linux-kernel - Re: [PATCH 7/7] perf, x86: Implement 64 bit counter support for IBS

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Message-ID: <20110801055540.GA4590@erda.amd.com>
Date:	Mon, 1 Aug 2011 07:55:40 +0200
From:	Robert Richter <robert.richter@....com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/7] perf, x86: Implement 64 bit counter support for IBS

On 29.07.11 13:02:42, Peter Zijlstra wrote:
> On Fri, 2011-07-29 at 18:58 +0200, Peter Zijlstra wrote:
> > On Thu, 2011-07-28 at 15:46 +0200, Robert Richter wrote:
> > > This patch implements 64 bit counter support for IBS. The sampling
> > > period is no longer limited to the hw counter width.
> > 
> > That should never be the case, even for shorter hw counter, in such a
> > case you should ignore overflows until you reach the programmed period.
> 
> Hmm, I might have mis-understood, is that exactly what this patch
> implements, or does this patch add support for new hardware?

Yes, this patch implements 64 bit counter in software and doesn't add
a new hardware feature. It implements 64 bit counting by throwing away
interrupts if the period isn't reached.

-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center

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