From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jes Sorensen <Jes.Sorensen@redhat.com>
Subject: Re: Wiki docs on counting and tracing KVM perf events
Date: Thu, 20 May 2010 13:16:14 +0200
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Cc: Stefan Hajnoczi <stefanha@gmail.com>, kvm <kvm@vger.kernel.org>
To: Avi Kivity <avi@redhat.com>
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On 05/20/10 13:10, Avi Kivity wrote:
> On 05/20/2010 02:05 PM, Stefan Hajnoczi wrote:
>> Jes, you're right, something like "perf stat -e kvm:* --start" and
>> "perf stat --stop" would be more usable for system-wide monitoring.  I
>> wonder if it is possible to support this or whether the perf process
>> needs to periodically accumulate the counters (i.e. babysit the kernel
>> infrastructure)?
>>    
> 
> perf needs to be running to pull data out of the kernel (and since
> profiling is tied to an fd life cycle).
> 
> What's wrong with starting perf after the warm-up period and stopping it
> before it's done?

It's pretty hard to script.

I have scripts that do 'read_stats() ; run_test() ; read_stats() ;
calc_average()'

Autotest would like to do this kinda stuff too.

Jes