Messages in this thread | | | From | Song Liu <> | Subject | Re: [PATCH 1/2] perf/core: Share an event with multiple cgroups | Date | Tue, 30 Mar 2021 06:33:16 +0000 |
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> On Mar 29, 2021, at 4:33 AM, Namhyung Kim <namhyung@kernel.org> wrote: > > On Mon, Mar 29, 2021 at 2:17 AM Song Liu <songliubraving@fb.com> wrote: >>> On Mar 23, 2021, at 9:21 AM, Namhyung Kim <namhyung@kernel.org> wrote: >>> >>> As we can run many jobs (in container) on a big machine, we want to >>> measure each job's performance during the run. To do that, the >>> perf_event can be associated to a cgroup to measure it only. >>>
[...]
>>> + return 0; >>> +} >> >> Could you please explain why we need this logic in can_attach? > > IIUC the ss->attach() is called after a task's cgroup membership > is changed. But we want to collect the performance numbers for > the old cgroup just before the change. As the logic merely checks > the current task's cgroup, it should be done in the can_attach() > which is called before the cgroup change.
Thanks for the explanations.
Overall, I really like the core idea, especially that the overhead on context switch is bounded (by the depth of cgroup tree).
Is it possible to make PERF_EVENT_IOC_ATTACH_CGROUP more flexible? Specifically, if we can have
PERF_EVENT_IOC_ADD_CGROUP add a cgroup to the list PERF_EVENT_IOC_EL_CGROUP delete a cgroup from the list
we can probably share these events among multiple processes, and these processes don't need to know others' cgroup list. I think this will be useful for users to build customized monitoring in its own container.
Does this make sense?
Thanks, Song
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