Re: [PATCH 2/2] perf bench: add x86-64 specific benchmarks to perfbench mem memcpy

[Hitoshi Mitake]

On 2010å10æ31æ 04:23, Ingo Molnar wrote:
> * Hitoshi Mitake<mitake@xxxxxxxxxxxxxxxxxxxxx>  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.

> > # 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.

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?

Thanks,
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