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authorEric Dumazet <eric.dumazet@gmail.com>2010-11-09 16:29:27 +0100
committerMichal Marek <mmarek@suse.cz>2010-11-11 17:12:06 +0100
commit8af27e1dc4e4dd7a7b04c2cd0fc3d419d91d45b0 (patch)
tree0cf6febb82aafa421259a69007a6e848c3b9fa3c /README
parentd63f6d1b4d3ad0d88685a5f8eb1c3cac01ddd0db (diff)
downloadlinux-8af27e1dc4e4dd7a7b04c2cd0fc3d419d91d45b0.tar.gz
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>
Diffstat (limited to 'README')
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