Commit 5436499e authored Dec 07, 2008 by Ken Chen Committed by Ingo Molnar Dec 08, 2008

sched: fix sd_parent_degenerate on non-numa smp machine

Impact: optimize the sched domains tree some more

The addition of SD_SERIALIZE flag added to SD_NODE_INIT prevented top level
dummy numa sched_domain to be properly degenerated on non-numa smp machine.
The reason is that in sd_parent_degenerate(), it found that the child and
parent does not have comon sched_domain flags due to SD_SERIALIZE. However,
for non-numa smp box, the top level is a dummy with a single sched_group.

Filter out SD_SERIALIZE if it is on non-numa machine to properly degenerate
top level node sched_domain. this will cut back some of the sd domain walk
in the load balancer code.

Signed-off-by: Ken Chen <kenchen@google.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 4d117c5c

kernel/sched.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -6768,6 +6768,8 @@ sd_parent_degenerate(struct sched_domain sd, struct sched_domain parent)
		SD_BALANCE_EXEC \|
		SD_SHARE_CPUPOWER \|
		SD_SHARE_PKG_RESOURCES);
		if (nr_node_ids == 1)
		pflags &= ~SD_SERIALIZE;
		}
		if (~cflags & pflags)
		return 0;