Commit cb0b9f24 authored Nov 05, 2014 by Wanpeng Li Committed by Ingo Molnar Nov 16, 2014

sched/fair: Fix stale overloaded status in the busiest group finding logic



Commit caeb178c ("sched/fair: Make update_sd_pick_busiest() return
'true' on a busier sd") changes groups to be ranked in the order of
overloaded > imbalance > other, and busiest group is picked according
to this order.

sgs->group_capacity_factor is used to check if the group is overloaded.

When the child domain prefers tasks to go to siblings first, the
sgs->group_capacity_factor will be set lower than one in order to
move all the excess tasks away.

However, group overloaded status is not updated when
sgs->group_capacity_factor is set to lower than one, which leads to us
missing to find the busiest group.

This patch fixes it by updating group overloaded status when sg capacity
factor is set to one, in order to find the busiest group accurately.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Kirill Tkhai <ktkhai@parallels.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1415144690-25196-1-git-send-email-wanpeng.li@linux.intel.com


[ Fixed the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 6c1d9410

kernel/sched/fair.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -6352,8 +6352,10 @@ static inline void update_sd_lb_stats(struct lb_env env, struct sd_lb_stats sd
		* with a large weight task outweighs the tasks on the system).
		*/
		if (prefer_sibling && sds->local &&
		sds->local_stat.group_has_free_capacity)
		sds->local_stat.group_has_free_capacity) {
		sgs->group_capacity_factor = min(sgs->group_capacity_factor, 1U);
		sgs->group_type = group_classify(sg, sgs);
		}

		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
		sds->busiest = sg;

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