python/ for the later commit
in this series ("perf script: Support standalone scripts and remove
embedded scripting"), which updates 'perf script -l' to scan
tools/perf/python/ and display each script's module docstring:
```
$ perf script -l
List of available scripts:
...
counting
Example for counting perf events.
...
tracepoint
Example showing how to enable a tracepoint and access its fields.
twatch
Example to show how to enable a software event and track
context switches.
...
```
Assisted-by: Antigravity:gemini-3.1-pro
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
61 lines
2.7 KiB
Python
Executable File
61 lines
2.7 KiB
Python
Executable File
#! /usr/bin/env python
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# SPDX-License-Identifier: GPL-2.0-only
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"""Example to show how to enable a software event and track context switches."""
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# -*- python -*-
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# -*- coding: utf-8 -*-
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# twatch - Experimental use of the perf python interface
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# Copyright (C) 2011 Arnaldo Carvalho de Melo <acme@redhat.com>
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#
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import perf
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def main(context_switch = 0, thread = -1):
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cpus = perf.cpu_map()
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threads = perf.thread_map(thread)
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evsel = perf.evsel(type = perf.TYPE_SOFTWARE,
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config = perf.COUNT_SW_DUMMY,
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task = 1, comm = 1, mmap = 0, freq = 0,
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wakeup_events = 1, watermark = 1,
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sample_id_all = 1, context_switch = context_switch,
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sample_type = perf.SAMPLE_PERIOD | perf.SAMPLE_TID | perf.SAMPLE_CPU)
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# What we want are just the PERF_RECORD_ lifetime events for threads,
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# using the default, PERF_TYPE_HARDWARE + PERF_COUNT_HW_CYCLES & freq=1
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# (the default), makes perf reenable irq_vectors:local_timer_entry, when
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# disabling nohz, not good for some use cases where all we want is to get
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# threads comes and goes... So use (perf.TYPE_SOFTWARE, perf_COUNT_SW_DUMMY,
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# freq=0) instead.
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evsel.open(cpus = cpus, threads = threads)
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evlist = perf.evlist(cpus, threads)
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evlist.add(evsel)
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evlist.mmap()
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while True:
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evlist.poll(timeout = -1)
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for cpu in cpus:
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event = evlist.read_on_cpu(cpu)
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if not event:
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continue
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print("cpu: {0}, pid: {1}, tid: {2} {3}".format(event.sample_cpu,
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event.sample_pid,
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event.sample_tid,
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event))
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if __name__ == '__main__':
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# To test the PERF_RECORD_SWITCH record, pick a pid and replace
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# in the following line.
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# Example output:
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# cpu: 3, pid: 31463, tid: 31593 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31593, switch_out: 1 }
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# cpu: 1, pid: 31463, tid: 31489 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31489, switch_out: 1 }
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# cpu: 2, pid: 31463, tid: 31496 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31496, switch_out: 1 }
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# cpu: 3, pid: 31463, tid: 31491 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31491, switch_out: 0 }
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#
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# It is possible as well to use event.misc & perf.PERF_RECORD_MISC_SWITCH_OUT
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# to figure out if this is a context switch in or out of the monitored threads.
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# If bored, please add command line option parsing support for these options :-)
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# # main(context_switch = 1, thread = 31463)
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main()
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