linux-kernel - Re: [PATCH v2] perfcounters: record time running and time enabled for each counter

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Message-ID: <20090321155442.GB6356@elte.hu>
Date:	Sat, 21 Mar 2009 16:54:42 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] perfcounters: record time running and time enabled
	for each counter


* Andrew Morton <akpm@...ux-foundation.org> wrote:

> > @@ -243,6 +259,8 @@ struct perf_counter {
> >  
> >  	struct perf_counter		*parent;
> >  	struct list_head		child_list;
> > +	atomic64_t			child_time_enabled;
> > +	atomic64_t			child_time_running;
> 
> These read like booleans, but why are they atomic64_t's?

for inherited counters these values get collected back into a 
'parent counter' in a lockless way - hence to not lose statistics on 
SMP they need to be atomic64_t.

> > @@ -290,6 +308,8 @@ struct perf_counter_context {
> >  	int			nr_active;
> >  	int			is_active;
> >  	struct task_struct	*task;
> > +	u64			time_now;
> > +	u64			time_lost;
> >  #endif
> >  };
> 
> I don't have a copy of this header file handy, but from the 
> snippet I see here, it doesn't look as though it is as clear and 
> as understadable as we can possibly make it?

i'll post the latest perfcounters tree - it's time for that anyway.

	Ingo
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