All of lore.kernel.org
 help / color / mirror / Atom feed
From: David Laight <David.Laight@ACULAB.COM>
To: "'H. Peter Anvin'" <hpa@zytor.com>,
	'Linus Torvalds' <torvalds@linux-foundation.org>
Cc: Noah Goldstein <goldstein.w.n@gmail.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"oe-kbuild-all@lists.linux.dev" <oe-kbuild-all@lists.linux.dev>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"edumazet@google.com" <edumazet@google.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"bp@alien8.de" <bp@alien8.de>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>
Subject: RE: x86/csum: Remove unnecessary odd handling
Date: Sun, 7 Jan 2024 11:44:19 +0000	[thread overview]
Message-ID: <5dd4c01e4337455b9b2c0f5635d7f6f9@AcuMS.aculab.com> (raw)
In-Reply-To: <4313F9BB-DE2E-448F-A366-A68CAEA2BFE0@zytor.com>

From: H. Peter Anvin
> Sent: 07 January 2024 01:09
> 
> On January 6, 2024 2:08:48 PM PST, David Laight <David.Laight@ACULAB.COM> wrote:
...
> >The best loop for 256+ bytes is an adxc/adxo one.
> >However that requires the run-time patching.
...
> Rather than runtime patching perhaps separate paths...

It will need to detect the cpu type earlier, so a static
branch is probably enough.
Easier than substituting the entire code block.

I think it is silvermont and knight's landing that have
a 4 clock penalty for 64bit adxc (Intel atom family).
That might only be a decode penalty, so doesn't affect
the loop 'that much' (adc is 2 clocks on those cpu).
So probably not actually worth doing a run-time
performance check.

I might 'cook up' a full checksum function later.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

  reply	other threads:[~2024-01-07 11:44 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20230628020657.957880-1-goldstein.w.n@gmail.com>
2023-06-28  9:12 ` x86/csum: Remove unnecessary odd handling Borislav Petkov
2023-06-28 15:32   ` Noah Goldstein
2023-06-28 17:44     ` Linus Torvalds
2023-06-28 18:34       ` Noah Goldstein
2023-06-28 20:02         ` Linus Torvalds
2023-06-29 14:04   ` David Laight
2023-06-29 14:27   ` David Laight
2023-09-01 22:21 ` Noah Goldstein
2023-09-06 13:49   ` David Laight
2023-09-06 14:38   ` David Laight
2023-09-20 19:20     ` Noah Goldstein
2023-09-20 19:23 ` Noah Goldstein
2023-09-23  3:24   ` kernel test robot
2023-09-23 14:05     ` Noah Goldstein
2023-09-23 21:13       ` David Laight
2023-09-24 14:35         ` Noah Goldstein
2023-12-23 22:18           ` Noah Goldstein
2024-01-04 23:28             ` Noah Goldstein
2024-01-04 23:34               ` Dave Hansen
2024-01-04 23:36               ` Linus Torvalds
2024-01-05  0:33                 ` Linus Torvalds
2024-01-05 10:41                   ` David Laight
2024-01-05 16:12                     ` David Laight
2024-01-05 18:05                     ` Linus Torvalds
2024-01-05 23:52                       ` David Laight
2024-01-06  0:18                         ` Linus Torvalds
2024-01-06 10:26                           ` Eric Dumazet
2024-01-06 19:32                             ` Linus Torvalds
2024-01-07 12:11                             ` David Laight
2024-01-06 22:08                       ` David Laight
2024-01-07  1:09                         ` H. Peter Anvin
2024-01-07 11:44                           ` David Laight [this message]
2023-09-24 14:35 ` Noah Goldstein

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=5dd4c01e4337455b9b2c0f5635d7f6f9@AcuMS.aculab.com \
    --to=david.laight@aculab.com \
    --cc=bp@alien8.de \
    --cc=dave.hansen@linux.intel.com \
    --cc=edumazet@google.com \
    --cc=goldstein.w.n@gmail.com \
    --cc=hpa@zytor.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=oe-kbuild-all@lists.linux.dev \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.