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

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Message-ID: <20140528165144.GK29957@tassilo.jf.intel.com>
Date:	Wed, 28 May 2014 09:51:44 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"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

> The only part I don't quite follow here is this:
>                       if (__test_and_set_bit(bit, (unsigned long *)&status))
>                                 continue;
> 
> Which seems to indicate the code is making sure each counter is
> processed only once. But it can only be processed once, if you have
> only one record. And if you have multiple, you want to be able to
> handle the same counter multiple times, at least once perf PEBS
> record. So I am a bit confused about this test.

Each PEBS record is only for a single counter overflow. So it
always should only be a single perf event.

-Andi
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