tree eeef6ce3d48df86a7b2c1178a9ba54210b8b8981
parent 0a9ac38246b11892ad20a1eb9deb67adf8c0db2f
author Nick Piggin <npiggin@suse.de> 1171270431 -0800
committer Linus Torvalds <torvalds@woody.linux-foundation.org> 1171302517 -0800

[PATCH] sched: avoid div in rebalance_tick

Avoid expensive integer divide 3 times per CPU per tick.

A userspace test of this loop went from 26ns, down to 19ns on a G5; and
from 123ns down to 28ns on a P3.

(Also avoid a variable bit shift, as suggested by Alan. The effect
of this wasn't noticable on the CPUs I tested with).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>