sched: Fix update_cfs_load() synchronization
Using cfs_rq->nr_running is not sufficient to synchronize update_cfs_load with
the put path since nr_running accounting occurs at deactivation.
It's also not safe to make the removal decision based on load_avg as this fails
with both high periods and low shares. Resolve this by clipping history after
4 periods without activity.
Note: the above will always occur from update_shares() since in the
last-task-sleep-case that task will still be cfs_rq->curr when update_cfs_load
is called.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101115234937.933428187@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index d52b97a..a543a5b 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -674,10 +674,11 @@
}
#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
-static void update_cfs_load(struct cfs_rq *cfs_rq, int lb)
+static void update_cfs_load(struct cfs_rq *cfs_rq)
{
u64 period = sched_avg_period();
u64 now, delta;
+ unsigned long load = cfs_rq->load.weight;
if (!cfs_rq)
return;
@@ -685,9 +686,19 @@
now = rq_of(cfs_rq)->clock;
delta = now - cfs_rq->load_stamp;
+ /* truncate load history at 4 idle periods */
+ if (cfs_rq->load_stamp > cfs_rq->load_last &&
+ now - cfs_rq->load_last > 4 * period) {
+ cfs_rq->load_period = 0;
+ cfs_rq->load_avg = 0;
+ }
+
cfs_rq->load_stamp = now;
cfs_rq->load_period += delta;
- cfs_rq->load_avg += delta * cfs_rq->load.weight;
+ if (load) {
+ cfs_rq->load_last = now;
+ cfs_rq->load_avg += delta * load;
+ }
while (cfs_rq->load_period > period) {
/*
@@ -700,10 +711,8 @@
cfs_rq->load_avg /= 2;
}
- if (lb && !cfs_rq->nr_running) {
- if (cfs_rq->load_avg < (period / 8))
- list_del_leaf_cfs_rq(cfs_rq);
- }
+ if (!cfs_rq->curr && !cfs_rq->nr_running && !cfs_rq->load_avg)
+ list_del_leaf_cfs_rq(cfs_rq);
}
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
@@ -750,7 +759,7 @@
reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
-static inline void update_cfs_load(struct cfs_rq *cfs_rq, int lb)
+static inline void update_cfs_load(struct cfs_rq *cfs_rq)
{
}
@@ -880,7 +889,7 @@
* Update run-time statistics of the 'current'.
*/
update_curr(cfs_rq);
- update_cfs_load(cfs_rq, 0);
+ update_cfs_load(cfs_rq);
update_cfs_shares(cfs_rq, se->load.weight);
account_entity_enqueue(cfs_rq, se);
@@ -941,7 +950,7 @@
if (se != cfs_rq->curr)
__dequeue_entity(cfs_rq, se);
se->on_rq = 0;
- update_cfs_load(cfs_rq, 0);
+ update_cfs_load(cfs_rq);
account_entity_dequeue(cfs_rq, se);
update_min_vruntime(cfs_rq);
update_cfs_shares(cfs_rq, 0);
@@ -1176,7 +1185,7 @@
for_each_sched_entity(se) {
struct cfs_rq *cfs_rq = cfs_rq_of(se);
- update_cfs_load(cfs_rq, 0);
+ update_cfs_load(cfs_rq);
update_cfs_shares(cfs_rq, 0);
}
@@ -1206,7 +1215,7 @@
for_each_sched_entity(se) {
struct cfs_rq *cfs_rq = cfs_rq_of(se);
- update_cfs_load(cfs_rq, 0);
+ update_cfs_load(cfs_rq);
update_cfs_shares(cfs_rq, 0);
}
@@ -2023,7 +2032,7 @@
raw_spin_lock_irqsave(&rq->lock, flags);
update_rq_clock(rq);
- update_cfs_load(cfs_rq, 1);
+ update_cfs_load(cfs_rq);
load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1);
load_avg -= cfs_rq->load_contribution;