Messages in this thread | | | From | Namhyung Kim <> | Subject | [PATCH 0/4] Track processes properly for perf record --off-cpu (v2) | Date | Thu, 11 Aug 2022 11:54:52 -0700 |
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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.
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
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