linux-kernel - Re: [PATCH 6/8] perf: Account freq events per cpu

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Message-ID: <20130801133155.GB27162@twins.programming.kicks-ass.net>
Date:	Thu, 1 Aug 2013 15:31:55 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 6/8] perf: Account freq events per cpu

On Thu, Aug 01, 2013 at 02:46:58PM +0200, Jiri Olsa wrote:
> On Tue, Jul 23, 2013 at 02:31:04AM +0200, Frederic Weisbecker wrote:
> > This is going to be used by the full dynticks subsystem
> > as a finer-grained information to know when to keep and
> > when to stop the tick.
> > 
> > Original-patch-by: Peter Zijlstra <peterz@...radead.org>
> > Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> > Cc: Jiri Olsa <jolsa@...hat.com>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Namhyung Kim <namhyung@...nel.org>
> > Cc: Ingo Molnar <mingo@...nel.org>
> > Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> > Cc: Stephane Eranian <eranian@...gle.com>
> > ---
> >  kernel/events/core.c |    7 +++++++
> >  1 files changed, 7 insertions(+), 0 deletions(-)
> > 
> > diff --git a/kernel/events/core.c b/kernel/events/core.c
> > index b40c3db..f9bd39b 100644
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -141,6 +141,7 @@ enum event_type_t {
> >  struct static_key_deferred perf_sched_events __read_mostly;
> >  static DEFINE_PER_CPU(atomic_t, perf_cgroup_events);
> >  static DEFINE_PER_CPU(atomic_t, perf_branch_stack_events);
> > +static DEFINE_PER_CPU(atomic_t, perf_freq_events);
> >  
> >  static atomic_t nr_mmap_events __read_mostly;
> >  static atomic_t nr_comm_events __read_mostly;
> > @@ -3139,6 +3140,9 @@ static void unaccount_event_cpu(struct perf_event *event, int cpu)
> >  	}
> >  	if (is_cgroup_event(event))
> >  		atomic_dec(&per_cpu(perf_cgroup_events, cpu));
> > +
> > +	if (event->attr.freq)
> > +		atomic_dec(&per_cpu(perf_freq_events, cpu));
> >  }
> >  
> >  static void unaccount_event(struct perf_event *event)
> > @@ -6473,6 +6477,9 @@ static void account_event_cpu(struct perf_event *event, int cpu)
> >  	}
> >  	if (is_cgroup_event(event))
> >  		atomic_inc(&per_cpu(perf_cgroup_events, cpu));
> > +
> > +	if (event->attr.freq)
> > +		atomic_inc(&per_cpu(perf_freq_events, cpu));
> 
> cpu could be -1 in here.. getting:

Ho humm, right you are. 

So we have:

static void account_event_cpu(struct perf_event *event, int cpu)
{
	if (event->parent)
		return;

	if (has_branch_stack(event)) {
		if (!(event->attach_state & PERF_ATTACH_TASK))
			atomic_inc(&per_cpu(perf_branch_stack_events, cpu));
	}
	if (is_cgroup_event(event))
		atomic_inc(&per_cpu(perf_cgroup_events, cpu));

	if (event->attr.freq)
		atomic_inc(&per_cpu(perf_freq_events, cpu));
}

Where the freq thing is new and shiney, but we already had the other
two. Of those, cgroup events must be per cpu so that should be good,
the branch_stack thing tests ATTACH_TASK, which should also be good, but
leaves me wonder wth they do for those that are attached to tasks.

But yes, the frequency thing is borken.
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