From: "Pekka Enberg" <penberg@cs.helsinki.fi>
To: "Oliver Neukum" <oliver@neukum.org>
Cc: "Arjan van de Ven" <arjan@infradead.org>,
"Matthew Wilcox" <matthew@wil.cx>,
viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH]use kzalloc in vfs where appropriate
Date: Mon, 20 Mar 2006 09:25:06 +0200 [thread overview]
Message-ID: <84144f020603192325h54fd3212l1f4846fd40b9f074@mail.gmail.com> (raw)
In-Reply-To: <200603192150.23444.oliver@neukum.org>
Hi Oliver,
On 3/19/06, Oliver Neukum <oliver@neukum.org> wrote:
> Yes it is. The generated code is identical. But on second thought this is still
> not optimal. A full division is generated:
>
> xorl %edx, %edx
> movl $2147483647, %eax
> movq $0, 40(%rsp)
> divq %rcx
> movl $8, %edx
> cmpq %rax, %rdx
> ja .L313
>
> Rewriting the test as:
> n!=0 && n > INT_MAX / size
> saves the division because size is much likelier to be a constant, and indeed
> the code is better:
>
> cmpq $268435455, %rax
> movq $0, 40(%rsp)
> ja .L313
>
> Is there anything I am missing?
Did you check allyesconfig vmlinux size before and after? If it helps,
like it probably does, post a patch!
Pekka
next prev parent reply other threads:[~2006-03-20 7:25 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-17 20:58 [PATCH]use kzalloc in vfs where appropriate Oliver Neukum
2006-03-17 21:08 ` Matthew Wilcox
2006-03-18 10:44 ` Oliver Neukum
2006-03-18 10:55 ` Arjan van de Ven
2006-03-19 13:29 ` Oliver Neukum
2006-03-19 16:09 ` Arjan van de Ven
2006-03-19 20:50 ` Oliver Neukum
2006-03-20 7:25 ` Pekka Enberg [this message]
2006-03-20 12:52 ` Oliver Neukum
2006-03-20 13:08 ` Denis Vlasenko
2006-03-20 13:14 ` Oliver Neukum
2006-03-20 13:23 ` Pekka J Enberg
2006-03-20 13:16 ` Pekka J Enberg
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