linux-kernel - Re: [RFC] x86, perf: high volume of events produces a flood of unknown NMIs

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Message-ID: <20110420191231.GB31724@redhat.com>
Date:	Wed, 20 Apr 2011 15:12:31 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, peterz@...radead.org,
	robert.richter@....com, andi@...stfloor.org, ming.m.lin@...el.com,
	eranian@...gle.com, ying.huang@...el.com,
	mathieu.desnoyers@...icios.com, acme@...hat.com
Subject: Re: [RFC] x86, perf: high volume of events produces a flood of
 unknown NMIs

On Wed, Apr 20, 2011 at 10:47:51PM +0400, Cyrill Gorcunov wrote:
> > Or perhaps we don't care about this because in the end perf can't even
> > capture the data without spitting out a CPU Overload message.
> > 
> > Thoughts?
> > 
> 
> Hi Don, just a thought -- since pmi masks lvtpc we could read it and check if it's
> masked or no, though I fear it is quite time consuming operation in compare with
> frames :( (hmm, intel spec mentions only p4 and xeon as masking lvtpc)

Been there, tried that.  It seems to be masked a large majority of the
time, even when the NMIs don't appear to be back-to-back.

Cheers,
Don
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