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Subject[PATCH 15/16] sched: implement usage tracking
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With the frame-work for runnable tracking now fully in place.  Per-entity usage
tracking is a simple and low-overhead addition.

Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Ben Segall <bsegall@google.com>
---
include/linux/sched.h | 1 +
kernel/sched/debug.c | 3 +++
kernel/sched/fair.c | 33 ++++++++++++++++++++++++++++-----
kernel/sched/sched.h | 4 ++--
4 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index fdfdfab..a65c097 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1142,6 +1142,7 @@ struct sched_avg {
u64 last_runnable_update;
s64 decay_count;
unsigned long load_avg_contrib;
+ u32 usage_avg_sum;
};

#ifdef CONFIG_SCHEDSTATS
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index fbd1517..e8f8d51 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -94,6 +94,7 @@ static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group
#ifdef CONFIG_SMP
P(se->avg.runnable_avg_sum);
P(se->avg.runnable_avg_period);
+ P(se->avg.usage_avg_sum);
P(se->avg.load_avg_contrib);
P(se->avg.decay_count);
#endif
@@ -233,6 +234,8 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
cfs_rq->tg_runnable_contrib);
SEQ_printf(m, " .%-30s: %d\n", "tg->runnable_avg",
atomic_read(&cfs_rq->tg->runnable_avg));
+ SEQ_printf(m, " .%-30s: %d\n", "tg->usage_avg",
+ atomic_read(&cfs_rq->tg->usage_avg));
#endif

print_cfs_group_stats(m, cpu, cfs_rq->tg);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 89c353c..3d1aaa8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -996,7 +996,8 @@ static u32 __compute_runnable_contrib(int n)
*/
static __always_inline int __update_entity_runnable_avg(u64 now,
struct sched_avg *sa,
- int runnable)
+ int runnable,
+ int running)
{
u64 delta, periods;
u32 runnable_contrib;
@@ -1035,6 +1036,8 @@ static __always_inline int __update_entity_runnable_avg(u64 now,
delta_w = 1024 - delta_w;
if (runnable)
sa->runnable_avg_sum += delta_w;
+ if (running)
+ sa->usage_avg_sum += delta_w;
sa->runnable_avg_period += delta_w;

delta -= delta_w;
@@ -1047,17 +1050,22 @@ static __always_inline int __update_entity_runnable_avg(u64 now,
periods + 1);
sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
periods + 1);
+ sa->usage_avg_sum = decay_load(sa->usage_avg_sum, periods + 1);

/* Efficiently calculate \sum (1..n_period) 1024*y^i */
runnable_contrib = __compute_runnable_contrib(periods);
if (runnable)
sa->runnable_avg_sum += runnable_contrib;
+ if (running)
+ sa->usage_avg_sum += runnable_contrib;
sa->runnable_avg_period += runnable_contrib;
}

/* Remainder of delta accrued against u_0` */
if (runnable)
sa->runnable_avg_sum += delta;
+ if (running)
+ sa->usage_avg_sum += delta;
sa->runnable_avg_period += delta;

return decayed;
@@ -1103,15 +1111,27 @@ static inline void __update_tg_runnable_avg(struct sched_avg *sa,
struct cfs_rq *cfs_rq)
{
struct task_group *tg = cfs_rq->tg;
- long contrib;
+ long contrib, usage_contrib;

contrib = div_u64(sa->runnable_avg_sum << 12,
sa->runnable_avg_period + 1);
contrib -= cfs_rq->tg_runnable_contrib;

- if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) {
+ usage_contrib = div_u64(sa->usage_avg_sum << 12,
+ sa->runnable_avg_period + 1);
+ usage_contrib -= cfs_rq->tg_usage_contrib;
+
+ /*
+ * contrib/usage at this point represent deltas, only update if they
+ * are substantive.
+ */
+ if ((abs(contrib) > cfs_rq->tg_runnable_contrib / 64) ||
+ (abs(usage_contrib) > cfs_rq->tg_usage_contrib / 64)) {
atomic_add(contrib, &tg->runnable_avg);
cfs_rq->tg_runnable_contrib += contrib;
+
+ atomic_add(usage_contrib, &tg->usage_avg);
+ cfs_rq->tg_usage_contrib += usage_contrib;
}
}

@@ -1201,7 +1221,8 @@ static inline void update_entity_load_avg(struct sched_entity *se,
else
now = cfs_rq_clock_task(group_cfs_rq(se));

- if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
+ if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq,
+ cfs_rq->curr == se))
return;

contrib_delta = __update_entity_load_avg_contrib(se);
@@ -1246,7 +1267,8 @@ static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)

static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
{
- __update_entity_runnable_avg(rq->clock_task, &rq->avg, runnable);
+ __update_entity_runnable_avg(rq->clock_task, &rq->avg, runnable,
+ runnable);
__update_tg_runnable_avg(&rq->avg, &rq->cfs);
}

@@ -1615,6 +1637,7 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
*/
update_stats_wait_end(cfs_rq, se);
__dequeue_entity(cfs_rq, se);
+ update_entity_load_avg(se, 1);
}

update_stats_curr_start(cfs_rq, se);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 67cc5e1..bb76895 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -113,7 +113,7 @@ struct task_group {

atomic_t load_weight;
atomic64_t load_avg;
- atomic_t runnable_avg;
+ atomic_t runnable_avg, usage_avg;
#endif

#ifdef CONFIG_RT_GROUP_SCHED
@@ -236,7 +236,7 @@ struct cfs_rq {
u64 last_decay;

#ifdef CONFIG_FAIR_GROUP_SCHED
- u32 tg_runnable_contrib;
+ u32 tg_runnable_contrib, tg_usage_contrib;
u64 tg_load_contrib;
#endif /* CONFIG_FAIR_GROUP_SCHED */




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