From: Ingo Molnar <mingo@elte.hu>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: "Nikanth Karthikesan" <knikanth@suse.de>,
"Fr馘駻ic Weisbecker" <fweisbec@gmail.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org
Subject: Re: ftrace not working?
Date: Mon, 23 Mar 2009 15:32:26 +0100 [thread overview]
Message-ID: <20090323143226.GA18439@elte.hu> (raw)
In-Reply-To: <20090323200057.9027.A69D9226@jp.fujitsu.com>
* KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
> > On Monday 23 March 2009 14:05:33 Ingo Molnar wrote:
> > > one thing to note:
> > > | CPU0: Intel QEMU Virtual CPU version 0.9.1 stepping 03
> > > | Testing tracer nop: PASSED
> > >
> > > so it's a Qemu session, right?
> > >
> >
> > Yes. qemu-kvm.
>
> Ah, sorry. I don't know qemu and kvm at all ;)
In terms of tracing it should just look like some weird old CPU with
few capabilities and long delays. Nothing in ftrace depends on CPU
capabilities (that wasnt present in pentia) so this is weird.
Perhaps some timestamping problem? Virtual machines tend to have
trouble with the TSC. Or code patching problems? But that does not
explain the lack of explicit scheduler events.
Or perhaps the fact that qemu sessions tend to boot with barely any
RAM. Maybe the ringbuffer size is very low?
Ingo
next prev parent reply other threads:[~2009-03-23 14:32 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-23 6:38 ftrace not working? Nikanth Karthikesan
2009-03-23 7:15 ` Frederic Weisbecker
2009-03-23 8:41 ` Frederic Weisbecker
2009-03-23 8:44 ` Nikanth Karthikesan
2009-03-23 11:25 ` Frederic Weisbecker
2009-03-23 11:33 ` Nikanth Karthikesan
2009-03-23 8:08 ` KOSAKI Motohiro
2009-03-23 8:27 ` Nikanth Karthikesan
2009-03-23 8:35 ` Ingo Molnar
2009-03-23 8:38 ` Nikanth Karthikesan
2009-03-23 11:01 ` KOSAKI Motohiro
2009-03-23 14:32 ` Ingo Molnar [this message]
2009-03-24 17:23 ` Nikanth Karthikesan
2009-03-24 20:13 ` Frederic Weisbecker
2009-03-25 2:21 ` Steven Rostedt
2009-03-25 4:06 ` Nikanth Karthikesan
2009-03-25 4:19 ` Steven Rostedt
2009-03-25 1:08 ` Rusty Russell
2009-03-25 3:21 ` KOSAKI Motohiro
2009-03-25 7:27 ` Ingo Molnar
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