From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: Wiki docs on counting and tracing KVM perf events
Date: Thu, 20 May 2010 15:14:52 +0300
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Cc: Jes Sorensen <Jes.Sorensen@redhat.com>, kvm <kvm@vger.kernel.org>
To: Stefan Hajnoczi <stefanha@gmail.com>
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On 05/20/2010 02:23 PM, Stefan Hajnoczi wrote:
> On Thu, May 20, 2010 at 12:16 PM, Jes Sorensen<Jes.Sorensen@redhat.com>  wrote:
>    
>> On 05/20/10 13:10, Avi Kivity wrote:
>>      
>>> 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 use the following.  It ain't pretty:
>
> #!/bin/bash
> cleanup() {
>          trap - 2
>          kill -2 $sleep_pid
>          echo 0>/sys/kernel/debug/tracing/events/kvm/enable
>          kill $cat_pid
> }
>
> perf stat -a -e 'kvm:*' sleep 1h>results/perf_stat 2>&1&
> sleep_pid=$(sleep 1&&  pgrep -x -f "sleep 1h")   # sleep 1 is to avoid
> race with forked perf process
> trap cleanup 2
> echo 1>/sys/kernel/debug/tracing/events/kvm/enable
> cat /sys/kernel/debug/tracing/trace_pipe>results/trace&
> cat_pid=$!
>
> # ...do stuff here...
>
> cleanup
>    

perf will enable the events by itself (no?), so all you need is is the 
perf call in the middle.

What's missing is vmstat-like or kvm_stat-like output, but that's 
another thing.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.