linux-kernel - Re: [PATCH] perf: remove sw events from multiplexing rotation list

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Message-ID: <1346947316.18408.36.camel@twins>
Date:	Thu, 06 Sep 2012 18:01:56 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, fweisbec@...il.com
Subject: Re: [PATCH] perf: remove sw events from multiplexing rotation list

On Thu, 2012-09-06 at 15:23 +0200, Stephane Eranian wrote:
> Software events (sw,tracepoints,...) do not need to be
> multiplexed. However, when using a SW event, the SW PMU
> (TYPE_SOFTWARE, TYPE_TRACEPOINT) was added to the per-cpu
> rotation_list. That list is used by perf_rotate_context()
> to iterate over all the PMUs to rotate event lists and
> multiplex.
> 
> This is not needed for SW events. Doing this adds some
> unnecessary overhead, so drop it by rejecting SW PMUs
> in perf_pmu_rotate_start().

Thanks!
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