Date: Mon, 19 Jul 2010 12:04:33 -0300
From: Arnaldo Carvalho de Melo <acme@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: a.p.zijlstra@chello.nl, paulus@samba.org, mingo@elte.hu,
        linux-kernel@vger.kernel.org
Subject: Re: perf can't keep up with mmap data
Message-ID: <20100719150433.GB5222@ghostprotocols.net>
References: <20100719074813.GA418@lst.de>
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Em Mon, Jul 19, 2010 at 09:48:13AM +0200, Christoph Hellwig escreveu:
> When running current -tip perf in my 32-bit x86 kvm guest I get lots
> of messages like:
> 
> WARNING: failed to keep up with mmap data.
> 
> when starting perf top, and still quite a few everytime it refreshes the
> display.

Should be better reported, probably with a message suggesting to use:

perf top -r RTPRIO

or to reduce the sampling frequency:

perf top -F 500

to have:

   PerfTop: 287 irqs/sec  kernel:40.8%  exact:  0.0% [500Hz cycles], (all, 2 CPUs)

Instead of the default:

   PerfTop:  35 irqs/sec  kernel:25.7%  exact:  0.0% [1000Hz cycles], (all, 2 CPUs)

- Arnaldo
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