From: "H.J. Lu" <hjl.tools@gmail.com>
To: Sunil Pandey <skpgkp2@gmail.com>
Cc: abush wang <abushwangs@gmail.com>,
Noah Goldstein <goldstein.w.n@gmail.com>,
abushwang via Libc-alpha <libc-alpha@sourceware.org>
Subject: Re: x86-64: strlen-evex performance performance degradation compared to strlen-avx2
Date: Mon, 29 Apr 2024 19:51:37 -0700 [thread overview]
Message-ID: <CAMe9rOqjSmKOGyghRhZJcJz3woEH0CbOC_PAm4UaJiPuuChgag@mail.gmail.com> (raw)
In-Reply-To: <CAMAf5_d1LzwFv+AuU1Wq20J-+EJPki9Zfb1GF2xtju_psLZk5Q@mail.gmail.com>
On Mon, Apr 29, 2024 at 5:55 PM Sunil Pandey <skpgkp2@gmail.com> wrote:
>
>
>
> On Mon, Apr 29, 2024 at 1:20 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>>
>> On Mon, Apr 29, 2024 at 10:42 AM Sunil Pandey <skpgkp2@gmail.com> wrote:
>> >
>> >
>> >
>> > On Sun, Apr 28, 2024 at 9:17 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>> >>
>> >> On Sun, Apr 28, 2024 at 9:13 AM Sunil Pandey <skpgkp2@gmail.com> wrote:
>> >> >
>> >> >
>> >> >
>> >> > On Sat, Apr 27, 2024 at 7:13 PM abush wang <abushwangs@gmail.com> wrote:
>> >> >>
>> >> >> Actually, I was handling performance issue from libmicro in our distro OS.
>> >> >> I found that the performance degradation of localtime_r benchmark from libmicro is blame to strlen.
>> >> >> So I abstracted this test case.
>> >> >>
>> >> >
>> >> > Can you consistently reproduce strlen perf behaviour by running multiple times back-to-back?
>> >> >
>> >> > You can see high swing from run
>> >>
>> >> Hi Sunil,
>> >>
>> >> Intel(R) Xeon(R) Gold 6133 CPU @ 2.50GHz is SKX. Please add this test to
>> >> benchtests/bench-strlen.c and check its performance on SKX.
>> >>
>> >> --
>> >> H.J.
>> >
>> >
>> > I collected the glibc micro-benchmark data for the string length in question.
>> >
>> > 2.38 evex data:
>> >
>> > length=4, alignment=4: 4.40
>> > length=4, alignment=0: 4.29
>> > length=4, alignment=0: 3.64
>> > length=4, alignment=7: 3.64
>> > length=4, alignment=2: 3.64
>> >
>> > 2.28 evex data:
>> >
>> > Length 4, alignment 4: 6.46875
>> > Length 4, alignment 0: 6.5
>> > Length 4, alignment 0: 6.53125
>> > Length 4, alignment 7: 6.46875
>> > Length 4, alignment 2: 6.53125
>> >
>> > Data collected on Machine: Intel(R) Xeon(R) Gold 6148 CPU @ 2.40GHz
>> >
>> > 2.38 perf numbers are better than 2.28 as expected.
>>
>> 1. Please compare AVX2 vs EVEX strlen on glibc master branch.
>> 2. Please check strlen on strings of length == 4 and alignments = 0, 1, 2, 3.
>>
>> --
>> H.J.
>
>
> Data from master branch:
>
> Data collected on Machine: Intel(R) Xeon(R) Gold 6148 CPU @ 2.40GHz
>
> __strlen_evex __strlen_avx2
> =======================================================
> length=4, alignment=0: 5.00 5.11
> length=4, alignment=1: 4.92 4.80
> length=4, alignment=2: 4.82 4.62
> length=4, alignment=3: 4.62 4.92
> length=4, alignment=4: 4.44 4.44
> length=4, alignment=5: 4.59 4.29
> length=4, alignment=6: 4.39 4.29
> length=4, alignment=7: 4.14 4.14
> length=4, alignment=8: 4.19 4.00
> length=4, alignment=9: 4.00 4.00
> length=4, alignment=10: 4.31 3.87
> length=4, alignment=11: 3.96 3.87
> length=4, alignment=12: 3.86 3.75
> length=4, alignment=13: 3.75 3.75
> length=4, alignment=14: 3.64 3.64
> length=4, alignment=15: 3.64 3.72
> length=4, alignment=16: 3.64 3.53
> length=4, alignment=17: 3.63 3.53
> length=4, alignment=18: 4.12 3.53
> length=4, alignment=19: 3.43 3.43
> length=4, alignment=20: 3.43 3.43
> length=4, alignment=21: 3.33 3.33
> length=4, alignment=22: 3.33 3.42
> length=4, alignment=23: 3.33 3.33
> length=4, alignment=24: 3.33 3.33
> length=4, alignment=25: 3.33 3.33
> length=4, alignment=26: 3.96 3.33
> length=4, alignment=27: 3.33 3.41
> length=4, alignment=28: 3.33 3.33
> length=4, alignment=29: 3.41 3.33
> length=4, alignment=30: 3.33 3.41
> length=4, alignment=31: 3.33 3.33
>
> --Sunil
Hi Sunil,
strlen-avx2.S in glibc 2.28 release (tag glibc-2.28) is
different from strlen-avx2.S on master branch. Please
compare their performances.
--
H.J.
next prev parent reply other threads:[~2024-04-30 2:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-26 4:03 x86-64: strlen-evex performance performance degradation compared to strlen-avx2 abush wang
2024-04-26 13:30 ` H.J. Lu
2024-04-26 16:53 ` Sunil Pandey
2024-04-28 2:13 ` abush wang
2024-04-28 16:12 ` Sunil Pandey
2024-04-28 16:16 ` H.J. Lu
2024-04-29 17:41 ` Sunil Pandey
2024-04-29 20:19 ` H.J. Lu
2024-04-30 0:54 ` Sunil Pandey
2024-04-30 2:51 ` H.J. Lu [this message]
2024-04-30 20:16 ` Sunil Pandey
2024-04-28 2:06 ` abush wang
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