sched: new task placement for vruntime
add proper new task placement for the vruntime based math too.
( note: introduces a swap() macro, but the swap token is too
widely used in the kernel namespace for a generic version
to be added without changing non-scheduler code - so this
cleanup will be done separately. )
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 7041dc6..95487e3 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -203,6 +203,20 @@
* Scheduling class statistics methods:
*/
+static u64 __sched_period(unsigned long nr_running)
+{
+ u64 period = sysctl_sched_latency;
+ unsigned long nr_latency =
+ sysctl_sched_latency / sysctl_sched_min_granularity;
+
+ if (unlikely(nr_running > nr_latency)) {
+ period *= nr_running;
+ do_div(period, nr_latency);
+ }
+
+ return period;
+}
+
/*
* Calculate the preemption granularity needed to schedule every
* runnable task once per sysctl_sched_latency amount of time.
@@ -1103,6 +1117,8 @@
}
}
+#define swap(a,b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0)
+
/*
* Share the fairness runtime between parent and child, thus the
* total amount of pressure for CPU stays equal - new tasks
@@ -1118,14 +1134,9 @@
sched_info_queued(p);
update_curr(cfs_rq);
+ se->vruntime = cfs_rq->min_vruntime;
update_stats_enqueue(cfs_rq, se);
- /*
- * Child runs first: we let it run before the parent
- * until it reschedules once. We set up the key so that
- * it will preempt the parent:
- */
- se->fair_key = curr->fair_key -
- niced_granularity(curr, sched_granularity(cfs_rq)) - 1;
+
/*
* The first wait is dominated by the child-runs-first logic,
* so do not credit it with that waiting time yet:
@@ -1138,9 +1149,16 @@
* -granularity/2, so initialize the task with that:
*/
if (sched_feat(START_DEBIT))
- se->wait_runtime = -(sched_granularity(cfs_rq) / 2);
+ se->wait_runtime = -(__sched_period(cfs_rq->nr_running+1) / 2);
- se->vruntime = cfs_rq->min_vruntime;
+ if (sysctl_sched_child_runs_first &&
+ curr->vruntime < se->vruntime) {
+
+ dequeue_entity(cfs_rq, curr, 0);
+ swap(curr->vruntime, se->vruntime);
+ enqueue_entity(cfs_rq, curr, 0);
+ }
+
update_stats_enqueue(cfs_rq, se);
__enqueue_entity(cfs_rq, se);
resched_task(rq->curr);