Re: [PATCH] likely cleanup: remove unlikely for kfree(NULL)
From: Nick Piggin
Date: Thu Apr 27 2006 - 02:46:56 EST
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
Wouldn't it be better to simply remove calls to kfree() with known
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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