Messages in this thread | | | Date | Thu, 10 Jun 2010 09:31:42 +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) > > I.e. does the feature really give us the expected statistical stability in > results? Does it really exclude hardirq/softirq workloads, etc.? > > Thanks, > > Ingo
Just got some results:
$ sudo ./perf stat -e instructions -e cycles -e branches -e branch-misses -v -r 10 ./hackbench 5
Performance counter stats for './hackbench 5' (10 runs):
1313640764 instructions # 0,241 IPC ( +- 1,393% ) (scaled from 100,05%) 5440853130 cycles ( +- 0,925% ) (scaled from 100,05%) 214737441 branches ( +- 0,948% ) 12332109 branch-misses # 5,743 % ( +- 1,239% )
1,727051101 seconds time elapsed ( +- 0,897% )
$ sudo ./perf stat -e instructions:t -e cycles:t -e branches:t -e branch-misses:t -v -r 10 ./hackbench 5
Performance counter stats for './hackbench 5' (10 runs):
1293802776 instructions # 0,245 IPC ( +- 0,343% ) 5280769301 cycles ( +- 0,471% ) (scaled from 100,02%) 209495435 branches ( +- 0,392% ) 11890938 branch-misses # 5,676 % ( +- 0,491% )
1,750534923 seconds time elapsed ( +- 0,463% )
So yeah, the results look a bit better. Still not perfects:
- we are still instrumenting the tiny parts between the true interrupt and irq_enter() (same for irq_exit() and the end). Same for softirqs.
- random randomnesses...
Another try, this time with a kernel downloading in parallel, to generate network interrupts:
$ sudo ./perf stat -e instructions -e cycles -e branches -e branch-misses -v -r 10 ./hackbench 5
Performance counter stats for './hackbench 5' (10 runs):
1324759169 instructions # 0,244 IPC ( +- 0,494% ) (scaled from 100,09%) 5424824320 cycles ( +- 0,503% ) 214443106 branches ( +- 0,516% ) 12245614 branch-misses # 5,710 % ( +- 0,604% )
1,723413199 seconds time elapsed ( +- 0,483% )
$ sudo ./perf stat -e instructions:t -e cycles:t -e branches:t -e branch-misses:t -v -r 10 ./hackbench 5
Performance counter stats for './hackbench 5' (10 runs):
1292119132 instructions # 0,251 IPC ( +- 0,138% ) 5138407131 cycles ( +- 2,708% ) 209052068 branches ( +- 0,139% ) 11835090 branch-misses # 5,661 % ( +- 0,105% )
1,752192124 seconds time elapsed ( +- 0,278% )
Again, globally better, except for the cycles this time.
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