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Date: Sat, 06 Nov 2010 02:05:57 +0900 From: Hitoshi Mitake <mitake@....info.waseda.ac.jp> To: Ingo Molnar <mingo@...e.hu> CC: linux-kernel@...r.kernel.org, h.mitake@...il.com, Ma Ling <ling.ma@...el.com>, Zhao Yakui <yakui.zhao@...el.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Arnaldo Carvalho de Melo <acme@...hat.com>, Paul Mackerras <paulus@...ba.org>, Frederic Weisbecker <fweisbec@...il.com>, Steven Rostedt <rostedt@...dmis.org>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com> Subject: Re: [PATCH 2/2] perf bench: add x86-64 specific benchmarks to perf bench mem memcpy On 2010年11月01日 18:02, Ingo Molnar wrote: > > * Hitoshi Mitake<mitake@....info.waseda.ac.jp> wrote: > >> On 2010年10月31日 04:23, Ingo Molnar wrote: >>> >>> * Hitoshi Mitake<mitake@....info.waseda.ac.jp> wrote: >>> >>>> This patch adds new file: mem-memcpy-x86-64-asm.S >>>> for x86-64 specific memcpy() benchmarking. >>>> Added new benchmarks are, >>>> x86-64-rep: memcpy() implemented with rep instruction >>>> x86-64-unrolled: unrolled memcpy() >>>> >>>> Original idea of including the source files of kernel >>>> for benchmarking is suggested by Ingo Molnar. >>>> This is more effective than write-once programs for quantitative >>>> evaluation of in-kernel, little and leaf functions called high frequently. >>>> Because perf bench is in kernel source tree and executing it >>>> on various hardwares, especially new model CPUs, is easy. >>>> >>>> This way can also be used for other functions of kernel e.g. checksum functions. >>>> >>>> Example of usage on Core i3 M330: >>>> >>>> | % ./perf bench mem memcpy -l 500MB >>>> | # Running mem/memcpy benchmark... >>>> | # Copying 500MB Bytes from 0x7f911f94c010 to 0x7f913ed4d010 ... >>>> | >>>> | 578.732506 MB/Sec >>>> | % ./perf bench mem memcpy -l 500MB -r x86-64-rep >>>> | # Running mem/memcpy benchmark... >>>> | # Copying 500MB Bytes from 0x7fb4b6fe4010 to 0x7fb4d63e5010 ... >>>> | >>>> | 738.184980 MB/Sec >>>> | % ./perf bench mem memcpy -l 500MB -r x86-64-unrolled >>>> | # Running mem/memcpy benchmark... >>>> | # Copying 500MB Bytes from 0x7f6f2e668010 to 0x7f6f4da69010 ... >>>> | >>>> | 767.483269 MB/Sec >>>> >>>> This shows clearly that unrolled memcpy() is efficient >>>> than rep version and glibc's one :) >>> >>> Hey, really cool output :-) >>> >>> Might also make sense to measure Ma Ling's patched version? >> >> Does Ma Ling's patched version mean, >> >> http://marc.info/?l=linux-kernel&m=128652296500989&w=2 >> >> the memcpy applied the patch of the URL? >> (It seems that this patch was written by Miao Xie.) >> >> I'll include the result of patched version in the next post. > > (Indeed it is Miao Xie - sorry!) > >>>> # checkpatch.pl warns about two externs in bench/mem-memcpy.c >>>> # added by this patch. But I think it is no problem. >>> >>> You should put these: >>> >>> +#ifdef ARCH_X86_64 >>> +extern void *memcpy_x86_64_unrolled(void *to, const void *from, size_t len); >>> +extern void *memcpy_x86_64_rep(void *to, const void *from, size_t len); >>> +#endif >>> >>> into a .h file - a new one if needed. >>> >>> That will make both checkpatch and me happier ;-) >>> >> >> OK, I'll separate these files. >> >> BTW, I found really interesting evaluation result. >> Current results of "perf bench mem memcpy" include >> the overhead of page faults because the measured memcpy() >> is the first access to allocated memory area. >> >> I tested the another version of perf bench mem memcpy, >> which does memcpy() before measured memcpy() for removing >> the overhead come from page faults. >> >> And this is the result: >> >> % ./perf bench mem memcpy -l 500MB -r x86-64-unrolled >> # Running mem/memcpy benchmark... >> # Copying 500MB Bytes from 0x7f19d488f010 to 0x7f19f3c90010 ... >> >> 4.608340 GB/Sec >> >> % ./perf bench mem memcpy -l 500MB >> # Running mem/memcpy benchmark... >> # Copying 500MB Bytes from 0x7f696c3cc010 to 0x7f698b7cd010 ... >> >> 4.856442 GB/Sec >> >> % ./perf bench mem memcpy -l 500MB -r x86-64-rep >> # Running mem/memcpy benchmark... >> # Copying 500MB Bytes from 0x7f45d6cff010 to 0x7f45f6100010 ... >> >> 6.024445 GB/Sec >> >> The relation of scores reversed! >> I cannot explain the cause of this result, and >> this is really interesting phenomenon. > > Interesting indeed, and it would be nice to analyse that! (It should be possible, > using various PMU metrics in a clever way, to figure out what's happening inside the > CPU, right?) > >> So I'd like to add new command line option, >> like "--pre-page-faults" to perf bench mem memcpy, >> for doing memcpy() before measured memcpy(). >> >> How do you think about this idea? > > Agreed. (Maybe name it --prefault, as 'prefaulting' is the term we generally use for > things like this.) > > An even better solution would be to output _both_ results by default, so that people > can see both characteristics at a glance? Outputting both result of prefaulted and non prefaulted will be useful, but this might be not good for using from scripts. So I'll implement --prefault option first. If there is request for outputting both, I'll consider to modify default output. # Please wait about the result of Miao Xie's patch, # benchmarking memcpy() of unaligned memory area is # a little difficult Thanks, Hitoshi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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