[tip:sched/core] sched/debug: Remove several CONFIG_SCHEDSTATS guards

From: tip-bot for Josh Poimboeuf
Date: Mon Sep 05 2016 - 07:58:56 EST

Commit-ID: 4fa8d299b43a91f871f6d5b00dd5ab33d43bbc2c
Gitweb: http://git.kernel.org/tip/4fa8d299b43a91f871f6d5b00dd5ab33d43bbc2c
Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate: Fri, 17 Jun 2016 12:43:26 -0500
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 5 Sep 2016 13:29:47 +0200

sched/debug: Remove several CONFIG_SCHEDSTATS guards

Clean up the sched code by removing several of the CONFIG_SCHEDSTATS
guards, using schedstat_*() macros where needed.

Code size:

!CONFIG_SCHEDSTATS defconfig:

text data bss dec hex filename
10209818 4368184 1105920 15683922 ef5152 vmlinux.before.nostats
10209818 4368184 1105920 15683922 ef5152 vmlinux.after.nostats

CONFIG_SCHEDSTATS defconfig:

text data bss dec hex filename
10214210 4370040 1105920 15690170 ef69ba vmlinux.before.stats
10214210 4370680 1105920 15690810 ef6c3a vmlinux.after.stats

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/e51e0ebe5af95ac295de720dd252e7c0d2142e4a.1466184592.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/core.c | 33 +++++-------
kernel/sched/debug.c | 99 ++++++++++++++++++----------------
kernel/sched/fair.c | 148 ++++++++++++++++++++++++---------------------------
3 files changed, 136 insertions(+), 144 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 8506770..860070f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1629,13 +1629,15 @@ static inline int __set_cpus_allowed_ptr(struct task_struct *p,
static void
ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
{
-#ifdef CONFIG_SCHEDSTATS
- struct rq *rq = this_rq();
+ struct rq *rq;

-#ifdef CONFIG_SMP
- int this_cpu = smp_processor_id();
+ if (!schedstat_enabled())
+ return;
+
+ rq = this_rq();

- if (cpu == this_cpu) {
+#ifdef CONFIG_SMP
+ if (cpu == rq->cpu) {
schedstat_inc(rq->ttwu_local);
schedstat_inc(p->se.statistics.nr_wakeups_local);
} else {
@@ -1643,7 +1645,7 @@ ttwu_stat(struct task_struct *p, int cpu, int wake_flags)

schedstat_inc(p->se.statistics.nr_wakeups_remote);
rcu_read_lock();
- for_each_domain(this_cpu, sd) {
+ for_each_domain(rq->cpu, sd) {
if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
schedstat_inc(sd->ttwu_wake_remote);
break;
@@ -1654,7 +1656,6 @@ ttwu_stat(struct task_struct *p, int cpu, int wake_flags)

if (wake_flags & WF_MIGRATED)
schedstat_inc(p->se.statistics.nr_wakeups_migrate);
-
#endif /* CONFIG_SMP */

schedstat_inc(rq->ttwu_count);
@@ -1662,8 +1663,6 @@ ttwu_stat(struct task_struct *p, int cpu, int wake_flags)

if (wake_flags & WF_SYNC)
schedstat_inc(p->se.statistics.nr_wakeups_sync);
-
-#endif /* CONFIG_SCHEDSTATS */
}

static inline void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
@@ -2084,8 +2083,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)

ttwu_queue(p, cpu, wake_flags);
stat:
- if (schedstat_enabled())
- ttwu_stat(p, cpu, wake_flags);
+ ttwu_stat(p, cpu, wake_flags);
out:
raw_spin_unlock_irqrestore(&p->pi_lock, flags);

@@ -2134,8 +2132,7 @@ static void try_to_wake_up_local(struct task_struct *p, struct pin_cookie cookie
ttwu_activate(rq, p, ENQUEUE_WAKEUP);

ttwu_do_wakeup(rq, p, 0, cookie);
- if (schedstat_enabled())
- ttwu_stat(p, smp_processor_id(), 0);
+ ttwu_stat(p, smp_processor_id(), 0);
out:
raw_spin_unlock(&p->pi_lock);
}
@@ -7675,12 +7672,10 @@ void normalize_rt_tasks(void)
if (p->flags & PF_KTHREAD)
continue;

