linux-kernel - Re: [RFC PATCH 0/2] kvm/vmx: Output TSC offset

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Message-ID: <1352860305.18025.48.camel@gandalf.local.home>
Date:	Tue, 13 Nov 2012 21:31:45 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	David Sharp <dhsharp@...gle.com>
Cc:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>,
	linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	kvm@...r.kernel.org, Joerg Roedel <joerg.roedel@....com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>,
	Ingo Molnar <mingo@...hat.com>, Avi Kivity <avi@...hat.com>,
	yrl.pp-manager.tt@...achi.com,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH 0/2] kvm/vmx: Output TSC offset

On Tue, 2012-11-13 at 18:03 -0800, David Sharp wrote:
> On Tue, Nov 13, 2012 at 6:00 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> > On Wed, 2012-11-14 at 10:36 +0900, Yoshihiro YUNOMAE wrote:
> >
> >> To merge the data like previous pattern, we apply this patch set. Then, we can
> >> get TSC offset of the guest as follows:
> >>
> >> $ dmesg | grep kvm
> >> [   57.717180] kvm: (2687) write TSC offset 18446743360465545001, now clock ##
> >>                      ^^^^                   ^^^^^^^^^^^^^^^^^^^^            |
> >>                      PID                         TSC offset                 |
> >>                                                            HOST TSC value --+
> >>
> >
> > Using printk to export something like this is IMO a nasty hack.
> >
> > Can't we create a /sys or /proc file to export the same thing?
> 
> Since the value changes over the course of the trace, and seems to be
> part of the context of the trace, I think I'd include it as a
> tracepoint.
> 

I'm fine with that too.

-- Steve


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