From: Al Viro <viro@zeniv.linux.org.uk>
To: David Laight <David.Laight@aculab.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
Subject: Re: [PATCH 04/18] csum_and_copy_..._user(): pass 0xffffffff instead of 0 as initial sum
Date: Wed, 22 Jul 2020 16:54:52 +0100 [thread overview]
Message-ID: <20200722155452.GF2786714@ZenIV.linux.org.uk> (raw)
In-Reply-To: <4e03cce8ed184d40bb0ea40fd3d51000@AcuMS.aculab.com>
On Wed, Jul 22, 2020 at 03:22:45PM +0000, David Laight wrote:
> > And the benefit of that would be...? It wouldn't be any simpler,
> > it almost certainly would not even be a valid microoptimization
> > (nevermind that this is an arch-independent code)...
>
> It ought to give a minor improvement because it saves the extra
> csum_fold() when the checksum from a buffer is added to the
> previous total.
>
Sigh... _WHAT_ csum_fold()?
static inline __wsum
csum_block_add(__wsum csum, __wsum csum2, int offset)
{
u32 sum = (__force u32)csum2;
/* rotate sum to align it with a 16b boundary */
if (offset & 1)
sum = ror32(sum, 8);
return csum_add(csum, (__force __wsum)sum);
}
David, do you *ever* bother to RTFS? I mean, competent supercilious twits
are annoying, but at least with those you can generally assume that what
they say makes sense and has some relation to reality. You, OTOH, keep
spewing utter bollocks, without ever lowering yourself to checking if your
guesses have anything to do with the reality. With supercilious twit part
proudly on the display - you do speak with confidence, and the way you
dispense the oh-so-valuable advice to everyone around...
next prev parent reply other threads:[~2020-07-22 15:54 UTC|newest]
Thread overview: 102+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-21 20:24 [RFC][CFT][PATCHSET] saner calling conventions for csum-and-copy primitives Al Viro
2020-07-21 20:25 ` [PATCH 01/18] skb_copy_and_csum_bits(): don't bother with the last argument Al Viro
2020-07-21 20:25 ` [PATCH 02/18] icmp_push_reply(): reorder adding the checksum up Al Viro
2020-07-21 20:25 ` [PATCH 03/18] csum_partial_copy_nocheck(): drop the last argument Al Viro
2020-07-21 20:25 ` Al Viro
2020-07-21 20:25 ` [PATCH 04/18] csum_and_copy_..._user(): pass 0xffffffff instead of 0 as initial sum Al Viro
2020-07-21 20:25 ` Al Viro
2020-07-21 20:55 ` Linus Torvalds
2020-07-21 20:58 ` Linus Torvalds
2020-07-21 21:11 ` Al Viro
2020-07-21 21:16 ` Linus Torvalds
2020-07-21 21:16 ` Linus Torvalds
2020-07-25 17:54 ` Al Viro
2020-07-22 9:45 ` David Laight
2020-07-22 9:27 ` David Laight
2020-07-22 14:42 ` Al Viro
2020-07-22 15:22 ` David Laight
2020-07-22 15:54 ` Al Viro [this message]
2020-07-22 16:17 ` David Laight
2020-07-22 17:39 ` Al Viro
2020-07-23 8:29 ` David Laight
2020-07-23 13:54 ` David Laight
2020-07-23 14:30 ` David Laight
2020-07-23 14:53 ` Al Viro
2020-07-23 15:19 ` David Laight
2020-07-23 15:21 ` Al Viro
2020-07-23 15:36 ` David Laight
2020-07-21 20:25 ` [PATCH 05/18] saner calling conventions for csum_and_copy_..._user() Al Viro
2020-07-21 20:25 ` Al Viro
2020-07-21 20:25 ` [PATCH 06/18] alpha: propagate the calling convention changes down to csum_partial_copy.c helpers Al Viro
2020-07-21 20:25 ` Al Viro
2020-07-21 20:25 ` [PATCH 07/18] arm: propagate the calling convention changes down to csum_partial_copy_from_user() Al Viro
2020-07-21 20:25 ` [PATCH 08/18] m68k: get rid of zeroing destination on error in csum_and_copy_from_user() Al Viro
2020-07-21 20:25 ` Al Viro
2020-07-21 20:25 ` [PATCH 09/18] sh: propage the calling conventions change down to csum_partial_copy_generic() Al Viro
2020-07-21 20:25 ` [PATCH 10/18] i386: propagate " Al Viro
2020-07-21 20:25 ` Al Viro
2020-07-21 20:25 ` [PATCH 11/18] sparc32: propagate the calling conventions change down to __csum_partial_copy_sparc_generic() Al Viro
2020-07-21 20:25 ` Al Viro
2020-07-22 1:20 ` David Miller
2020-07-21 20:25 ` [PATCH 12/18] mips: csum_and_copy_{to,from}_user() are never called under KERNEL_DS Al Viro
2020-07-21 20:25 ` [PATCH 13/18] mips: __csum_partial_copy_kernel() has no users left Al Viro
2020-07-21 20:25 ` Al Viro
