Re: [PATCH] likely cleanup: remove unlikely for kfree(NULL)

[Nick Piggin <nickpiggin@yahoo.com.au>]

Pekka J Enberg wrote:
> On Wed, 26 Apr 2006, Kyle Moffett wrote:
>
> > Here's code that I've found works as well as can be expected under both GCC 3
> > and GCC 4.  If xp is a known-NULL constant the whole function will be
> > optimized out completely.  If xp is known-not-NULL, then it will optimize to a
> > kfree function without the null check.  Otherwise it optimizes to call the
> > out-of-line version.
>
>
> Wouldn't it be better to simply remove calls to kfree() with known 
> NULL constant?

Yes, but this will optimise away the check for known non-NULL.

At the cost of icache footprint.

I think unmeasurable micro-optimisations that go against historic
CPU trends (eg. size for speed) aren't worth wasting too much
sleep over. If it is a 0.0001% speedup today, it'll be a 0.0001%
slowdown tomorrow :)

--
SUSE Labs, Novell Inc.
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