- p->se.exec_start = 0;
-#ifdef CONFIG_SCHEDSTATS
- p->se.statistics.wait_start = 0;
- p->se.statistics.sleep_start = 0;
- p->se.statistics.block_start = 0;
-#endif
+ p->se.exec_start = 0;
+ schedstat_set(p->se.statistics.wait_start, 0);
+ schedstat_set(p->se.statistics.sleep_start, 0);
+ schedstat_set(p->se.statistics.block_start, 0);

if (!dl_task(p) && !rt_task(p)) {
/*
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 63ffcaa..1393588 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -369,8 +369,12 @@ static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group

#define P(F) \
SEQ_printf(m, " .%-30s: %lld\n", #F, (long long)F)
+#define P_SCHEDSTAT(F) \
+ SEQ_printf(m, " .%-30s: %lld\n", #F, (long long)schedstat_val(F))
#define PN(F) \
SEQ_printf(m, " .%-30s: %lld.%06ld\n", #F, SPLIT_NS((long long)F))
+#define PN_SCHEDSTAT(F) \
+ SEQ_printf(m, " .%-30s: %lld.%06ld\n", #F, SPLIT_NS((long long)schedstat_val(F)))

if (!se)
return;
@@ -378,26 +382,27 @@ static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group
PN(se->exec_start);
PN(se->vruntime);
PN(se->sum_exec_runtime);
-#ifdef CONFIG_SCHEDSTATS
if (schedstat_enabled()) {
- PN(se->statistics.wait_start);
- PN(se->statistics.sleep_start);
- PN(se->statistics.block_start);
- PN(se->statistics.sleep_max);
- PN(se->statistics.block_max);
- PN(se->statistics.exec_max);
- PN(se->statistics.slice_max);
- PN(se->statistics.wait_max);
- PN(se->statistics.wait_sum);
- P(se->statistics.wait_count);
+ PN_SCHEDSTAT(se->statistics.wait_start);
+ PN_SCHEDSTAT(se->statistics.sleep_start);
+ PN_SCHEDSTAT(se->statistics.block_start);
+ PN_SCHEDSTAT(se->statistics.sleep_max);
+ PN_SCHEDSTAT(se->statistics.block_max);
+ PN_SCHEDSTAT(se->statistics.exec_max);
+ PN_SCHEDSTAT(se->statistics.slice_max);
+ PN_SCHEDSTAT(se->statistics.wait_max);
+ PN_SCHEDSTAT(se->statistics.wait_sum);
+ P_SCHEDSTAT(se->statistics.wait_count);
}
-#endif
P(se->load.weight);
#ifdef CONFIG_SMP
P(se->avg.load_avg);
P(se->avg.util_avg);
#endif
+
+#undef PN_SCHEDSTAT
#undef PN
+#undef P_SCHEDSTAT
#undef P
}
#endif
@@ -626,9 +631,7 @@ do { \
#undef P64
#endif

-#ifdef CONFIG_SCHEDSTATS
-#define P(n) SEQ_printf(m, " .%-30s: %d\n", #n, rq->n);
-
+#define P(n) SEQ_printf(m, " .%-30s: %d\n", #n, schedstat_val(rq->n));
if (schedstat_enabled()) {
P(yld_count);
P(sched_count);
@@ -636,9 +639,8 @@ do { \
P(ttwu_count);
P(ttwu_local);
}
-
#undef P
-#endif
+
spin_lock_irqsave(&sched_debug_lock, flags);
print_cfs_stats(m, cpu);
print_rt_stats(m, cpu);
@@ -868,10 +870,14 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
SEQ_printf(m, "%-45s:%21Ld\n", #F, (long long)F)
#define P(F) \
SEQ_printf(m, "%-45s:%21Ld\n", #F, (long long)p->F)
+#define P_SCHEDSTAT(F) \
+ SEQ_printf(m, "%-45s:%21Ld\n", #F, (long long)schedstat_val(p->F))
#define __PN(F) \
SEQ_printf(m, "%-45s:%14Ld.%06ld\n", #F, SPLIT_NS((long long)F))
#define PN(F) \
SEQ_printf(m, "%-45s:%14Ld.%06ld\n", #F, SPLIT_NS((long long)p->F))
+#define PN_SCHEDSTAT(F) \
+ SEQ_printf(m, "%-45s:%14Ld.%06ld\n", #F, SPLIT_NS((long long)schedstat_val(p->F)))

