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Subject[PATCH 11/16] sched: replace update_shares weight distribution with per-entity computation
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Now that the machinery in place is in place to compute contributed load in a
bottom up fashion; replace the shares distribution code within update_shares()
accordingly.

Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Ben Segall <bsegall@google.com>
---
kernel/sched/debug.c | 8 ---
kernel/sched/fair.c | 152 +++++++-------------------------------------------
kernel/sched/sched.h | 36 ++++--------
3 files changed, 32 insertions(+), 164 deletions(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 9334c68..fbd1517 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -221,14 +221,6 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
SEQ_printf(m, " .%-30s: %ld\n", "load", cfs_rq->load.weight);
#ifdef CONFIG_FAIR_GROUP_SCHED
#ifdef CONFIG_SMP
- SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "load_avg",
- SPLIT_NS(cfs_rq->load_avg));
- SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "load_period",
- SPLIT_NS(cfs_rq->load_period));
- SEQ_printf(m, " .%-30s: %ld\n", "load_contrib",
- cfs_rq->load_contribution);
- SEQ_printf(m, " .%-30s: %d\n", "load_tg",
- atomic_read(&cfs_rq->tg->load_weight));
SEQ_printf(m, " .%-30s: %lld\n", "runnable_load_avg",
cfs_rq->runnable_load_avg);
SEQ_printf(m, " .%-30s: %lld\n", "blocked_load_avg",
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b78d03e..4a9a828 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -654,9 +654,6 @@ static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
return calc_delta_fair(sched_slice(cfs_rq, se), se);
}

-static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update);
-static void update_cfs_shares(struct cfs_rq *cfs_rq);
-
/*
* Update the current task's runtime statistics. Skip current tasks that
* are not in our scheduling class.
@@ -676,10 +673,6 @@ __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,

curr->vruntime += delta_exec_weighted;
update_min_vruntime(cfs_rq);
-
-#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
- cfs_rq->load_unacc_exec_time += delta_exec;
-#endif
}

static void update_curr(struct cfs_rq *cfs_rq)
@@ -806,72 +799,7 @@ account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
}

#ifdef CONFIG_FAIR_GROUP_SCHED
-/* we need this in update_cfs_load and load-balance functions below */
-static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
# ifdef CONFIG_SMP
-static void update_cfs_rq_load_contribution(struct cfs_rq *cfs_rq,
- int global_update)
-{
- struct task_group *tg = cfs_rq->tg;
- long load_avg;
-
- load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1);
- load_avg -= cfs_rq->load_contribution;
-
- if (global_update || abs(load_avg) > cfs_rq->load_contribution / 8) {
- atomic_add(load_avg, &tg->load_weight);
- cfs_rq->load_contribution += load_avg;
- }
-}
-
-static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
-{
- u64 period = sysctl_sched_shares_window;
- u64 now, delta;
- unsigned long load = cfs_rq->load.weight;
-
- if (cfs_rq->tg == &root_task_group || throttled_hierarchy(cfs_rq))
- return;
-
- now = rq_of(cfs_rq)->clock_task;
- 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;
- delta = period - 1;
- }
-
- cfs_rq->load_stamp = now;
- cfs_rq->load_unacc_exec_time = 0;
- cfs_rq->load_period += delta;
- if (load) {
- cfs_rq->load_last = now;
- cfs_rq->load_avg += delta * load;
- }
-
- /* consider updating load contribution on each fold or truncate */
- if (global_update || cfs_rq->load_period > period
- || !cfs_rq->load_period)
- update_cfs_rq_load_contribution(cfs_rq, global_update);
-
- while (cfs_rq->load_period > period) {
- /*
- * Inline assembly required to prevent the compiler
- * optimising this loop into a divmod call.
- * See __iter_div_u64_rem() for another example of this.
- */
- asm("" : "+rm" (cfs_rq->load_period));
- cfs_rq->load_period /= 2;
- cfs_rq->load_avg /= 2;
- }
-
- if (!cfs_rq->curr && !cfs_rq->nr_running && !cfs_rq->load_avg)
- list_del_leaf_cfs_rq(cfs_rq);
-}
-
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
long tg_weight;
@@ -881,8 +809,8 @@ static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
* to gain a more accurate current total weight. See
* update_cfs_rq_load_contribution().
*/
- tg_weight = atomic_read(&tg->load_weight);
- tg_weight -= cfs_rq->load_contribution;
+ tg_weight = atomic64_read(&tg->load_avg);
+ tg_weight -= cfs_rq->tg_load_contrib;
tg_weight += cfs_rq->load.weight;

return tg_weight;
@@ -906,27 +834,11 @@ static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)

return shares;
}
-
-static void update_entity_shares_tick(struct cfs_rq *cfs_rq)
-{
- if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) {
- update_cfs_load(cfs_rq, 0);
- update_cfs_shares(cfs_rq);
- }
-}
# else /* CONFIG_SMP */
-static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
-{
-}
-
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
{
return tg->shares;
}
-
-static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
-{
-}
# endif /* CONFIG_SMP */
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
unsigned long weight)
@@ -944,6 +856,8 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
account_entity_enqueue(cfs_rq, se);
}

+static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
+
static void update_cfs_shares(struct cfs_rq *cfs_rq)
{
struct task_group *tg;
@@ -963,17 +877,9 @@ static void update_cfs_shares(struct cfs_rq *cfs_rq)
reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
-static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
-{
-}
-
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
{
}
-
-static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
-{
-}
#endif /* CONFIG_FAIR_GROUP_SCHED */

