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SubjectRe: [PATCH RFC] [X86] performance improvement for memcpy_64.S by avoid memory miss predication.

* Ling Ma <linguranus@gmail.com> wrote:

> Hi Ingo
> Thanks for your suggestion. I used 'perf stat --repeat 10
> /develop/trunk/memcpy/static' to measure before/after patch.
>
> The test program I wrote:
> for (i = 64; i < 4096 *4; i ++)
> do_memcpy(src, dst, i);
>
> when src offset is 0xbe000, dst is 0xad008, the measured result:
>
> Before patch:
> Performance counter stats for '/develop/trunk/memcpy/static' (10 runs):
> <not counted> task-clock-msecs
> <not counted> context-switches
> <not counted> CPU-migrations
> <not counted> page-faults
> <not counted> cycles
> <not counted> instructions
> <not counted> cache-references
> <not counted> cache-misses
> 37.408743997 seconds time elapsed ( +- 0.222% )

hm, on what kind of CPU have you run this? Why are those events not
counting? Is it some older, Pentium-4 alike CPU perhaps?

Ingo


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