[tip: sched/core] sched/eevdf: More PELT vs DELAYED_DEQUEUE

tip-bot2 for Peter Zijlstra
2024-09-10T08:09:30Z

The following commit has been merged into the sched/core branch of tip:

Commit-ID: 2e05f6c71d36f8ae1410a1cf3f12848cc17916e9
Gitweb: https://git.kernel.org/tip/2e05f6c71d36f8ae1410a1cf3f12848cc17916e9
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 06 Sep 2024 12:45:25 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 10 Sep 2024 09:51:15 +02:00

sched/eevdf: More PELT vs DELAYED_DEQUEUE

Vincent and Dietmar noted that while commit fc1892becd56 fixes the
entity runnable stats, it does not adjust the cfs_rq runnable stats,
which are based off of h_nr_running.

Track h_nr_delayed such that we can discount those and adjust the
signal.

Fixes: fc1892becd56 ("sched/eevdf: Fixup PELT vs DELAYED_DEQUEUE")
Reported-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reported-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20240906104525.GG4928@noisy.programming.kicks-ass.net
---
kernel/sched/debug.c | 1 +-
kernel/sched/fair.c | 49 ++++++++++++++++++++++++++++++++++++++-----
kernel/sched/pelt.c | 2 +-
kernel/sched/sched.h | 7 ++++--
4 files changed, 51 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index de1dc52..35974ac 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -844,6 +844,7 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "spread", SPLIT_NS(spread));
SEQ_printf(m, " .%-30s: %d\n", "nr_running", cfs_rq->nr_running);
SEQ_printf(m, " .%-30s: %d\n", "h_nr_running", cfs_rq->h_nr_running);
+ SEQ_printf(m, " .%-30s: %d\n", "h_nr_delayed", cfs_rq->h_nr_delayed);
SEQ_printf(m, " .%-30s: %d\n", "idle_nr_running",
cfs_rq->idle_nr_running);
SEQ_printf(m, " .%-30s: %d\n", "idle_h_nr_running",
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 922d690..0bc5e62 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5456,9 +5456,31 @@ static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)

static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);

-static inline void finish_delayed_dequeue_entity(struct sched_entity *se)
+static void set_delayed(struct sched_entity *se)
+{
+ se->sched_delayed = 1;
+ for_each_sched_entity(se) {
+ struct cfs_rq *cfs_rq = cfs_rq_of(se);
+ cfs_rq->h_nr_delayed++;
+ if (cfs_rq_throttled(cfs_rq))
+ break;
+ }
+}
+
+static void clear_delayed(struct sched_entity *se)
{
se->sched_delayed = 0;
+ for_each_sched_entity(se) {
+ struct cfs_rq *cfs_rq = cfs_rq_of(se);
+ cfs_rq->h_nr_delayed--;
+ if (cfs_rq_throttled(cfs_rq))
+ break;
+ }
+}
+
+static inline void finish_delayed_dequeue_entity(struct sched_entity *se)
+{
+ clear_delayed(se);
if (sched_feat(DELAY_ZERO) && se->vlag > 0)
se->vlag = 0;
}
@@ -5488,7 +5510,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
if (cfs_rq->next == se)
cfs_rq->next = NULL;
update_load_avg(cfs_rq, se, 0);
- se->sched_delayed = 1;
+ set_delayed(se);
return false;
}
}
@@ -5907,7 +5929,7 @@ static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
struct rq *rq = rq_of(cfs_rq);
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
struct sched_entity *se;
- long task_delta, idle_task_delta, dequeue = 1;
+ long task_delta, idle_task_delta, delayed_delta, dequeue = 1;
long rq_h_nr_running = rq->cfs.h_nr_running;

raw_spin_lock(&cfs_b->lock);
@@ -5940,6 +5962,7 @@ static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)

task_delta = cfs_rq->h_nr_running;
idle_task_delta = cfs_rq->idle_h_nr_running;
+ delayed_delta = cfs_rq->h_nr_delayed;
for_each_sched_entity(se) {
struct cfs_rq *qcfs_rq = cfs_rq_of(se);
int flags;
@@ -5963,6 +5986,7 @@ static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)

qcfs_rq->h_nr_running -= task_delta;
qcfs_rq->idle_h_nr_running -= idle_task_delta;
+ qcfs_rq->h_nr_delayed -= delayed_delta;

if (qcfs_rq->load.weight) {
/* Avoid re-evaluating load for this entity: */
@@ -5985,6 +6009,7 @@ static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)

qcfs_rq->h_nr_running -= task_delta;
qcfs_rq->idle_h_nr_running -= idle_task_delta;
+ qcfs_rq->h_nr_delayed -= delayed_delta;
}

/* At this point se is NULL and we are at root level*/
@@ -6010,7 +6035,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
struct rq *rq = rq_of(cfs_rq);
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
struct sched_entity *se;
- long task_delta, idle_task_delta;
+ long task_delta, idle_task_delta, delayed_delta;
long rq_h_nr_running = rq->cfs.h_nr_running;

se = cfs_rq->tg->se[cpu_of(rq)];
@@ -6046,6 +6071,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)

task_delta = cfs_rq->h_nr_running;
idle_task_delta = cfs_rq->idle_h_nr_running;
+ delayed_delta = cfs_rq->h_nr_delayed;
for_each_sched_entity(se) {
struct cfs_rq *qcfs_rq = cfs_rq_of(se);

