From 7268a6ed3ef712831a3f11a409e81ec68675fea0 Mon Sep 17 00:00:00 2001 From: Mike Galbraith Date: Mon, 11 Aug 2008 13:32:02 +0200 Subject: [PATCH] sched: fix mysql+oltp regression Defer commit 552ac5ae946b3db6ce1900fa8e3df4355b20e599 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 10c3758 9646 17876 34774 33868 32230 30767 29441 2.6.26.1 9112 17936 34652 33383 31929 30665 29232 552ac5a 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 Acked-by: Peter Zijlstra Cc: Gregory Haskins Signed-off-by: Ingo Molnar --- kernel/sched_fair.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 0fe94ea43f325..fb8994c6d4bb4 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -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; } -- 2.39.5