linux-kernel - Re: [RFC PATCH 6/7] perf, x86: large PEBS interrupt threshold

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Message-ID: <20140528174545.GN29957@tassilo.jf.intel.com>
Date:	Wed, 28 May 2014 10:45:45 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Stephane Eranian <eranian@...gle.com>,
	"Yan, Zheng" <zheng.z.yan@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>
Subject: Re: [RFC PATCH 6/7] perf, x86: large PEBS interrupt threshold

> So the window is fairly large for another to slip in, esp if you have a
> fast (say inst-ret) and a slow (say br-misp) event.

yes, but unless you have really small periods it's still very unlikely
that they synchronize, so it will only happen very rarely.  And the
rare cases won't affect the statistics very much.

Even with multi-pebs the min period is 1000, which is several
orders of magnitude larger than the typical window.

-Andi
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