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Date:	Mon, 22 Dec 2014 17:33:20 +0900
From:	Masami Hiramatsu <>
To:	Divya Vyas <>
Cc:	Steven Rostedt <>,
	LKML <>,
	"" <>
Subject: Re: Merge ftrace data of host and guest


I'm working on trace-cmd virt-server feature. This is just a basic feature
to allow trace-cmd using virtio-trace (no time synchronizing).
I'll send the updated version of the series soon.

(2014/12/22 16:07), Divya Vyas wrote:
> Hi ,
> One more thing I want to add that Yoshihiro YUNOMAE's  trace-merge
> script does this time synchronization. We have to calculate guest
> offset and then subtract with host time .

Right, to complete this work we need trace-merge like merging feature.
I assume that we can do that by passing the offset of the timestamp
information with guest trace data (that is the simplest implementation).

However, currently trace-merge depends on x86 TSC, but some intel
processors TSC is not stable. That is current barrier of trace-merge.

Thank you,

> But it is not applying on current trace-cmd report output format and
> not giving desired output .
> Thanks,
> Divya Vyas
> On Mon, Dec 22, 2014 at 12:34 PM, Divya Vyas <> wrote:
>> Hi Steven,
>> I am sorry but I am very new to trace-cmd , that's why I didn't knew
>> what you are working on it.
>> I will explain you whole scenario , Actually I have multiple guests
>> and a host and I want to see all traces on a single file  with
>> trace-cmd report command and may be kernelshark also .
>> trace-cmd report -i guest.dat -i host.dat command is giving me all
>> traces is single file but the timestamp is different for guest . So
>> the challenge for me is to sync the timestamp of guest and host .  Can
>> you advise me something in this ? How can I sync gettimeofday clocks
>> of guest and host ?
>> and kernelshark doesnt take trace-cmd report input , I think it takes
>> guest.dat and host.dat .
>> Is there any other viewer available for ftrace ?
>> On Sat, Dec 20, 2014 at 10:40 AM, Steven Rostedt <> wrote:
>>> On Fri, Dec 19, 2014 at 05:52:52PM +0530, Divya Vyas wrote:
>>>> Hi,
>>> Hi, it would be  helpful if you Cc'd me. I would have responded quicker. Luckily,
>>> someone noticed this email and told me about it.
>>>> I think it is not desired output . Ths script is written for diffrent
>>>> format .ftrace format is ( trace-cmd report command generates) :
>>> I'm actually working on trace-cmd this week and hopefully I'll be able to release
>>> 2.5 by x-mas.
>>> I believe that Masami is going to start continuing work on the virt guest
>>> tracer for trace-cmd.
>>> Also, for now, for a crud way of merging, if both the gettimeofday clocks
>>> of the host and guest are synced, you could do:
>>> guest> trace-cmd record -o guest.dat --date  ...
>>> host> trace-cmd record -o host.dat --date ...
>>> and then run:
>>> trace-cmd report -i guest.dat -i host.dat
>>> and trace-cmd will merge the two. The --date will add a way to sync the trace
>>> timestamps to a wall clock and that will be used to try to interleave the
>>> events of both the data files.
>>> -- Steve

Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory

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