[patch] sched: fix sd_parent_degenerate on non-numa smp machine

From: Ken Chen
Date: Sun Dec 07 2008 - 21:48:00 EST

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@xxxxxxxxxx>

diff --git a/kernel/sched.c b/kernel/sched.c
index b7480fb..6beae36 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6814,6 +6814,8 @@ sd_parent_degenerate
+ if (nr_node_ids == 1)
+ pflags &= ~SD_SERIALIZE;
if (~cflags & pflags)
return 0;
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