From: Florian Weimer <fweimer@redhat.com>
To: "H.J. Lu via Libc-alpha" <libc-alpha@sourceware.org>
Cc: "H.J. Lu" <hjl.tools@gmail.com>,
Arjan van de Ven <arjan@linux.intel.com>,
liuhongt <hongtao.liu@intel.com>,
Thiago Macieira <thiago.macieira@intel.com>,
Hongyu Wang <hongyu.wang@intel.com>
Subject: Re: [PATCH] x86: Don't set Prefer_No_AVX512 for processors with AVX512 and AVX-VNNI
Date: Tue, 07 Dec 2021 16:47:59 +0100 [thread overview]
Message-ID: <878rwwquvk.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <CAMe9rOqwUwEZjUF=wonTAAxJyrj5eD2wApe0bUHC+sam005y6Q@mail.gmail.com> (H. J. Lu via Libc-alpha's message of "Tue, 7 Dec 2021 06:15:57 -0800")
* H. J. Lu via Libc-alpha:
> On Tue, Dec 7, 2021 at 6:05 AM Florian Weimer <fweimer@redhat.com> wrote:
>>
>> * H. J. Lu via Libc-alpha:
>>
>> > Hongtao, Hongyu, can you find a Rocket Lake to test?
>>
>> I've found a lab machine with an i7-11700 CPU. Is there something I
>> could test for you?
>
> You can enable AVX512 in glibc with:
>
> $ export GLIBC_TUNABLES=glibc.cpu.hwcaps=-Prefer_No_AVX512
>
> While bootstrapping GCC with -j8, track CPU frequency with turbostat. If
> there is no CPU frequency drop and build time is less comparing against
> without GLIBC_TUNABLES, we can enable AVX512.
>
>> (This could be non-production silicon, though.)
>>
>
> The frequency behavior of non-production silicon can be different.
With that caveat, it seems that frequencies drop further with
GLIBC_TUNABLES set as above, and the build is also a little bit slower
(5m31s vs 5m23s, the AVX-512 build was run first, and the systems was a
little bit warmer for the second run).
Would it make sense to run more extensive tests, or should we wait for
someone with production silicon to show up?
Thanks,
Florian
next prev parent reply other threads:[~2021-12-07 15:48 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-06 3:23 H.J. Lu
2021-12-07 7:47 ` Noah Goldstein
2021-12-07 12:53 ` H.J. Lu
2021-12-07 13:17 ` Arjan van de Ven
2021-12-07 13:34 ` H.J. Lu
2021-12-07 14:05 ` Florian Weimer
2021-12-07 14:15 ` H.J. Lu
2021-12-07 15:47 ` Florian Weimer [this message]
2021-12-07 15:52 ` H.J. Lu
2021-12-07 16:22 ` Thiago Macieira
2021-12-07 19:32 ` Noah Goldstein
2022-04-23 1:51 ` Sunil Pandey
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