Messages in this thread | | | From | Namhyung Kim <> | Date | Fri, 6 Nov 2020 00:45:02 +0900 | Subject | Re: [RFC 1/2] perf/core: Enable sched_task callbacks if PMU has it |
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Hello,
On Thu, Nov 5, 2020 at 11:47 PM Liang, Kan <kan.liang@linux.intel.com> wrote: > > > > On 11/2/2020 9:52 AM, Namhyung Kim wrote: > > If an event associated with a PMU which has a sched_task callback, > > it should be called regardless of cpu/task context. For example, > > > I don't think it's necessary. We should call it when we have to. > Otherwise, it just waste cycles. > Shouldn't the patch 2 be enough?
I'm not sure, without this patch __perf_event_task_sched_in/out cannot be called for per-cpu events (w/o cgroups) IMHO. And I could not find any other place to check the perf_sched_cb_usages.
Thanks Namhyung
> > > a per-cpu event might enable large PEBS buffers so it needs to flush > > the buffer whenever task scheduling happens. > > > The underlying PMU may or may not require this for the given event, > > but it will be handled in the pmu::sched_task() callback anyway. > > > > Signed-off-by: Namhyung Kim <namhyung@kernel.org> > > --- > > kernel/events/core.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/kernel/events/core.c b/kernel/events/core.c > > index b458ed3dc81b..aaa0155c4142 100644 > > --- a/kernel/events/core.c > > +++ b/kernel/events/core.c > > @@ -4696,6 +4696,8 @@ static void unaccount_event(struct perf_event *event) > > dec = true; > > if (has_branch_stack(event)) > > dec = true; > > + if (event->pmu->sched_task) > > + dec = true; > > if (event->attr.ksymbol) > > atomic_dec(&nr_ksymbol_events); > > if (event->attr.bpf_event) > > @@ -11225,6 +11227,8 @@ static void account_event(struct perf_event *event) > > inc = true; > > if (is_cgroup_event(event)) > > inc = true; > > + if (event->pmu->sched_task) > > + inc = true; > > if (event->attr.ksymbol) > > atomic_inc(&nr_ksymbol_events); > > if (event->attr.bpf_event) > >
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