Messages in this thread | | | Date | Mon, 27 Jul 2009 22:19:47 -0400 (EDT) | From | Steven Rostedt <> | Subject | Re: [PATCH 0/3] Add walltime support for ring-buffer |
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On Tue, 28 Jul 2009, Frederic Weisbecker wrote: > > > > In nowadays, many workload run on cluster machine environment. Then > > We often need compare different machines tracing log. it mean TSC isn't > > sufficient. but nobody want performance reduce. > > Fortunatelly, ntp time adjustment is not happend so frequently. we > > don't need wall-time on _every_ event. > > > > Thanks. > > > Yeah, that would really slow the tracing. > > Can't we get a snapshot of the couple (walltime, cpu clock) once > at startup. > Then we can retrieve the walltime when cpu_clock was 0 and compute > the walltime for each traces at output time using the trace timestamp as > a delta?
This should be something in one of the trace clock sources. It can perhaps have a helper function called by gettimeofday or something, but it should be something that gets plugged into the ring buffer and not something that needs to modify any of its code.
-- Steve
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