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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>
This commit is contained in:
Paul Turner 2010-11-15 15:47:04 -08:00 committed by Ingo Molnar
parent f0d7442a59
commit e33078baa4
2 changed files with 22 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
kernel/sched.c
View File

@ -355,7 +355,7 @@ struct cfs_rq {
u64 load_avg;
u64 load_period;
u64 load_stamp;
u64 load_stamp, load_last;
unsigned long load_contribution;
#endif

33
kernel/sched_fair.c
View File

@ -674,10 +674,11 @@ account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
}
#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 @@ static void update_cfs_load(struct cfs_rq *cfs_rq, int lb)
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 @@ static void update_cfs_load(struct cfs_rq *cfs_rq, int lb)
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 @@ static void update_cfs_shares(struct cfs_rq *cfs_rq, long weight_delta)
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 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
* 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 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
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 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
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 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
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 @@ static int tg_shares_up(struct task_group *tg, int cpu)
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;