Commit 77ae6513 authored Aug 11, 2008 by Mike Galbraith Committed by Ingo Molnar Aug 11, 2008

sched: fix mysql+oltp regression



Defer commit 6d299f1b to the next release.

Testing of the tip/sched/clock tree revealed a mysql+oltp regression
which bisection eventually traced back to this commit in mainline.

Pertinent test results:  Three run sysbench averages, throughput units
in read/write requests/sec.

clients         1     2     4     8    16    32    64
6e0534f2      9646 17876 34774 33868 32230 30767 29441
2.6.26.1     9112 17936 34652 33383 31929 30665 29232
6d299f1b      9112 14637 28370 33339 32038 30762 29204

Note: subsequent commits hide the majority of this regression until you
apply the clock fixes, at which time it reemerges at full magnitude.

We cannot see anything bad about the change itself so we defer it to the
next release until this problem is fully analysed.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 251a169c

kernel/sched_fair.c

+12 −7

Original line number	Diff line number	Diff line
		@@ -1442,18 +1442,23 @@ __load_balance_iterator(struct cfs_rq cfs_rq, struct list_head next)
		struct task_struct *p = NULL;
		struct sched_entity *se;

		while (next != &cfs_rq->tasks) {
		if (next == &cfs_rq->tasks)
		return NULL;

		/* Skip over entities that are not tasks */
		do {
		se = list_entry(next, struct sched_entity, group_node);
		next = next->next;
		} while (next != &cfs_rq->tasks && !entity_is_task(se));

		/* Skip over entities that are not tasks */
		if (entity_is_task(se)) {
		p = task_of(se);
		break;
		}
		}
		if (next == &cfs_rq->tasks)
		return NULL;

		cfs_rq->balance_iterator = next;

		if (entity_is_task(se))
		p = task_of(se);

		return p;
		}

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