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SubjectRe: [patch] perf_counter tools: remove expensive old debug code from perf top
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On Tue, 2009-10-13 at 15:37 +0200, Ingo Molnar wrote:
> * Mike Galbraith <efault@gmx.de> wrote:
>
> > perf_counter tools: remove expensive old debug code from perf top
> >
> > Calling gettimeofday() at high frequency is painful for handicapped
> > boxen. The spot calling gettimeofday() is old unneeded debug code, so
> > remove it.
>
> Thanks!
>
> We still seem to have a performance problem. Just running perf top on a
> 16-way box:
>
> Performance counter stats for 'perf top -e cycles -c 3000000':
>
> 585.694831 task-clock-msecs # 0.113 CPUs
> 35163 context-switches # 0.060 M/sec
> 17 CPU-migrations # 0.000 M/sec
> 20355 page-faults # 0.035 M/sec
> 1476952962 cycles # 2521.711 M/sec
> 730770658 instructions # 0.495 IPC
> 11489471 cache-references # 19.617 M/sec
> 2055001 cache-misses # 3.509 M/sec
>
> 5.169518576 seconds time elapsed
>
> that's 11% of CPU time used on a single CPU - just displaying a measly
> 16K irqs/sec. Something's not quite right here.

I'll try to figure out why after I do some more wakeup preempt testing.

btw, something broke top annotation (again). Module symbols still
annotate, but vmlinux symbols went south.

-Mike



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