From: Sunil Pandey <skpgkp2@gmail.com>
To: "H.J. Lu" <hjl.tools@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 17:54:53 -0700 [thread overview]
Message-ID: <CAMAf5_d1LzwFv+AuU1Wq20J-+EJPki9Zfb1GF2xtju_psLZk5Q@mail.gmail.com> (raw)
In-Reply-To: <CAMe9rOrEX=Oe=5mvdcbWfHfjSwhiekbe+NsGH3L8qZXp2k6mRw@mail.gmail.com>
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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
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next prev parent reply other threads:[~2024-04-30 0:56 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 [this message]
2024-04-30 2:51 ` H.J. Lu
2024-04-30 20:16 ` Sunil Pandey
2024-04-28 2:06 ` abush wang
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