linux-kernel - Re: [PATCH] perf, x86: Add workaround for MEM_*

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Message-ID: <m261z3uipb.fsf@firstfloor.org>
Date:	Wed, 01 May 2013 02:56:32 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...e.hu, eranian@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf, x86: Add workaround for MEM_*_RETIRED errata BV98

Peter Zijlstra <peterz@...radead.org> writes:
>
> So you're saying that if two SMT siblings count the same MEM_*_RETIRED event
> (on the same counter?) events can get accounted to the wrong sibling?

It can happen regardless of what event is enabled on the other counter.

> And when the other sibling doesn't have (the same counter?) enabled we
> can loose events?

doesn't have any events enabled.

> This begs the question what happens when the sibling does have the (same?)
> counter enabled but counting an all together different event; do we then still
> 'loose' events from the one sibling and add then to the other counter?

Yes, that is what the patch fixes.

Of course only if you actually apply it, and not lose it as usual.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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