Em Thu, Jan 16, 2014 at 06:34:58PM +0100, Frederic Weisbecker escreveu: > On Thu, Jan 16, 2014 at 10:17:53AM +0900, Namhyung Kim wrote: > > I think if the sort key doesn't contain "symbol", unmatch case would be > > increased as more various callchains would go into a same entry. > > You mean -g fractal,0.5,callee,address ? > > Hmm, actually I haven't seen much difference there.
I guess he will, but will wait for Namhyung's final ack here, ok? - Arnaldo > > > > > >> > > >> > > > >> > This results in less comparisons performed by the CPU. > > >> > > >> Do you have any numbers? I suspect it'd not be a big change, but just > > >> curious. > > > > > > So I compared before/after the patchset (which include the cursor restore > > > removal) > > > with: > > > > > > 1) Some big hackbench-like load that generates > 200 MB perf.data > > > > > > perf record -g -- perf bench sched messaging -l $SOME_BIG_NUMBER > > > > > > 2) Compare before/after with the following reports: > > > > > > perf stat perf report --stdio > /dev/null > > > perf stat perf report --stdio -s sym > /dev/null > > > perf stat perf report --stdio -G > /dev/null > > > perf stat perf report --stdio -g fractal,0.5,caller,address > /dev/null > > > > > > And most of the time I had < 0.01% difference on time completion in > > > favour of the patchset > > > (which may be due to the removed cursor restore patch eventually). > > > > > > So, all in one, there was no real interesting difference. If you want the > > > true results I can definetly relaunch the tests. > > > > So as an extreme case, could you please also test "-s cpu" case and > > share the numbers? > > There is indeed a tiny difference here. > > Before the patchset: > > fweisbec@Aivars:~/linux-2.6-tip/tools/perf$ sudo ./perf stat -r 20 ./perf > report --stdio -s cpu > /dev/null > > Performance counter stats for './perf report --stdio -s cpu' (20 runs): > > 3343,047232 task-clock (msec) # 0,999 CPUs utilized > ( +- 0,12% ) > 6 context-switches # 0,002 K/sec > ( +- 3,82% ) > 0 cpu-migrations # 0,000 K/sec > > 128 076 page-faults # 0,038 M/sec > ( +- 0,00% ) > 13 044 840 323 cycles # 3,902 GHz > ( +- 0,12% ) > <not supported> stalled-cycles-frontend > <not supported> stalled-cycles-backend > 16 341 506 514 instructions # 1,25 insns per cycle > ( +- 0,00% ) > 4 042 448 707 branches # 1209,211 M/sec > ( +- 0,00% ) > 26 819 441 branch-misses # 0,66% of all branches > ( +- 0,09% ) > > 3,345286450 seconds time elapsed > ( +- 0,12% ) > > After the patchset: > > fweisbec@Aivars:~/linux-2.6-tip/tools/perf$ sudo ./perf stat -r 20 ./perf > report --stdio -s cpu > /dev/null > > Performance counter stats for './perf report --stdio -s cpu' (20 runs): > > 3365,739972 task-clock (msec) # 0,999 CPUs utilized > ( +- 0,12% ) > 6 context-switches # 0,002 K/sec > ( +- 2,99% ) > 0 cpu-migrations # 0,000 K/sec > > 128 076 page-faults # 0,038 M/sec > ( +- 0,00% ) > 13 133 593 870 cycles # 3,902 GHz > ( +- 0,12% ) > <not supported> stalled-cycles-frontend > <not supported> stalled-cycles-backend > 16 626 286 378 instructions # 1,27 insns per cycle > ( +- 0,00% ) > 4 119 555 502 branches # 1223,967 M/sec > ( +- 0,00% ) > 28 687 283 branch-misses # 0,70% of all branches > ( +- 0,09% ) > > 3,367984867 seconds time elapsed > ( +- 0,12% ) > > > Which makes about 0.6% difference on the overhead. > Now it had less overhead in common cases (default sorting, -s sym, -G, > etc...). > I guess it's not really worrysome, it's mostly unvisible at this scale. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
