linux-kernel - Re: PATCH: __bprm_mm_init(): remove uneeded goto

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Date:	Tue, 4 Nov 2008 18:48:54 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Luiz Fernando N. Capitulino" <lcapitulino@...driva.com.br>,
	linux-kernel@...r.kernel.org
Subject: Re: PATCH: __bprm_mm_init(): remove uneeded goto

On Tue, 4 Nov 2008 11:47:03 -0800
Andrew Morton <akpm@...ux-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
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