linux-kernel - Re: perf: odd event scheduling issue

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Date:	Wed, 20 May 2015 17:25:34 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: perf: odd event scheduling issue

On Wed, May 20, 2015 at 03:52:09PM +0200, Peter Zijlstra wrote:
> >     
> >     This patch limits the number of counters available to each CPU when
> >     the HT bug workaround is enabled.
> >     
> >     This is necessary to avoid situation of counter starvation. Such can
> >     arise from configuration where one HT thread, HT0, is using all 4 counters
> >     with corrupting events which require exclusion the the sibling HT, HT1.
> >     

> 
> OK, so if you have the watchdog enabled, that's 1 event, and having a
> max of 2 GP events, adding another 2 events is fail.

Hmm, so we count all events, including those scheduled on fixed purpose
counters.

Lemme see if I can cure that.
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