From: David Laight <David.Laight@ACULAB.COM>
To: 'Theodore Ts'o' <tytso@mit.edu>, Yangtao Li <frank.li@vivo.com>
Cc: "adilger.kernel@dilger.ca" <adilger.kernel@dilger.ca>,
"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>
Subject: RE: [PATCH] ext4: convert to DIV_ROUND_UP() in mpage_process_page_bufs()
Date: Mon, 13 Mar 2023 09:25:20 +0000 [thread overview]
Message-ID: <6135e1e118724e5ea3a1f7640b705cb5@AcuMS.aculab.com> (raw)
In-Reply-To: <20230310232107.GE860405@mit.edu>
...
> On 32-bit platforms --- i386 in particular --- the 64-bit division
> results in an out-of-line call to a helper function that is not
> supplied in the kernel compilation environment, so not only is it
> slower, it Just Doesn't Work.
Even on some 64-bit systems a 64bit divide can be significantly
slower than a 32-bit divide - even with the same arguments.
IIRC Intel x86-64 a 64-bit divide (128-bit dividend) is about
twice the clocks of a 32-bit one. On AMD cpu they are much the same.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
prev parent reply other threads:[~2023-03-13 9:25 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-10 6:07 [PATCH] ext4: convert to DIV_ROUND_UP() in mpage_process_page_bufs() Yangtao Li
2023-03-10 6:17 ` Eric Biggers
2023-03-10 6:27 ` Yangtao Li
2023-03-10 6:35 ` Gao Xiang
2023-03-10 6:37 ` Gao Xiang
2023-03-10 6:41 ` Eric Biggers
2023-03-10 6:37 ` Al Viro
2023-03-10 6:43 ` Al Viro
2023-03-10 6:43 ` Eric Biggers
2023-03-10 6:46 ` Al Viro
2023-03-10 6:54 ` Eric Biggers
2023-03-10 7:05 ` Al Viro
2023-03-10 7:12 ` Al Viro
2023-03-10 21:47 ` Eric Biggers
2023-03-10 19:07 ` kernel test robot
2023-03-10 19:38 ` kernel test robot
2023-03-10 23:21 ` Theodore Ts'o
2023-03-13 9:25 ` David Laight [this message]
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