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SubjectRe: [PATCH v5 0/3] lib: find_*_bit reimplementation
On Sun, 22 Feb 2015 20:24:14 +0300 Yury Norov <yury.norov@gmail.com> wrote:

> This patchset does rework find_bit functions family to achieve better
> performance, and decrease size of text. All rework is done in patch 1.
> Patches 2 and 3 are about code moving and renaming.
>
> It was boot-tested on x86_64 and MIPS (big-endian) machines.
> Performance tests were ran on userspace with code like this:
>
> /* addr[] is filled from /dev/urandom */
> start = clock();
> while (ret < nbits)
> ret = find_next_bit(addr, nbits, ret + 1);
>
> end = clock();
> printf("%ld\t", (unsigned long) end - start);
>
> On Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz measuremets are next:
> (for find_next_bit, nbits is 8M, for find_first_bit - 80K)
>
> find_next_bit: find_first_bit:
> new current new current
> 26932 43151 14777 14925
> 26947 43182 14521 15423
> 26507 43824 15053 14705
> 27329 43759 14473 14777
> 26895 43367 14847 15023
> 26990 43693 15103 15163
> 26775 43299 15067 15232
> 27282 42752 14544 15121
> 27504 43088 14644 14858
> 26761 43856 14699 15193
> 26692 43075 14781 14681
> 27137 42969 14451 15061
> ... ...
>
> find_next_bit performance gain is 35-40%;
> find_first_bit - no measurable difference.
>
> On ARM machine, there is arch-specific implementation for find_bit.
> To disable it, and use generic one, please apply next patch:

I avoid putting patches into changelogs because in some situations
patch(1) tries to apply it when you apply the real patch. Maybe you
can share the userspace test harness with someone who has access to an
arm machine?

Patches 2 and 3 are missing your signed-off-by:. I added it to my
copies of those patches.



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