Re: [BUG] perf: perf sched warning possibly due to clock granularityon AMD

[Stephane Eranian]

On Wed, Feb 8, 2012 at 4:22 PM, Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:
> On Wed, Feb 08, 2012 at 04:10:24PM +0100, Stephane Eranian wrote:
>> On Wed, Feb 8, 2012 at 4:07 PM, Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:
>> > On Mon, Feb 06, 2012 at 02:25:46PM +0100, Stephane Eranian wrote:
>> >> Hi,
>> >>
>> >> I am running 3.3.30-rc2 on an AMD Bulldozer system in 64-bit mode.
>> >> I was testing perf sched and I ran into an issue. That issue seems
>> >> to exist only on AMD and not on Intel systems. It is not PMU related
>> >> because I am doing tracing.
>> >>
>> >> I am running a simple ping pong test to stress the context switch
>> >> code. Two processes exchanging a byte through a pipe (program provided
>> >> below).
>> >>
>> >> Then, I capture a trace using perf sched, and I run sched lat, but
>> >> on certain runs, I get:
>> >>
>> >> Â Â$ perf sched rec pong 2
>> >> Â Â$ perf sched lat
>> >> Â Â ÂWarning: Timestamp below last timeslice flush
>> >> Â Â ÂWarning: Timestamp below last timeslice flush
>> >> Â Â ÂWarning: Timestamp below last timeslice flush
>> >> Â Â ÂWarning: Timestamp below last timeslice flush
>> >> Â Â ÂWarning: Timestamp below last timeslice flush
>> >> Â Â ÂWarning: Timestamp below last timeslice flush
>> >> Â Â ÂWarning: Timestamp below last timeslice flush
>> >> Â Â ÂWarning: Timestamp below last timeslice flush
>> >> Â Â ÂWarning: TimesFound 4934 unknown events!
>> >> Â Â ÂIs this an older tool processing a perf.data file generated by a more recent tool?
>> >
>> > I've tried to reproduce this on an AMD phenom but haven't got any such
>> > warning.
>> >
>> It does not happen at each run.
>
> Yeah I tried 5 times but wasn't lucky.

That's not enough!

>
>>
>> > Is there any chance you could "perf archive" your data and upload it somewhere
>> > I can fetch it from?
>> >
>> I can send you the perf.data in a private Email.
>
> Thanks!

Will dig it up and send it to you.
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