linux-kernel - Re: [Stable-review] [28/29] perf events: Dont report side-band events on each cpu for per-task-per-cpu events

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Date:	Sat, 23 Jan 2010 07:33:46 -0800
From:	Greg KH <gregkh@...e.de>
To:	Stefan Bader <stefan.bader@...onical.com>
Cc:	linux-kernel@...r.kernel.org, stable@...nel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	stable-review@...nel.org, alan@...rguk.ukuu.org.uk
Subject: Re: [Stable-review] [28/29] perf events: Dont report side-band
	events on each cpu for per-task-per-cpu events

On Sat, Jan 23, 2010 at 12:38:41PM +0100, Stefan Bader wrote:
> Greg KH wrote:
> > 2.6.32-stable review patch.  If anyone has any objections, please let us know.
> > 
> > ------------------
> > 
> > From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > 
> > commit 5d27c23df09b702868d9a3bff86ec6abd22963ac upstream.
> > 
> > Acme noticed that his FORK/MMAP numbers were inflated by about
> > the same factor as his cpu-count.
> > 
> > This led to the discovery of a few more sites that need to
> > respect the event->cpu filter.
> > 
> > Reported-by: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
> > Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > Cc: Paul Mackerras <paulus@...ba.org>
> > LKML-Reference: <20091217121830.215333434@...llo.nl>
> > Signed-off-by: Ingo Molnar <mingo@...e.hu>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
> > 
> > ---
> >  kernel/perf_event.c |   20 ++++++++++++++++++--
> >  1 file changed, 18 insertions(+), 2 deletions(-)
> > 
> > --- a/kernel/perf_event.c
> > +++ b/kernel/perf_event.c
> > @@ -1359,6 +1359,9 @@ static void perf_ctx_adjust_freq(struct 
> >  		if (event->state != PERF_EVENT_STATE_ACTIVE)
> >  			continue;
> >  
> > +		if (event->cpu != -1 && event->cpu != smp_processor_id())
> > +			continue;
> > +
> >  		hwc = &event->hw;
> >  
> >  		interrupts = hwc->interrupts;
> > @@ -3226,6 +3229,9 @@ static void perf_event_task_output(struc
> >  
> >  static int perf_event_task_match(struct perf_event *event)
> >  {
> > +	if (event->cpu != -1 && event->cpu != smp_processor_id())
> > +		return 0;
> > +
> >  	if (event->attr.comm || event->attr.mmap || event->attr.task)
> >  		return 1;
> >  
> 
> > @@ -3262,6 +3268,7 @@ static void perf_event_task_event(struct
> >  		ctx = rcu_dereference(task_event->task->perf_event_ctxp);
> >  	if (ctx)
> >  		perf_event_task_ctx(ctx, task_event);
> > +	put_cpu_var(perf_cpu_context);
> >  	rcu_read_unlock();
> >  }
> 
> I believe this hunk drops the move of put_cpu_var. The upstream hunk looks like
> this:
> 
> @ -3290,12 +3296,11 @@ static void perf_event_task_event(struct perf_task_event
>         rcu_read_lock();
>         cpuctx = &get_cpu_var(perf_cpu_context);
>         perf_event_task_ctx(&cpuctx->ctx, task_event);
> -       put_cpu_var(perf_cpu_context);
> -
>         if (!ctx)
>                 ctx = rcu_dereference(task_event->task->perf_event_ctxp);
>         if (ctx)
>                 perf_event_task_ctx(ctx, task_event);
> +       put_cpu_var(perf_cpu_context);
>         rcu_read_unlock();
>  }

Good catch, thanks, I merged this by hand (it was needed by the patch
after this), and I missed this chunk.

thanks,

greg k-h
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