From: Stefan Hajnoczi <stefanha@gmail.com>
To: Mohamad Gebai <mohamad.gebai@polymtl.ca>
Cc: kvm@vger.kernel.org, linux-perf-users@vger.kernel.org
Subject: Re: Tracing kvm: kvm_entry and kvm_exit
Date: Mon, 25 Feb 2013 11:18:04 +0100 [thread overview]
Message-ID: <20130225101804.GC2790@stefanha-thinkpad.redhat.com> (raw)
In-Reply-To: <1361550867.51279e13338a7@www.imp.polymtl.ca>
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
Perhaps there is a code path that is missing trace_kvm_exit().
We didn't investigate why it happens but the unexplained kvm_entry
events only appeared at the beginning of the trace, so the theory was
that events are not activated atomically by perf(1).
CCing perf mailing list.
It would be interesting if someone knows the answer.
Stefan
next parent reply other threads:[~2013-02-25 10:18 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 ` Stefan Hajnoczi [this message]
2013-02-26 16:24 ` Tracing kvm: kvm_entry and kvm_exit Mohamad Gebai
2013-02-26 16:32 ` Gleb Natapov
2013-02-27 16:39 ` David Ahern
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130225101804.GC2790@stefanha-thinkpad.redhat.com \
--to=stefanha@gmail.com \
--cc=kvm@vger.kernel.org \
--cc=linux-perf-users@vger.kernel.org \
--cc=mohamad.gebai@polymtl.ca \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).