#ifdef CONFIG_SMP
@@ -1473,7 +1379,6 @@ 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);
enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
account_entity_enqueue(cfs_rq, se);
update_cfs_shares(cfs_rq);
@@ -1570,7 +1475,6 @@ 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);
account_entity_dequeue(cfs_rq, se);

/*
@@ -1739,11 +1643,6 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
update_entity_load_avg(curr, 1);
update_cfs_rq_blocked_load(cfs_rq, 1);

- /*
- * Update share accounting for long-running entities.
- */
- update_entity_shares_tick(cfs_rq);
-
#ifdef CONFIG_SCHED_HRTICK
/*
* queued ticks are scheduled to match the slice, so don't bother
@@ -1988,18 +1887,9 @@ static int tg_unthrottle_up(struct task_group *tg, void *data)
cfs_rq->throttle_count--;
#ifdef CONFIG_SMP
if (!cfs_rq->throttle_count) {
- u64 delta = rq->clock_task - cfs_rq->load_stamp;
-
- /* leaving throttled state, advance shares averaging windows */
- cfs_rq->load_stamp += delta;
- cfs_rq->load_last += delta;
-
/* adjust cfs_rq_clock_task() */
cfs_rq->throttled_clock_task_time += rq->clock_task -
cfs_rq->throttled_clock_task;
-
- /* update entity weight now that we are on_rq again */
- update_cfs_shares(cfs_rq);
}
#endif

@@ -2011,11 +1901,9 @@ static int tg_throttle_down(struct task_group *tg, void *data)
struct rq *rq = data;
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

- /* group is entering throttled state, record last load */
- if (!cfs_rq->throttle_count) {
- update_cfs_load(cfs_rq, 0);
+ /* group is entering throttled state, stop time */
+ if (!cfs_rq->throttle_count)
cfs_rq->throttled_clock_task = rq->clock_task;
- }
cfs_rq->throttle_count++;

return 0;
@@ -2613,7 +2501,6 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
if (cfs_rq_throttled(cfs_rq))
break;

- update_cfs_load(cfs_rq, 0);
update_cfs_shares(cfs_rq);
update_entity_load_avg(se, 1);
}
@@ -2675,7 +2562,6 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
if (cfs_rq_throttled(cfs_rq))
break;

- update_cfs_load(cfs_rq, 0);
update_cfs_shares(cfs_rq);
update_entity_load_avg(se, 1);
}
@@ -3794,27 +3680,33 @@ out:
*/
static int update_shares_cpu(struct task_group *tg, int cpu)
{
+ struct sched_entity *se;
struct cfs_rq *cfs_rq;
unsigned long flags;
struct rq *rq;

- if (!tg->se[cpu])
- return 0;

rq = cpu_rq(cpu);
+ se = tg->se[cpu];
cfs_rq = tg->cfs_rq[cpu];

raw_spin_lock_irqsave(&rq->lock, flags);

update_rq_clock(rq);
- update_cfs_load(cfs_rq, 1);
update_cfs_rq_blocked_load(cfs_rq, 1);
+ update_entity_load_avg(tg->se[cpu], 1);

- /*
- * We need to update shares after updating tg->load_weight in
- * order to adjust the weight of groups with long running tasks.
- */
- update_cfs_shares(cfs_rq);
+ if (se) {
+ /*
+ * We can pivot on the runnable average decaying to zero for
+ * list removal since the parent average will always be >=
+ * child.
+ */
+ if (se->avg.runnable_avg_sum)
+ update_cfs_shares(cfs_rq);
+ else
+ list_del_leaf_cfs_rq(cfs_rq);
+ }

raw_spin_unlock_irqrestore(&rq->lock, flags);

@@ -5830,10 +5722,6 @@ void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,

cfs_rq->tg = tg;
cfs_rq->rq = rq;
-#ifdef CONFIG_SMP
- /* allow initial update_cfs_load() to truncate */
- cfs_rq->load_stamp = 1;
-#endif
init_cfs_rq_runtime(cfs_rq);

tg->cfs_rq[cpu] = cfs_rq;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 60c0935..67cc5e1 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -234,11 +234,21 @@ struct cfs_rq {
u64 runnable_load_avg, blocked_load_avg;
atomic64_t decay_counter, removed_load;
u64 last_decay;
+
#ifdef CONFIG_FAIR_GROUP_SCHED
u32 tg_runnable_contrib;
u64 tg_load_contrib;
-#endif
-#endif
+#endif /* CONFIG_FAIR_GROUP_SCHED */
+
+ /*
+ * h_load = weight * f(tg)
+ *
+ * Where f(tg) is the recursive weight fraction assigned to
+ * this group.
+ */
+ unsigned long h_load;
+#endif /* CONFIG_SMP */
+
#ifdef CONFIG_FAIR_GROUP_SCHED
struct rq *rq; /* cpu runqueue to which this cfs_rq is attached */

@@ -254,28 +264,6 @@ struct cfs_rq {
struct list_head leaf_cfs_rq_list;
struct task_group *tg; /* group that "owns" this runqueue */

-#ifdef CONFIG_SMP
- /*
- * h_load = weight * f(tg)
- *
- * Where f(tg) is the recursive weight fraction assigned to
- * this group.
- */
- unsigned long h_load;
-
- /*
- * Maintaining per-cpu shares distribution for group scheduling
- *
- * load_stamp is the last time we updated the load average
- * load_last is the last time we updated the load average and saw load
- * load_unacc_exec_time is currently unaccounted execution time
- */
- u64 load_avg;
- u64 load_period;
- u64 load_stamp, load_last, load_unacc_exec_time;
-
- unsigned long load_contribution;
-#endif /* CONFIG_SMP */
#ifdef CONFIG_CFS_BANDWIDTH
int runtime_enabled;
u64 runtime_expires;



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