LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: David Laight <David.Laight@ACULAB.COM>
To: 'Noah Goldstein' <goldstein.w.n@gmail.com>
Cc: "tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"bp@alien8.de" <bp@alien8.de>, "x86@kernel.org" <x86@kernel.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"luto@kernel.org" <luto@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v4] arch/x86: Improve 'rep movs{b|q}' usage in memmove_64.S
Date: Wed, 17 Nov 2021 22:31:21 +0000 [thread overview]
Message-ID: <bc0297a1b97a4b129fa3ea1b155f6062@AcuMS.aculab.com> (raw)
In-Reply-To: <20211117210245.843374-1-goldstein.w.n@gmail.com>
From: Noah Goldstein
> Sent: 17 November 2021 21:03
>
> Add check for "short distance movsb" for forwards FSRM usage and
> entirely remove backwards 'rep movsq'. Both of these usages hit "slow
> modes" that are an order of magnitude slower than usual.
>
> 'rep movsb' has some noticeable VERY slow modes that the current
> implementation is either 1) not checking for or 2) intentionally
> using.
How does this relate to the decision that glibc made a few years
ago to use backwards 'rep movs' for non-overlapping copies?
Did they find a different corner case??
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2021-11-17 22:31 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-01 4:49 [PATCH v1] arch/x86: Improve 'rep movs{b|q}' usage in memmove_64.S Noah Goldstein
2021-11-01 18:59 ` [PATCH v2] " Noah Goldstein
2021-11-02 23:15 ` [PATCH v3] " Noah Goldstein
2021-11-17 21:02 ` [PATCH v4] " Noah Goldstein
2021-11-17 22:31 ` David Laight [this message]
2021-11-17 22:45 ` Noah Goldstein
2021-11-19 22:31 ` David Laight
2021-11-20 0:05 ` Noah Goldstein
2021-12-10 18:35 ` Noah Goldstein
2022-01-12 3:13 ` Noah Goldstein
2022-02-10 9:08 ` Noah Goldstein
2022-03-16 14:15 ` Noah Goldstein
2022-03-16 16:23 ` Borislav Petkov
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=bc0297a1b97a4b129fa3ea1b155f6062@AcuMS.aculab.com \
--to=david.laight@aculab.com \
--cc=bp@alien8.de \
--cc=goldstein.w.n@gmail.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=tglx@linutronix.de \
--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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).