linux-kernel - Re: [RFC PATCH 5/7] perf, x86: use the PEBS auto reload mechanism when possible

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Date:	Wed, 28 May 2014 09:59:37 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Yan, Zheng" <zheng.z.yan@...el.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, eranian@...gle.com,
	ak@...ux.intel.com
Subject: Re: [RFC PATCH 5/7] perf, x86: use the PEBS auto reload mechanism
 when possible

On Wed, May 28, 2014 at 02:18:08PM +0800, Yan, Zheng wrote:
> When a fixed period is specified, this patch make perf use the PEBS
> auto reload mechanism. This makes normal profiling faster, because
> it avoids one costly MSR write in the PMI handler.
> 

You can't do this unconditionally. Like I think you mention in the next
patch, we need the PMI to fix up lots of cases.

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