From: Avi Kivity <avi@redhat.com>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Jes Sorensen <Jes.Sorensen@redhat.com>, kvm <kvm@vger.kernel.org>
Subject: Re: Wiki docs on counting and tracing KVM perf events
Date: Thu, 20 May 2010 14:10:57 +0300 [thread overview]
Message-ID: <4BF518C1.60304@redhat.com> (raw)
In-Reply-To: <AANLkTikkXtDFT9O_zHx4j1ziAdZQ7Ze2esfioO_JYHz4@mail.gmail.com>
On 05/20/2010 02:05 PM, Stefan Hajnoczi wrote:
> 8330 kvm:kvm_entry # 0.000 M/sec
> ^--- count since starting perf
>
> The 8330 number means that kvm_entry has fired 8330 times since perf
> was started. Like Avi says, you need to keep the perf process
> running. I run benchmarks using a script that kills perf after the
> benchmark completes.
>
> 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?
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
next prev parent reply other threads:[~2010-05-20 11:11 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-13 14:35 Wiki docs on counting and tracing KVM perf events Stefan Hajnoczi
2010-05-13 14:57 ` Avi Kivity
2010-05-20 8:15 ` Jes Sorensen
2010-05-20 8:19 ` Avi Kivity
2010-05-20 8:24 ` Jes Sorensen
2010-05-20 11:05 ` Stefan Hajnoczi
2010-05-20 11:10 ` Avi Kivity [this message]
2010-05-20 11:16 ` Jes Sorensen
2010-05-20 11:23 ` Stefan Hajnoczi
2010-05-20 12:14 ` Avi Kivity
2010-05-20 12:24 ` Stefan Hajnoczi
2010-05-20 12:37 ` Avi Kivity
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