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

[Stephane Eranian]

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.

> 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.
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