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Message-ID: <YvVtc8qY3/dS0r6J@kernel.org>
Date: Thu, 11 Aug 2022 17:58:27 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Jiri Olsa <jolsa@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
Ian Rogers <irogers@...gle.com>,
linux-perf-users@...r.kernel.org, Song Liu <songliubraving@...com>,
Hao Luo <haoluo@...gle.com>,
Blake Jones <blakejones@...gle.com>,
Milian Wolff <milian.wolff@...b.com>, bpf@...r.kernel.org
Subject: Re: [PATCH 0/4] Track processes properly for perf record --off-cpu
(v2)
Em Thu, Aug 11, 2022 at 11:54:52AM -0700, Namhyung Kim escreveu:
> Hello,
>
> This patch series implements inheritance of offcpu events for the
> child processes. Unlike perf events, BPF cannot know which task it
> should track except for ones set in a BPF map at the beginning. Add
> another BPF program to the fork path and add the process id to the map
> if the parent is tracked.
Thanks for resubmitting, applied!
Will be up in perf/core as soon as tests finish.
- Arnaldo
> Changes in v2)
> * drop already merged fixes
> * fix the shell test to omit noises
>
> With this change, it can get the correct off-cpu events for child
> processes. I've tested it with perf bench sched messaging which
> creates a lot of processes.
>
> $ sudo perf record -e dummy --off-cpu -- perf bench sched messaging
> # Running 'sched/messaging' benchmark:
> # 20 sender and receiver processes per group
> # 10 groups == 400 processes run
>
> Total time: 0.196 [sec]
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.178 MB perf.data (851 samples) ]
>
>
> $ sudo perf report --stat | grep -A1 offcpu
> offcpu-time stats:
> SAMPLE events: 851
>
> The benchmark passes messages by read/write and it creates off-cpu
> events. With 400 processes, we can see more than 800 events.
>
> The child process tracking is also enabled when -p option is given.
> But -t option does NOT as it only cares about the specific threads.
> It may be different what perf_event does now, but I think it makes
> more sense.
>
> You can get it from 'perf/offcpu-child-v2' branch in my tree
>
> https://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
>
> Thanks,
> Namhyung
>
>
> Namhyung Kim (4):
> perf offcpu: Check process id for the given workload
> perf offcpu: Parse process id separately
> perf offcpu: Track child processes
> perf offcpu: Update offcpu test for child process
>
> tools/perf/tests/shell/record_offcpu.sh | 57 ++++++++++++++++++++++---
> tools/perf/util/bpf_off_cpu.c | 53 ++++++++++++++++++++++-
> tools/perf/util/bpf_skel/off_cpu.bpf.c | 38 ++++++++++++++++-
> 3 files changed, 138 insertions(+), 10 deletions(-)
>
>
> base-commit: b39c9e1b101d2992de9981673919ae55a088792c
> --
> 2.37.1.595.g718a3a8f04-goog
--
- Arnaldo
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