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Subject[PATCH v10 6/7] sched: Provide runnable_load_avg back to cfs_rq
Date
The cfs_rq's load_avg is composed of runnable_load_avg and blocked_load_avg.
Before this series, sometimes the runnable_load_avg is used, and sometimes
the load_avg is used. Completely replacing all uses of runnable_load_avg
with load_avg may be too big a leap, i.e., the blocked_load_avg is concerned
to result in overrated load. Therefore, we get runnable_load_avg back.

The new cfs_rq's runnable_load_avg is improved to be updated with all of the
runnable sched_eneities at the same time, so the one sched_entity updated and
the others stale problem is solved.

Signed-off-by: Yuyang Du <yuyang.du@intel.com>
---
kernel/sched/debug.c | 2 ++
kernel/sched/fair.c | 57 +++++++++++++++++++++++++++++++++++++++++-----------
kernel/sched/sched.h | 2 ++
3 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 56d83f3..bfb7bb2 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -205,6 +205,8 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
#ifdef CONFIG_SMP
SEQ_printf(m, " .%-30s: %lu\n", "load_avg",
cfs_rq->avg.load_avg);
+ SEQ_printf(m, " .%-30s: %lu\n", "runnable_load_avg",
+ cfs_rq->runnable_load_avg);
SEQ_printf(m, " .%-30s: %lu\n", "util_avg",
cfs_rq->avg.util_avg);
SEQ_printf(m, " .%-30s: %ld\n", "removed_load_avg",
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 19f1199..a1bffe1 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2545,9 +2545,9 @@ static u32 __compute_runnable_contrib(u64 n)
* = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
*/
static __always_inline int __update_load_avg(u64 now, int cpu,
- struct sched_avg *sa,
- unsigned long weight,
- int running)
+ struct sched_avg *sa,
+ unsigned long weight,
+ int running, struct cfs_rq *cfs_rq)
{
u64 delta, periods;
u32 contrib;
@@ -2587,8 +2587,11 @@ static __always_inline int __update_load_avg(u64 now, int cpu,
* period and accrue it.
*/
delta_w = 1024 - delta_w;
- if (weight)
+ if (weight) {
sa->load_sum += weight * delta_w;
+ if (cfs_rq)
+ cfs_rq->runnable_load_sum += weight * delta_w;
+ }
if (running)
sa->util_sum += delta_w * scale_freq >> SCHED_CAPACITY_SHIFT;

@@ -2599,19 +2602,28 @@ static __always_inline int __update_load_avg(u64 now, int cpu,
delta %= 1024;

sa->load_sum = decay_load(sa->load_sum, periods + 1);
+ if (cfs_rq)
+ cfs_rq->runnable_load_sum =
+ decay_load(cfs_rq->runnable_load_sum, periods + 1);
sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);

/* Efficiently calculate \sum (1..n_period) 1024*y^i */
contrib = __compute_runnable_contrib(periods);
- if (weight)
+ if (weight) {
sa->load_sum += weight * contrib;
+ if (cfs_rq)
+ cfs_rq->runnable_load_sum += weight * contrib;
+ }
if (running)
sa->util_sum += contrib * scale_freq >> SCHED_CAPACITY_SHIFT;
}

/* Remainder of delta accrued against u_0` */
- if (weight)
+ if (weight) {
sa->load_sum += weight * delta;
+ if (cfs_rq)
+ cfs_rq->runnable_load_sum += weight * delta;
+ }
if (running)
sa->util_sum += delta * scale_freq >> SCHED_CAPACITY_SHIFT;

@@ -2619,6 +2631,9 @@ static __always_inline int __update_load_avg(u64 now, int cpu,

if (decayed) {
sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
+ if (cfs_rq)
+ cfs_rq->runnable_load_avg =
+ div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
sa->util_avg = (sa->util_sum << SCHED_LOAD_SHIFT) / LOAD_AVG_MAX;
}

@@ -2666,7 +2681,7 @@ static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
}

decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
- scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL);
+ scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);

#ifndef CONFIG_64BIT
smp_wmb();
@@ -2688,7 +2703,7 @@ static inline void update_load_avg(struct sched_entity *se, int update_tg)
* track group sched_entity load average for task_h_load calc in migration
*/
__update_load_avg(now, cpu, &se->avg,
- se->on_rq * scale_load_down(se->load.weight), cfs_rq->curr == se);
+ se->on_rq * scale_load_down(se->load.weight), cfs_rq->curr == se, NULL);

if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
update_tg_load_avg(cfs_rq, 0);
@@ -2708,11 +2723,15 @@ enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
}
else {
__update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
- se->on_rq * scale_load_down(se->load.weight), cfs_rq->curr == se);
+ se->on_rq * scale_load_down(se->load.weight),
+ cfs_rq->curr == se, NULL);
}

decayed = update_cfs_rq_load_avg(now, cfs_rq);

+ cfs_rq->runnable_load_avg += sa->load_avg;
+ cfs_rq->runnable_load_sum += sa->load_sum;
+
if (migrated) {
cfs_rq->avg.load_avg += sa->load_avg;
cfs_rq->avg.load_sum += sa->load_sum;
@@ -2724,6 +2743,18 @@ enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
update_tg_load_avg(cfs_rq, 0);
}

+/* Remove the runnable load generated by se from cfs_rq's runnable load average */
+static inline void
+dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ update_load_avg(se, 1);
+
+ cfs_rq->runnable_load_avg =
+ max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
+ cfs_rq->runnable_load_sum =
+ max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
+}
+
/*
* Task first catches up with cfs_rq, and then subtract
* itself from the cfs_rq (task must be off the queue now).
@@ -2745,7 +2776,7 @@ void remove_entity_load_avg(struct sched_entity *se)
last_update_time = cfs_rq->avg.last_update_time;
#endif

- __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0);
+ __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
}
@@ -2775,6 +2806,8 @@ static int idle_balance(struct rq *this_rq);
static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
+static inline void
+dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
static inline void remove_entity_load_avg(struct sched_entity *se) {}

static inline int idle_balance(struct rq *rq)
@@ -2982,7 +3015,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
* Update run-time statistics of the 'current'.
*/
update_curr(cfs_rq);
- update_load_avg(se, 1);
+ dequeue_entity_load_avg(cfs_rq, se);

update_stats_dequeue(cfs_rq, se);
if (flags & DEQUEUE_SLEEP) {
@@ -7899,7 +7932,7 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p)
#ifdef CONFIG_SMP
/* Catch up with the cfs_rq and remove our load when we leave */
__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq), &se->avg,
- se->on_rq * scale_load_down(se->load.weight), cfs_rq->curr == se);
+ se->on_rq * scale_load_down(se->load.weight), cfs_rq->curr == se, NULL);

cfs_rq->avg.load_avg =
max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index f2b17ea..118f5ae 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -368,6 +368,8 @@ struct cfs_rq {
* CFS load tracking
*/
struct sched_avg avg;
+ u64 runnable_load_sum;
+ unsigned long runnable_load_avg;
#ifdef CONFIG_FAIR_GROUP_SCHED
unsigned long tg_load_avg_contrib;
#endif
--
2.1.4


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