@@ -6060,6 +6086,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)

qcfs_rq->h_nr_running += task_delta;
qcfs_rq->idle_h_nr_running += idle_task_delta;
+ qcfs_rq->h_nr_delayed += delayed_delta;

/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(qcfs_rq))
@@ -6077,6 +6104,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)

qcfs_rq->h_nr_running += task_delta;
qcfs_rq->idle_h_nr_running += idle_task_delta;
+ qcfs_rq->h_nr_delayed += delayed_delta;

/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(qcfs_rq))
@@ -6930,7 +6958,7 @@ requeue_delayed_entity(struct sched_entity *se)
}

update_load_avg(cfs_rq, se, 0);
- se->sched_delayed = 0;
+ clear_delayed(se);
}

/*
@@ -6944,6 +6972,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
struct cfs_rq *cfs_rq;
struct sched_entity *se = &p->se;
int idle_h_nr_running = task_has_idle_policy(p);
+ int h_nr_delayed = 0;
int task_new = !(flags & ENQUEUE_WAKEUP);
int rq_h_nr_running = rq->cfs.h_nr_running;
u64 slice = 0;
@@ -6970,6 +6999,9 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
if (p->in_iowait)
cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);

+ if (task_new)
+ h_nr_delayed = !!se->sched_delayed;
+
for_each_sched_entity(se) {
if (se->on_rq) {
if (se->sched_delayed)
@@ -6992,6 +7024,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)

cfs_rq->h_nr_running++;
cfs_rq->idle_h_nr_running += idle_h_nr_running;
+ cfs_rq->h_nr_delayed += h_nr_delayed;

if (cfs_rq_is_idle(cfs_rq))
idle_h_nr_running = 1;
@@ -7015,6 +7048,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)

cfs_rq->h_nr_running++;
cfs_rq->idle_h_nr_running += idle_h_nr_running;
+ cfs_rq->h_nr_delayed += h_nr_delayed;

if (cfs_rq_is_idle(cfs_rq))
idle_h_nr_running = 1;
@@ -7077,6 +7111,7 @@ static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags)
struct task_struct *p = NULL;
int idle_h_nr_running = 0;
int h_nr_running = 0;
+ int h_nr_delayed = 0;
struct cfs_rq *cfs_rq;
u64 slice = 0;

@@ -7084,6 +7119,8 @@ static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags)
p = task_of(se);
h_nr_running = 1;
idle_h_nr_running = task_has_idle_policy(p);
+ if (!task_sleep && !task_delayed)
+ h_nr_delayed = !!se->sched_delayed;
} else {
cfs_rq = group_cfs_rq(se);
slice = cfs_rq_min_slice(cfs_rq);
@@ -7101,6 +7138,7 @@ static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags)

cfs_rq->h_nr_running -= h_nr_running;
cfs_rq->idle_h_nr_running -= idle_h_nr_running;
+ cfs_rq->h_nr_delayed -= h_nr_delayed;

if (cfs_rq_is_idle(cfs_rq))
idle_h_nr_running = h_nr_running;
@@ -7139,6 +7177,7 @@ static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags)

cfs_rq->h_nr_running -= h_nr_running;
cfs_rq->idle_h_nr_running -= idle_h_nr_running;
+ cfs_rq->h_nr_delayed -= h_nr_delayed;

if (cfs_rq_is_idle(cfs_rq))
idle_h_nr_running = h_nr_running;
diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c
index fa52906..21e3ff5 100644
--- a/kernel/sched/pelt.c
+++ b/kernel/sched/pelt.c
@@ -321,7 +321,7 @@ int __update_load_avg_cfs_rq(u64 now, struct cfs_rq *cfs_rq)
{
if (___update_load_sum(now, &cfs_rq->avg,
scale_load_down(cfs_rq->load.weight),
- cfs_rq->h_nr_running,
+ cfs_rq->h_nr_running - cfs_rq->h_nr_delayed,
cfs_rq->curr != NULL)) {

___update_load_avg(&cfs_rq->avg, 1);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 3744f16..d91360b 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -603,6 +603,7 @@ struct cfs_rq {
unsigned int h_nr_running; /* SCHED_{NORMAL,BATCH,IDLE} */
unsigned int idle_nr_running; /* SCHED_IDLE */
unsigned int idle_h_nr_running; /* SCHED_IDLE */
+ unsigned int h_nr_delayed;

s64 avg_vruntime;
u64 avg_load;
@@ -813,8 +814,10 @@ struct dl_rq {

static inline void se_update_runnable(struct sched_entity *se)
{
- if (!entity_is_task(se))
- se->runnable_weight = se->my_q->h_nr_running;
+ if (!entity_is_task(se)) {
+ struct cfs_rq *cfs_rq = se->my_q;
+ se->runnable_weight = cfs_rq->h_nr_running - cfs_rq->h_nr_delayed;
+ }
}

static inline long se_runnable(struct sched_entity *se)