From: "H.J. Lu" <hjl.tools@gmail.com>
To: Florian Weimer <fweimer@redhat.com>
Cc: "H.J. Lu via Libc-alpha" <libc-alpha@sourceware.org>,
Arjan van de Ven <arjan@linux.intel.com>,
Hongyu Wang <hongyu.wang@intel.com>,
liuhongt <hongtao.liu@intel.com>,
Thiago Macieira <thiago.macieira@intel.com>
Subject: Re: [PATCH] x86: Don't set Prefer_No_AVX512 for processors with AVX512 and AVX-VNNI
Date: Tue, 7 Dec 2021 06:15:57 -0800 [thread overview]
Message-ID: <CAMe9rOqwUwEZjUF=wonTAAxJyrj5eD2wApe0bUHC+sam005y6Q@mail.gmail.com> (raw)
In-Reply-To: <87r1aoqzlz.fsf@oldenburg.str.redhat.com>
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.
--
H.J.
next prev parent reply other threads:[~2021-12-07 14:16 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 [this message]
2021-12-07 15:47 ` Florian Weimer
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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