From: Andy Lutomirski <luto@kernel.org>
To: Len Brown <lenb@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>, Willy Tarreau <w@1wt.eu>,
Florian Weimer <fweimer@redhat.com>,
"Bae, Chang Seok" <chang.seok.bae@intel.com>,
Dave Hansen <dave.hansen@intel.com>, X86 ML <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-abi@vger.kernel.org,
"libc-alpha@sourceware.org" <libc-alpha@sourceware.org>,
Rich Felker <dalias@libc.org>, Kyle Huey <me@kylehuey.com>,
Keno Fischer <keno@juliacomputing.com>
Subject: Re: Candidate Linux ABI for Intel AMX and hypothetical new related features
Date: Fri, 16 Apr 2021 15:03:39 -0700 [thread overview]
Message-ID: <CALCETrVbbDm1P21yG4HWPCuipPdBT6-Kdd5sRZpaZjjQr9euDw@mail.gmail.com> (raw)
In-Reply-To: <CAJvTdKmDskNka9tm5TMZkkP8tYa-K01sz8hAMccRSaAYKNPz5Q@mail.gmail.com>
On Fri, Apr 16, 2021 at 2:54 PM Len Brown <lenb@kernel.org> wrote:
>
> On Thu, Apr 15, 2021 at 12:24 PM Andy Lutomirski <luto@kernel.org> wrote:
> > On Wed, Apr 14, 2021 at 2:48 PM Len Brown <lenb@kernel.org> wrote:
>
> > > > ... the transition penalty into and out of AMX code
>
> The concept of 'transition' exists between AVX and SSE instructions
> because it is possible to mix both instruction sets and touch different
> parts of the same registers. The "unused" parts of those registers
> need to be tracked to assure that data is not lost when mixing.
I get it. That does not explain why LDMXCSR and VLDMXCSR cause
pipelines stalls.
>
> This concept is moot with AMX, which has its own dedicated registers.
>
> > What is the actual impact of a trivial function that initializes the
> > tile config, does one tiny math op, and then does TILERELEASE?
^^^^ "does one tiny math op"
AVX-512 *also* has sort-of-dedicated registers: ZMM16 and up. I still
can't find any conclusive evidence as to whether that avoids the
performance hit.
Intel's track record at actually explaining what operations cause what
particular performance disasters is poor, and your explanation is not
helping the situation. Sorry.
next prev parent reply other threads:[~2021-04-16 22:04 UTC|newest]
Thread overview: 130+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-26 23:12 Candidate Linux ABI for Intel AMX and hypothetical new related features Andy Lutomirski
2021-03-26 23:18 ` Andy Lutomirski
2021-03-27 3:39 ` Len Brown
2021-03-27 9:14 ` Borislav Petkov
2021-03-27 9:58 ` Greg KH
2021-03-29 15:47 ` Len Brown
2021-03-29 16:38 ` Len Brown
2021-03-29 16:48 ` Florian Weimer
2021-03-29 18:14 ` Andy Lutomirski
2021-03-29 18:16 ` Andy Lutomirski
2021-03-29 22:38 ` Len Brown
2021-03-30 5:08 ` Andy Lutomirski
2021-03-30 5:50 ` Noah Goldstein
2021-03-30 17:01 ` Len Brown
2021-03-30 17:05 ` Andy Lutomirski
2021-03-30 17:56 ` Len Brown
2021-03-30 19:12 ` Dave Hansen
2021-03-30 20:20 ` Andy Lutomirski
2021-03-30 20:42 ` Len Brown
2021-03-30 22:01 ` David Laight
2021-03-31 16:31 ` Len Brown
2021-03-31 16:53 ` Andy Lutomirski
2021-03-31 21:42 ` Robert O'Callahan
2021-03-31 22:11 ` Len Brown
2021-03-31 22:28 ` Len Brown
2021-03-31 22:45 ` Andy Lutomirski
2021-04-09 20:52 ` Len Brown
2021-04-09 21:44 ` Andy Lutomirski
2021-04-11 19:07 ` Len Brown
2021-04-12 7:59 ` David Laight
2021-04-12 12:19 ` Borislav Petkov
2021-04-12 17:14 ` Sean Christopherson
2021-03-31 22:52 ` Borislav Petkov
2021-04-09 20:55 ` Len Brown
