Commit e4c2fb0d authored Jul 05, 2011 by Peter Zijlstra Committed by Ingo Molnar Jul 05, 2011

sched: Disable (revert) SCHED_LOAD_SCALE increase



Alex reported that commit c8b28116 ("sched: Increase
SCHED_LOAD_SCALE resolution") caused a power usage regression
under light load as it increases the number of load-balance
operations and keeps idle cpus from staying idle.

Time has run out to find the root cause for this release so
disable the feature for v3.0 until we can figure out what
causes the problem.

Reported-by: "Alex, Shi" <alex.shi@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nikhil Rao <ncrao@google.com>
Cc: Ming Lei <tom.leiming@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-m4onxn0sxnyn5iz9o88eskc3@git.kernel.org


Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent cd62287e

include/linux/sched.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -808,7 +808,7 @@ enum cpu_idle_type {
		* when BITS_PER_LONG <= 32 are pretty high and the returns do not justify the
		* increased costs.
		*/
		#if BITS_PER_LONG > 32
		#if 0 /* BITS_PER_LONG > 32 -- currently broken: it increases power usage under light load */
		# define SCHED_LOAD_RESOLUTION 10
		# define scale_load(w) ((w) << SCHED_LOAD_RESOLUTION)
		# define scale_load_down(w) ((w) >> SCHED_LOAD_RESOLUTION)