Re: [PATCH 1/2] x86, perf: Remove warning for zero PEBS status

From: Peter Zijlstra
Date: Thu Dec 03 2015 - 16:28:42 EST


On Thu, Dec 03, 2015 at 01:22:19PM -0800, Andi Kleen wrote:
> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
>
> The recent change 75f80859b1 (... Robustify PEBS buffer drain)
> causes lots of warnings on different CPUs before Skylake
> when running PEBS intensive workloads.
>
> They can have a zero status field in the PEBS record when
> PEBS is racing with clearing of GLOBAl_STATUS.

Ah, so _that_ is the explanation! Please put that in a comment near that
code. This has long puzzled me.

Thanks for digging into that.
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