linux-kernel - Re: [PATCH 15/34] perf, core: Add a concept of a weightened sample

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Message-ID: <20121023131901.GU16230@one.firstfloor.org>
Date:	Tue, 23 Oct 2012 15:19:01 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org, acme@...hat.com, eranian@...gle.com,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 15/34] perf, core: Add a concept of a weightened sample

On Tue, Oct 23, 2012 at 03:13:52PM +0200, Peter Zijlstra wrote:
> > @@ -562,6 +565,7 @@ enum perf_event_type {
> >          *      { u64                   stream_id;} && PERF_SAMPLE_STREAM_ID
> >          *      { u32                   cpu, res; } && PERF_SAMPLE_CPU
> >          *      { u64                   period;   } && PERF_SAMPLE_PERIOD
> > +        *      { u64                   weight;   } && PERF_SAMPLE_WEIGHT
> >          *
> >          *      { struct read_format    values;   } && PERF_SAMPLE_READ
> >          * 
> 
> So the only issues I have are that his makes every sample more expensive
> by having to 0 out that weight data and the sample placement.

It's only reported when explicitely enabled (-W). So most users
shouldn't see any overhead (except two untaken if()s or so)

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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