From: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: David Sharp <dhsharp@google.com>,
"H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Joerg Roedel <joerg.roedel@amd.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>,
Ingo Molnar <mingo@redhat.com>, Avi Kivity <avi@redhat.com>,
yrl.pp-manager.tt@hitachi.com,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: Re: Re: [RFC PATCH 0/2] kvm/vmx: Output TSC offset
Date: Tue, 20 Nov 2012 19:38:53 +0900 [thread overview]
Message-ID: <50AB5DBD.5050901@hitachi.com> (raw)
In-Reply-To: <1353078354.7586.14.camel@gandalf.local.home>
Hi Steven,
Sorry for the late reply.
(2012/11/17 0:05), Steven Rostedt wrote:
> On Wed, 2012-11-14 at 17:26 +0900, Yoshihiro YUNOMAE wrote:
>> Thank you for commenting on my patch set.
>>
>> (2012/11/14 11:31), Steven Rostedt wrote:
>>> On Tue, 2012-11-13 at 18:03 -0800, David Sharp wrote:
>>>> On Tue, Nov 13, 2012 at 6:00 PM, Steven Rostedt <rostedt@goodmis.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.
>>
>> Using some tracepoint is a nice idea, but there is one problem. Here,
>> our discussion point is "the event which TSC offset is changed does not
>> frequently occur, but the buffer must keep the event data."
>
> If you can hold off a bit, for the 3.9 window, I plan on pushing
> multiple buffers for ftrace. That is, you can create a separate buffer
> just for the TSC offset events:
>
> cd /sys/kernel/debug
> echo tsc > instances/new
> echo 1 > instances/tsc/events/tsc/offset/enable
>
> Then the buffer will be used only for that event.
That's good. The tracepoint will output as follows:
qemu-kvm-12345 [000] ....123456789: kvm_write_tsc_offset:
now_tsc=123456789 previous_offset=0 next_offset=123456780
Thanks,
--
Yoshihiro YUNOMAE
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: yoshihiro.yunomae.ez@hitachi.com
next prev parent reply other threads:[~2012-11-20 10:38 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-14 1:36 [RFC PATCH 0/2] kvm/vmx: Output TSC offset Yoshihiro YUNOMAE
2012-11-14 1:36 ` [RFC PATCH 1/2] kvm/vmx: Print TSC_OFFSET information when TSC offset value is written to VMCS Yoshihiro YUNOMAE
2012-11-14 1:37 ` [RFC PATCH 2/2] tools: Add a tool for merging trace data of a guest and a host Yoshihiro YUNOMAE
2012-11-14 2:00 ` [RFC PATCH 0/2] kvm/vmx: Output TSC offset Steven Rostedt
2012-11-14 2:02 ` H. Peter Anvin
2012-11-14 2:03 ` David Sharp
2012-11-14 2:31 ` Steven Rostedt
2012-11-14 8:26 ` Yoshihiro YUNOMAE
2012-11-16 15:05 ` Steven Rostedt
2012-11-16 18:56 ` Marcelo Tosatti
2012-11-20 10:38 ` Yoshihiro YUNOMAE [this message]
2012-11-16 19:15 ` Marcelo Tosatti
2012-11-20 10:36 ` Yoshihiro YUNOMAE
2012-11-20 22:51 ` Marcelo Tosatti
2012-11-22 5:21 ` Yoshihiro YUNOMAE
2012-11-23 22:46 ` Marcelo Tosatti
2012-11-26 11:05 ` Yoshihiro YUNOMAE
2012-11-26 23:16 ` Marcelo Tosatti
2012-11-27 10:53 ` Yoshihiro YUNOMAE
2012-11-29 22:51 ` Marcelo Tosatti
2012-11-30 1:36 ` Yoshihiro YUNOMAE
2012-11-30 20:42 ` Marcelo Tosatti
2012-12-03 0:55 ` Yoshihiro YUNOMAE
2012-11-16 3:19 ` Marcelo Tosatti
2012-11-16 8:09 ` Yoshihiro YUNOMAE
2012-11-16 10:05 ` Marcelo Tosatti
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