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
