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From: Arjan van de Ven <arjan@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Luiz Fernando N. Capitulino" <lcapitulino@mandriva.com.br>,
linux-kernel@vger.kernel.org
Subject: Re: PATCH: __bprm_mm_init(): remove uneeded goto
Date: Tue, 4 Nov 2008 18:48:54 -0800 [thread overview]
Message-ID: <20081104184854.72044220@infradead.org> (raw)
In-Reply-To: <20081104114703.c950f078.akpm@linux-foundation.org>
On Tue, 4 Nov 2008 11:47:03 -0800
Andrew Morton <akpm@linux-foundation.org> wrote:
> We used to do this trick a *lot* in the kernel (back in the 2.2 days?)
> for this performance reason. Nowdays gcc is a lot more complex and we
> hope that it can sometimes work these things out for itself and we
> hope that `unlikely' might cause the compiler to move the unlikely
> code out of line. But I don't know how successful the compiler is at
> doing this, and it'll be dependent upon the gcc version, the wind
> direction, etc.
>
as far as I know, gcc tends to consider NULL pointer checks as unlikely
by default.
(but we can always tell it so if we think we know better..)
--
Arjan van de Ven Intel Open Source Technology Centre
For development, discussion and tips for power savings,
visit http://www.lesswatts.org
prev parent reply other threads:[~2008-11-05 2:48 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-04 16:03 Luiz Fernando N. Capitulino
2008-11-04 18:57 ` Andrew Morton
2008-11-04 19:14 ` Luiz Fernando N. Capitulino
2008-11-04 19:47 ` Andrew Morton
2008-11-05 2:48 ` Arjan van de Ven [this message]
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