From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 9 Nov 2010 15:29:27 +0000 (+0100)
Subject: fixdep: use hash table instead of a single array
X-Git-Tag: v2.6.38-rc1~440^2~14
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8af27e1dc4e4dd7a7b04c2cd0fc3d419d91d45b0;p=pandora-kernel.git

fixdep: use hash table instead of a single array

I noticed fixdep uses ~2% of cpu time in kernel build, in function
use_config()

fixdep spends a lot of cpu cycles in linear searches in its internal
string array. With about 400 stored strings per dep file, this begins to
be noticeable.

Convert fixdep to use a hash table.

kbuild results on my x86_64 allmodconfig

Before patch :

real	10m30.414s
user	61m51.456s
sys	8m28.200s

real	10m12.334s
user	61m50.236s
sys	8m30.448s

real	10m42.947s
user	61m50.028s
sys	8m32.380s

After:

real	10m8.180s
user	61m22.506s
sys	8m32.384s

real	10m35.039s
user	61m21.654s
sys	8m32.212s

real	10m14.487s
user	61m23.498s
sys	8m32.312s

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
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