Messages in this thread | | | From | Song Liu <> | Subject | Re: [PATCH v8] perf: Sharing PMU counters across compatible events | Date | Wed, 11 Dec 2019 18:50:32 +0000 |
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Hi Peter and Jiri,
> On Dec 6, 2019, at 4:24 PM, Song Liu <songliubraving@fb.com> wrote: > > This patch tries to enable PMU sharing. When multiple perf_events are > counting the same metric, they can share the hardware PMU counter. We > call these events as "compatible events". > > The PMU sharing are limited to events within the same perf_event_context > (ctx). When a event is installed or enabled, search the ctx for compatible > events. This is implemented in perf_event_setup_dup(). One of these > compatible events are picked as the master (stored in event->dup_master). > Similarly, when the event is removed or disabled, perf_event_remove_dup() > is used to clean up sharing. > > A new state PERF_EVENT_STATE_ENABLED is introduced for the master event. > This state is used when the slave event is ACTIVE, but the master event > is not. > > On the critical paths (add, del read), sharing PMU counters doesn't > increase the complexity. Helper functions event_pmu_[add|del|read]() are > introduced to cover these cases. All these functions have O(1) time > complexity. > > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Arnaldo Carvalho de Melo <acme@redhat.com> > Cc: Jiri Olsa <jolsa@kernel.org> > Cc: Alexey Budankov <alexey.budankov@linux.intel.com> > Cc: Namhyung Kim <namhyung@kernel.org> > Cc: Tejun Heo <tj@kernel.org> > Signed-off-by: Song Liu <songliubraving@fb.com> > > --- > Changes in v8: > Fix issues with task event (Jiri). > Fix issues with event inherit. > Fix mmap'ed events, i.e. perf test 4 (kernel test bot). > > Changes in v7: > Major rewrite to avoid allocating extra master event.
Could you please share your feedbacks on this version?
Thanks, Song
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