2021-03-28 0:53 ` Thomas Gleixner
2021-03-29 7:27 ` Peter Zijlstra
2021-03-29 15:06 ` Dave Hansen
2021-03-31 8:24 ` Borislav Petkov
[not found] ` <87lf9nk2ku.fsf@oldenburg.str.redhat.com>
2021-04-12 14:31 ` Borislav Petkov
2021-04-12 14:38 ` Florian Weimer
2021-04-12 15:08 ` Borislav Petkov
2021-04-12 15:10 ` Andy Lutomirski
2021-04-12 15:21 ` Andy Lutomirski
2021-04-12 23:46 ` Len Brown
2021-04-13 0:17 ` Thomas Gleixner
2021-04-13 1:25 ` Len Brown
2021-04-13 3:43 ` Willy Tarreau
2021-04-13 19:51 ` Len Brown
2021-04-14 9:58 ` Borislav Petkov
2021-04-14 10:06 ` Willy Tarreau
2021-04-14 10:08 ` Borislav Petkov
2021-04-14 21:57 ` Len Brown
2021-04-15 4:43 ` Borislav Petkov
2021-04-15 5:29 ` Willy Tarreau
2021-04-15 5:47 ` Borislav Petkov
2021-04-16 22:05 ` Len Brown
2021-04-19 14:14 ` Borislav Petkov
2021-04-19 18:18 ` Len Brown
2021-04-19 19:15 ` Borislav Petkov
2021-04-19 21:33 ` Len Brown
2021-04-19 21:58 ` Borislav Petkov
2021-04-23 19:35 ` Len Brown
2021-04-23 19:57 ` Borislav Petkov
2021-05-02 15:27 ` Len Brown
2021-05-03 5:18 ` Florian Weimer
2021-05-03 13:43 ` Dave Hansen
2021-05-03 13:47 ` Florian Weimer
2021-05-03 14:14 ` Dave Hansen
2021-05-07 18:44 ` Thomas Gleixner
2021-05-07 18:50 ` Andy Lutomirski
2021-05-07 19:22 ` Thomas Gleixner
2021-05-08 9:45 ` Thomas Gleixner
2021-05-18 20:39 ` Len Brown
2021-05-19 23:29 ` Andy Lutomirski
2021-05-20 19:16 ` Len Brown
2021-05-17 9:45 ` Thomas Gleixner
2021-05-17 9:56 ` Florian Weimer
2021-05-17 10:18 ` Thomas Gleixner
2021-05-21 16:29 ` Len Brown
2021-05-17 13:49 ` Arjan van de Ven
2021-05-20 15:35 ` Len Brown
2021-05-20 20:54 ` Thomas Gleixner
2021-05-20 21:13 ` Dave Hansen
2021-05-20 21:41 ` Len Brown
2021-05-20 22:53 ` Dave Hansen
2021-05-21 9:41 ` Thomas Gleixner
2021-05-21 14:44 ` Florian Weimer
2021-05-21 14:49 ` Peter Zijlstra
2021-06-23 15:06 ` Florian Weimer
2021-06-23 23:11 ` Len Brown
2021-06-28 10:14 ` Enrico Weigelt, metux IT consult
2021-06-28 12:49 ` Florian Weimer
2021-06-30 12:22 ` Enrico Weigelt, metux IT consult
2021-06-30 12:41 ` Willy Tarreau
2021-06-30 13:55 ` Arjan van de Ven
2021-06-30 15:20 ` Len Brown
2021-06-30 15:25 ` Enrico Weigelt, metux IT consult
2021-05-21 16:14 ` Dave Hansen
2021-05-21 16:19 ` Florian Weimer
2021-05-21 16:26 ` Len Brown
2021-05-21 16:28 ` Dave Hansen
2021-05-21 16:31 ` Andy Lutomirski
2021-05-21 19:10 ` Thomas Gleixner
2021-05-21 20:07 ` Andy Lutomirski
2021-05-21 21:43 ` Thomas Gleixner
2021-05-21 22:07 ` Len Brown
2021-05-21 22:46 ` Thomas Gleixner
2021-05-21 23:31 ` Len Brown
2021-05-22 7:16 ` Florian Weimer
2021-05-22 23:55 ` Andy Lutomirski
2021-05-21 23:06 ` Dave Hansen
2021-05-21 23:08 ` Len Brown
2021-05-21 19:05 ` Thomas Gleixner
2021-05-20 21:22 ` Len Brown
2021-05-20 21:41 ` Thomas Gleixner
2021-05-20 21:49 ` Len Brown
2021-05-21 9:26 ` Thomas Gleixner
2021-04-19 23:52 ` Paul Eggert
2021-04-13 20:16 ` Andy Lutomirski
2021-04-13 22:47 ` Len Brown
2021-04-13 22:58 ` Andy Lutomirski
2021-04-14 21:48 ` Len Brown
2021-04-15 16:24 ` Andy Lutomirski
2021-04-15 17:00 ` Dave Hansen
2021-04-15 17:38 ` Andy Lutomirski
2021-04-16 21:54 ` Len Brown
2021-04-16 22:03 ` Andy Lutomirski [this message]
2021-04-16 22:10 ` Len Brown
2021-04-16 22:14 ` Andy Lutomirski
2021-04-17 1:57 ` Len Brown
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