Re: [patch] perf_counter tools: remove expensive old debug codefrom perf top
From: Ingo Molnar
Date: Tue Oct 13 2009 - 09:38:45 EST
* Mike Galbraith <efault@xxxxxx> 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.
Ingo
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