Messages in this thread | | | Date | Thu, 10 Jun 2010 09:15:19 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 0/5] perf events finer grained context instrumentation / context exclusion |
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On Thu, Jun 10, 2010 at 08:26:18AM +0200, Ingo Molnar wrote: > > * Frederic Weisbecker <fweisbec@gmail.com> wrote: > > > Here is the new version of per context exclusion, based on hooks on > > irq_enter/irq_exit. I haven't observed slowdowns but I haven't actually > > measured the impact. > > One thing that would be nice to see in this discussion is a comparison of > before/after perf stat --repeat runs. > > Something like: > > perf stat --repeat ./hackbench 5 > > Done with full stat, and then also done with hardirqs/softirqs excluded. (i.e. > task context stats only)
Right, so I just tried each perf stat default events with :t and it hung up ;-)
(Not severely, I can kill perf stat with ^Z, but still there is something I need to fix).
> > I.e. does the feature really give us the expected statistical stability in > results? Does it really exclude hardirq/softirq workloads, etc.?
But yeah, before posting these patches I gave that a try with the instruction counter and it didn't change much against the usual results, it's about the same variations.
I just know the exclusion works by using perf record -g / perf report, as the callchains are truly reliable against the exclusion rules, and since counting and samples are treated the same in this scheme (we just deactivate /reactivate, there is no post blocking or fixup).
I just don't know where the entropy comes from. May be once I'll have the hang fixed I'll be able to test with all the default stat events and see a better overview of progress.
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