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authorSteven Rostedt <srostedt@redhat.com>2008-01-25 21:08:05 +0100
committerIngo Molnar <mingo@elte.hu>2008-01-25 21:08:05 +0100
commite8fa136262e1121288bb93befe2295928ffd240d (patch)
tree5df829adde9b43efee39275c05751c99bf46eb2f /kernel/sched.c
parent764a9d6fe4b52995c8aba277e3634385699354f4 (diff)
downloadlwn-e8fa136262e1121288bb93befe2295928ffd240d.tar.gz
lwn-e8fa136262e1121288bb93befe2295928ffd240d.zip
sched: add RT task pushing
This patch adds an algorithm to push extra RT tasks off a run queue to other CPU runqueues. When more than one RT task is added to a run queue, this algorithm takes an assertive approach to push the RT tasks that are not running onto other run queues that have lower priority. The way this works is that the highest RT task that is not running is looked at and we examine the runqueues on the CPUS for that tasks affinity mask. We find the runqueue with the lowest prio in the CPU affinity of the picked task, and if it is lower in prio than the picked task, we push the task onto that CPU runqueue. We continue pushing RT tasks off the current runqueue until we don't push any more. The algorithm stops when the next highest RT task can't preempt any other processes on other CPUS. TODO: The algorithm may stop when there are still RT tasks that can be migrated. Specifically, if the highest non running RT task CPU affinity is restricted to CPUs that are running higher priority tasks, there may be a lower priority task queued that has an affinity with a CPU that is running a lower priority task that it could be migrated to. This patch set does not address this issue. Note: checkpatch reveals two over 80 character instances. I'm not sure that breaking them up will help visually, so I left them as is. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 6185fa080ec8..97cab609fc31 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1952,6 +1952,8 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
prev_state = prev->state;
finish_arch_switch(prev);
finish_lock_switch(rq, prev);
+ schedule_tail_balance_rt(rq);
+
fire_sched_in_preempt_notifiers(current);
if (mm)
mmdrop(mm);
@@ -2185,11 +2187,13 @@ static void double_rq_unlock(struct rq *rq1, struct rq *rq2)
/*
* double_lock_balance - lock the busiest runqueue, this_rq is locked already.
*/
-static void double_lock_balance(struct rq *this_rq, struct rq *busiest)
+static int double_lock_balance(struct rq *this_rq, struct rq *busiest)
__releases(this_rq->lock)
__acquires(busiest->lock)
__acquires(this_rq->lock)
{
+ int ret = 0;
+
if (unlikely(!irqs_disabled())) {
/* printk() doesn't work good under rq->lock */
spin_unlock(&this_rq->lock);
@@ -2200,9 +2204,11 @@ static void double_lock_balance(struct rq *this_rq, struct rq *busiest)
spin_unlock(&this_rq->lock);
spin_lock(&busiest->lock);
spin_lock(&this_rq->lock);
+ ret = 1;
} else
spin_lock(&busiest->lock);
}
+ return ret;
}
/*