Messages in this thread | | | Date | Mon, 1 Nov 2010 10:02:51 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 2/2] perf bench: add x86-64 specific benchmarks to perf bench mem memcpy |
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* Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> wrote:
> On 2010年10月31日 04:23, Ingo Molnar wrote: > > > >* Hitoshi Mitake<mitake@dcl.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?
Thanks,
Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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