Re: [PATCH v6 1/3] perf/core: use rb trees for pinned/flexible groups

[Peter Zijlstra]

On Thu, Aug 03, 2017 at 11:30:09PM +0300, Alexey Budankov wrote:
> On 03.08.2017 16:00, Peter Zijlstra wrote:
> > On Wed, Aug 02, 2017 at 11:13:54AM +0300, Alexey Budankov wrote:

> >> @@ -2759,13 +2932,13 @@ static void ctx_sched_out(struct 
> >> perf_event_context *ctx,
> >>  
> >>    perf_pmu_disable(ctx->pmu);
> >>    if (is_active & EVENT_PINNED) {
> >> -          list_for_each_entry(event, &ctx->pinned_groups, group_entry)
> >> -                  group_sched_out(event, cpuctx, ctx);
> >> +          perf_event_groups_iterate(&ctx->pinned_groups,
> >> +                          group_sched_out_callback, &params);
> > 
> > So here I would expect to not iterate events where event->cpu !=
> > smp_processor_id() (and ideally not where event->pmu != ctx->pmu).
> >
> 
> We still need to iterate thru all groups on thread context switch in 
> and out as well as iterate thru cpu == -1 list (software events) additionally 
> to smp_processor_id() list from multiplexing timer interrupt handler.

Well, just doing the @cpu=-1 and @cpu=this_cpu subtrees is less work
than iterating _everything_, right?

The rest will not survive event_filter_match() anyway, so iterating them
is complete waste of time, and once we have them in a tree, its actually
easy to find this subset.