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Subject: Re: [PATCH] likely cleanup: remove unlikely for kfree(NULL)
From: Arjan van de Ven <arjan@infradead.org>
To: Pekka J Enberg <penberg@cs.Helsinki.FI>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>,
       =?ISO-8859-1?Q?J=F6rn?= Engel <joern@wohnheim.fh-wedel.de>,
       Hua Zhong <hzhong@gmail.com>, linux-kernel@vger.kernel.org,
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Date: Thu, 27 Apr 2006 08:50:40 +0200
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On Thu, 2006-04-27 at 09:28 +0300, Pekka J Enberg wrote:
> On Thu, 27 Apr 2006, Nick Piggin wrote:
> > Not to dispute your conclusions or method, but I think doing a
> > defconfig or your personal config might be more representative
> > of % size increase of text that will actually be executed. And
> > that is the expensive type of text.
> 
> True but I was under the impression that Arjan thought we'd get text 
> savings with GCC 4.1 by making kfree() inline.

not savings in text size, I'll settle for the same size.
What we gain is less branches in the hotpath... eg a kfree that gets
optimized now has one less branch. Note that the branch predictor isn't
going to help you for these 100% cases, since the same branch "slot" is
shared between all callers; with this inline the branch predictor at
least gets to keep stats for each of the callers individually.
That is where the gain is....