2020-07-21 20:25 ` [PATCH 14/18] mips: propagate the calling convention change down into __csum_partial_copy_..._user() Al Viro
2020-07-21 20:25 ` Al Viro
2020-07-21 20:25 ` [PATCH 15/18] xtensa: propagate the calling conventions change down into csum_partial_copy_generic() Al Viro
2020-07-22 8:56 ` Max Filippov
2020-07-21 20:25 ` [PATCH 16/18] sparc64: propagate the calling convention changes down to __csum_partial_copy_...() Al Viro
2020-07-21 20:25 ` Al Viro
2020-07-22 1:21 ` David Miller
2020-07-21 20:25 ` [PATCH 17/18] amd64: switch csum_partial_copy_generic() to new calling conventions Al Viro
2020-07-21 20:25 ` Al Viro
2020-07-21 20:25 ` [PATCH 18/18] ppc: propagate the calling conventions change down to csum_partial_copy_generic() Al Viro
2020-07-21 20:25 ` Al Viro
2020-07-24 1:25 ` [RFC][CFT][PATCHSET v2] saner calling conventions for csum-and-copy primitives Al Viro
2020-07-24 1:25 ` [PATCH v2 01/20] xtensa: fix access check in csum_and_copy_from_user Al Viro
2020-07-24 1:25 ` [PATCH v2 02/20] skb_copy_and_csum_bits(): don't bother with the last argument Al Viro
2020-07-24 1:25 ` [PATCH v2 03/20] icmp_push_reply(): reorder adding the checksum up Al Viro
2020-07-24 1:25 ` Al Viro
2020-07-24 1:25 ` [PATCH v2 04/20] unify generic instances of csum_partial_copy_nocheck() Al Viro
2020-07-24 6:41 ` Christoph Hellwig
2020-07-24 12:19 ` Al Viro
2020-07-24 12:23 ` Christoph Hellwig
2020-07-24 12:30 ` Al Viro
2020-07-26 7:11 ` Christoph Hellwig
2020-07-26 7:11 ` Christoph Hellwig
2020-07-27 3:58 ` Al Viro
2020-07-24 1:25 ` [PATCH v2 05/20] csum_partial_copy_nocheck(): drop the last argument Al Viro
2020-07-24 1:25 ` Al Viro
2020-07-24 1:25 ` [PATCH v2 06/20] csum_and_copy_..._user(): pass 0xffffffff instead of 0 as initial sum Al Viro
2020-07-24 1:25 ` [PATCH v2 07/20] saner calling conventions for csum_and_copy_..._user() Al Viro
2020-07-24 1:25 ` Al Viro
2020-07-24 1:25 ` [PATCH v2 08/20] alpha: propagate the calling convention changes down to csum_partial_copy.c helpers Al Viro
2020-07-24 1:25 ` Al Viro
2020-07-24 1:25 ` [PATCH v2 09/20] arm: propagate the calling convention changes down to csum_partial_copy_from_user() Al Viro
2020-07-24 1:25 ` [PATCH v2 10/20] m68k: get rid of zeroing destination on error in csum_and_copy_from_user() Al Viro
2020-07-24 1:25 ` [PATCH v2 11/20] sh: propage the calling conventions change down to csum_partial_copy_generic() Al Viro
2020-07-24 1:25 ` Al Viro
2020-07-24 1:25 ` [PATCH v2 12/20] i386: propagate " Al Viro
2020-07-24 1:25 ` [PATCH v2 13/20] sparc32: propagate the calling conventions change down to __csum_partial_copy_sparc_generic() Al Viro
2020-07-24 1:25 ` Al Viro
2020-07-24 1:25 ` [PATCH v2 14/20] mips: csum_and_copy_{to,from}_user() are never called under KERNEL_DS Al Viro
2020-07-24 1:25 ` [PATCH v2 15/20] mips: __csum_partial_copy_kernel() has no users left Al Viro
2020-07-24 1:25 ` Al Viro
2020-07-24 1:25 ` [PATCH v2 16/20] mips: propagate the calling convention change down into __csum_partial_copy_..._user() Al Viro
2020-07-24 1:25 ` Al Viro
2020-07-24 1:25 ` [PATCH v2 17/20] xtensa: propagate the calling conventions change down into csum_partial_copy_generic() Al Viro
2020-07-24 1:25 ` Al Viro
2020-07-24 1:25 ` [PATCH v2 18/20] sparc64: propagate the calling convention changes down to __csum_partial_copy_...() Al Viro
2020-07-24 1:25 ` Al Viro
2020-07-24 1:25 ` [PATCH v2 19/20] amd64: switch csum_partial_copy_generic() to new calling conventions Al Viro
2020-07-24 1:25 ` Al Viro
2020-07-24 1:25 ` [PATCH v2 20/20] ppc: propagate the calling conventions change down to csum_partial_copy_generic() Al Viro
2020-07-24 1:25 ` Al Viro
2020-10-14 22:26 ` Jason A. Donenfeld
2020-10-14 22:51 ` Linus Torvalds
2020-10-14 22:53 ` Linus Torvalds
2020-10-14 22:54 ` Jason A. Donenfeld
2020-10-14 22:53 ` Jason A. Donenfeld
2020-10-14 23:12 ` Al Viro
2020-10-14 23:02 ` [PATCH] powerpc32: don't adjust unmoved stack pointer in csum_partial_copy_generic() epilogue Jason A. Donenfeld
2020-10-14 23:05 ` Linus Torvalds
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