linux-kernel - Re: [patch] x86, perf: avoid spamming kernel log for bts buffer failure

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Message-ID: <20140702145411.GI19379@twins.programming.kicks-ass.net>
Date:	Wed, 2 Jul 2014 16:54:11 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	David Rientjes <rientjes@...gle.com>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch] x86, perf: avoid spamming kernel log for bts buffer
 failure

On Wed, Jul 02, 2014 at 03:38:50PM +0200, Stephane Eranian wrote:
> On Wed, Jul 2, 2014 at 3:31 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> > Right, that'd suck. I suppose we could also change that to allocate the
> > DS resources on first demand and never free them again.
> >
> Some may argue that if you never use perf_event again, you are wasting
> (1 + 1 + 4) pages per CPU. That may not be okay on some systems.
> 
> But yes, it would avoid this problem and also take the penalty for the allocs
> only once.

We could of course over engineer this and put a timer on them to free
after 5 minutes to avoid the alloc/free cycle for workloads that
create/destroy events a lot.

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