linux-kernel - Re: [RFC][PATCH 3/9] perf: export registerred pmus via sysfs

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Message-ID: <1273592789.1810.41.camel@laptop>
Date:	Tue, 11 May 2010 17:46:29 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Borislav Petkov <bp@...64.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Lin Ming <ming.m.lin@...el.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"eranian@...il.com" <eranian@...il.com>,
	"Gary.Mohr@...l.com" <Gary.Mohr@...l.com>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Paul Mackerras <paulus@...ba.org>,
	"David S. Miller" <davem@...emloft.net>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Paul Mundt <lethal@...ux-sh.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [RFC][PATCH 3/9] perf: export registerred pmus via sysfs

On Tue, 2010-05-11 at 17:37 +0200, Borislav Petkov wrote:
> From: Peter Zijlstra <peterz@...radead.org>
> Date: Tue, May 11, 2010 at 10:25:15AM -0400
> 
> > On Tue, 2010-05-11 at 16:15 +0200, Borislav Petkov wrote:
> > > Another point I have is that MCEs don't need pmus so we should consider
> > > having the ability to decouple events from pmus.
> > 
> > Strictly speaking tracepoints are software events, which run off of a
> > software 'pmu'. So no, we can't decouple, they need a 'pmu' context.
> 
> We could make this configurable depending on the severity of the error.
> I'm guessing for further event handling through the perf infrastructure
> we cannot run without a sw pmu context but on critical conditions
> we need to run as fast and as sparingly as possible so I'm thinking
> maybe adding some specially tailored callbacks to the MCE tracepoint
> trace_mce_record, as Steven suggested.

Well, all the tracepoint stuff should already be NMI-safe (all of perf
events needs to be because the PMI is an NMI) and I think perf as a
whole would like to run as fast as possible, so I don't yet see the need
for special purpose hooks (which I'll try to resist as much as
possible).



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