From: David Laight <David.Laight@ACULAB.COM>
To: 'Nick Desaulniers' <ndesaulniers@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>
Cc: "x86@kernel.org" <x86@kernel.org>,
"H . Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Kees Cook <keescook@chromium.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
"llvm@lists.linux.dev" <llvm@lists.linux.dev>,
Andy Lutomirski <luto@kernel.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>
Subject: RE: [PATCH v4] x86, mem: move memmove to out of line assembler
Date: Fri, 30 Sep 2022 09:55:27 +0000 [thread overview]
Message-ID: <5672845ec66744df9ee0f0c56031ab00@AcuMS.aculab.com> (raw)
In-Reply-To: <20220928210512.642594-1-ndesaulniers@google.com>
From: Nick Desaulniers
> Sent: 28 September 2022 22:05
...
> memmove is quite large and probably shouldn't be inlined due to size
> alone
..
> + /* Decide forward/backward copy mode */
> + cmpl dest, src
> + jb .Lbackwards_header
It has to be better to do the slightly more complicated
test 'dest - src < size' (as unsigned) so that reverse
copies are only done when absolutely necessary.
Ignoring pathological cases on some cpu families the
forwards copy will benefit from hardware cache prefetch.
I also have a vague recollection of std and cld being slow.
Oh - and why do all the labels have 'byteswap' in them?
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2022-09-30 9:55 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-23 17:02 [PATCH] " Nick Desaulniers
2022-09-23 17:29 ` Linus Torvalds
2022-09-23 17:55 ` Nick Desaulniers
2022-09-23 18:05 ` Linus Torvalds
2022-09-27 17:03 ` Nick Desaulniers
2022-09-27 17:28 ` [PATCH v2] " Nick Desaulniers
2022-09-27 18:41 ` Kees Cook
2022-09-27 19:23 ` Kees Cook
2022-09-27 20:01 ` Nick Desaulniers
2022-09-27 20:36 ` Kees Cook
2022-09-27 21:02 ` [PATCH v3] " Nick Desaulniers
2022-09-27 21:14 ` Kees Cook
2022-09-28 7:24 ` Rasmus Villemoes
2022-09-28 19:00 ` Linus Torvalds
2022-09-28 19:06 ` Nick Desaulniers
2022-09-28 20:49 ` Nick Desaulniers
2022-09-28 21:05 ` [PATCH v4] " Nick Desaulniers
2022-09-28 22:03 ` Kees Cook
2022-09-29 7:01 ` Ingo Molnar
2022-09-29 8:02 ` Ingo Molnar
2022-09-29 17:26 ` Nick Desaulniers
2022-09-30 9:55 ` David Laight [this message]
2022-09-30 16:43 ` Nick Desaulniers
2022-09-30 16:46 ` Linus Torvalds
2022-09-30 18:55 ` [PATCH v5] " Nick Desaulniers
2022-09-30 10:14 ` [PATCH v4] " David Laight
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