linux-kernel - Re: [PATCH 1/3] perf, x86: Blacklist all MEM_*

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Message-ID: <20130515165152.GB13916@laptop.home>
Date:	Wed, 15 May 2013 18:51:52 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Andi Kleen <ak@...ux.intel.com>, Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] perf, x86: Blacklist all MEM_*_RETIRED events for IVB

On Wed, May 15, 2013 at 04:20:46PM +0200, Stephane Eranian wrote:
> Hi,
> 
> Based on our testing, it appears the corruption occurs only
> when the MEM_* events are used and only on the sibling
> counter. In other words, if HT0 has MEM_* in cntr0, then
> HT1 cntr0 cannot be used, otherwise whatever is there may
> get corrupted.

Ah, great. That is the least horrid case :-)

> So I think we could enhance Andi's initial patch
> to handle this case instead of blacklist those events. They are
> very important events.

Will you take a stab at it? I suppose you'll have to make each counter
have a shared resource and have the mem_*_retired events mark the
resource taken.

Also, did you test what happens when you turn SMT off in the BIOS so you
get double the amount of counters; do we then leak into CNTn+4 or is all
well again?


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