linux-kernel - Re: [PATCH V8 3/8] perf, x86: handle multiple records in PEBS buffer

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Message-ID: <20150508110547.GS2366@two.firstfloor.org>
Date:	Fri, 8 May 2015 13:05:47 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Kan Liang <kan.liang@...el.com>
Cc:	peterz@...radead.org, mingo@...nel.org, acme@...radead.org,
	eranian@...gle.com, andi@...stfloor.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V8 3/8] perf, x86: handle multiple records in PEBS buffer

> The first issue is that the 'status' field of the PEBS record is a copy
> of the GLOBAL_STATUS MSR at PEBS assist time. To see why this is a

I wanted to mention that Skylake has this issue fixed. The status
field in PEBS is now only the counter that triggered the PEBS record.

> The second issue is that the hardware will only emit one record for two
> or more counters if the event that triggers the assist is 'close'. The

If two events gets merged it is one or the other.

-Andi
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