From: David Ahern <dsahern@gmail.com>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Mohamad Gebai <mohamad.gebai@polymtl.ca>,
kvm@vger.kernel.org, linux-perf-users@vger.kernel.org
Subject: Re: Tracing kvm: kvm_entry and kvm_exit
Date: Wed, 27 Feb 2013 09:39:14 -0700 [thread overview]
Message-ID: <512E36B2.5090100@gmail.com> (raw)
In-Reply-To: <20130225101804.GC2790@stefanha-thinkpad.redhat.com>
On 2/25/13 3:18 AM, Stefan Hajnoczi wrote:
> On Fri, Feb 22, 2013 at 11:34:27AM -0500, Mohamad Gebai wrote:
>> I am tracing kvm using perf and I am analyzing the sequences of kvm_entry and
>> kvm_exit tracepoints.
>> I noticed that during the boot process of a VM, there are a lot more (2 to 3 as
>> many times) kvm_entry event than there are kvm_exit. I tried looking around but
>> didn't find anything that explains this. Is this missing instrumentation? Or
>> what other path does kvm take that doesn't generate a kvm_exit event?
>
> Gleb Natapov noticed something similar when playing with the perf script
> I posted here:
>
> http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/104181
Have you tried using perf kvm stat? It is really easy to add a
flag/option to dump individual analysis points with the stats summary at
the end - or only dump data points greater than some threshold.
Latest version for the 'live mode' can be found here:
https://github.com/dsahern/linux/tree/perf-kvm-live-3.8
>
> Perhaps there is a code path that is missing trace_kvm_exit().
I have been playing with the live mode a bit lately. I'll add a debug to
note 2 consecutive entry events without an exit -- see if it sheds some
light on it.
David
next prev parent reply other threads:[~2013-02-27 16:39 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1361550867.51279e13338a7@www.imp.polymtl.ca>
2013-02-25 10:18 ` Tracing kvm: kvm_entry and kvm_exit Stefan Hajnoczi
2013-02-26 16:24 ` Mohamad Gebai
2013-02-26 16:32 ` Gleb Natapov
2013-02-27 16:39 ` David Ahern [this message]
2013-02-28 4:49 ` David Ahern
2013-02-28 8:44 ` Stefan Hajnoczi
2013-03-04 5:36 ` Mohamad Gebai
2013-03-04 5:40 ` David Ahern
2013-03-04 6:15 ` Mohamad Gebai
2013-03-05 17:23 ` David Ahern
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