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authorShawn Bohrer <sbohrer@rgmadvisors.com>2011-09-12 09:28:04 -0500
committerIngo Molnar <mingo@elte.hu>2011-09-18 13:48:56 +0200
commit3be209a8e22cedafc1b6945608b7bb8d9887ab61 (patch)
tree643b1083f8863cbdb45b7e2375368391f6bc3486 /kernel
parent003f6c9df54970d8b19578d195b3e2b398cdbde2 (diff)
downloadlinux-linaro-precise-3be209a8e22cedafc1b6945608b7bb8d9887ab61.tar.gz
sched/rt: Migrate equal priority tasks to available CPUs
Commit 43fa5460fe60dea5c610490a1d263415419c60f6 ("sched: Try not to migrate higher priority RT tasks") also introduced a change in behavior which keeps RT tasks on the same CPU if there is an equal priority RT task currently running even if there are empty CPUs available. This can cause unnecessary wakeup latencies, and can prevent the scheduler from balancing all RT tasks across available CPUs. This change causes an RT task to search for a new CPU if an equal priority RT task is already running on wakeup. Lower priority tasks will still have to wait on higher priority tasks, but the system should still balance out because there is always the possibility that if there are both a high and low priority RT tasks on a given CPU that the high priority task could wakeup while the low priority task is running and force it to search for a better runqueue. Signed-off-by: Shawn Bohrer <sbohrer@rgmadvisors.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Tested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: stable@kernel.org # 37+ Link: http://lkml.kernel.org/r/1315837684-18733-1-git-send-email-sbohrer@rgmadvisors.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched_rt.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 97540f0c9e4..af1177858be 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -1050,7 +1050,7 @@ select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)
*/
if (curr && unlikely(rt_task(curr)) &&
(curr->rt.nr_cpus_allowed < 2 ||
- curr->prio < p->prio) &&
+ curr->prio <= p->prio) &&
(p->rt.nr_cpus_allowed > 1)) {
int target = find_lowest_rq(p);
@@ -1581,7 +1581,7 @@ static void task_woken_rt(struct rq *rq, struct task_struct *p)
p->rt.nr_cpus_allowed > 1 &&
rt_task(rq->curr) &&
(rq->curr->rt.nr_cpus_allowed < 2 ||
- rq->curr->prio < p->prio))
+ rq->curr->prio <= p->prio))
push_rt_tasks(rq);
}