PN(se.exec_start);
PN(se.vruntime);
@@ -881,37 +887,36 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)

P(se.nr_migrations);

-#ifdef CONFIG_SCHEDSTATS
if (schedstat_enabled()) {
u64 avg_atom, avg_per_cpu;

- PN(se.statistics.sum_sleep_runtime);
- PN(se.statistics.wait_start);
- PN(se.statistics.sleep_start);
- PN(se.statistics.block_start);
- PN(se.statistics.sleep_max);
- PN(se.statistics.block_max);
- PN(se.statistics.exec_max);
- PN(se.statistics.slice_max);
- PN(se.statistics.wait_max);
- PN(se.statistics.wait_sum);
- P(se.statistics.wait_count);
- PN(se.statistics.iowait_sum);
- P(se.statistics.iowait_count);
- P(se.statistics.nr_migrations_cold);
- P(se.statistics.nr_failed_migrations_affine);
- P(se.statistics.nr_failed_migrations_running);
- P(se.statistics.nr_failed_migrations_hot);
- P(se.statistics.nr_forced_migrations);
- P(se.statistics.nr_wakeups);
- P(se.statistics.nr_wakeups_sync);
- P(se.statistics.nr_wakeups_migrate);
- P(se.statistics.nr_wakeups_local);
- P(se.statistics.nr_wakeups_remote);
- P(se.statistics.nr_wakeups_affine);
- P(se.statistics.nr_wakeups_affine_attempts);
- P(se.statistics.nr_wakeups_passive);
- P(se.statistics.nr_wakeups_idle);
+ PN_SCHEDSTAT(se.statistics.sum_sleep_runtime);
+ PN_SCHEDSTAT(se.statistics.wait_start);
+ PN_SCHEDSTAT(se.statistics.sleep_start);
+ PN_SCHEDSTAT(se.statistics.block_start);
+ PN_SCHEDSTAT(se.statistics.sleep_max);
+ PN_SCHEDSTAT(se.statistics.block_max);
+ PN_SCHEDSTAT(se.statistics.exec_max);
+ PN_SCHEDSTAT(se.statistics.slice_max);
+ PN_SCHEDSTAT(se.statistics.wait_max);
+ PN_SCHEDSTAT(se.statistics.wait_sum);
+ P_SCHEDSTAT(se.statistics.wait_count);
+ PN_SCHEDSTAT(se.statistics.iowait_sum);
+ P_SCHEDSTAT(se.statistics.iowait_count);
+ P_SCHEDSTAT(se.statistics.nr_migrations_cold);
+ P_SCHEDSTAT(se.statistics.nr_failed_migrations_affine);
+ P_SCHEDSTAT(se.statistics.nr_failed_migrations_running);
+ P_SCHEDSTAT(se.statistics.nr_failed_migrations_hot);
+ P_SCHEDSTAT(se.statistics.nr_forced_migrations);
+ P_SCHEDSTAT(se.statistics.nr_wakeups);
+ P_SCHEDSTAT(se.statistics.nr_wakeups_sync);
+ P_SCHEDSTAT(se.statistics.nr_wakeups_migrate);
+ P_SCHEDSTAT(se.statistics.nr_wakeups_local);
+ P_SCHEDSTAT(se.statistics.nr_wakeups_remote);
+ P_SCHEDSTAT(se.statistics.nr_wakeups_affine);
+ P_SCHEDSTAT(se.statistics.nr_wakeups_affine_attempts);
+ P_SCHEDSTAT(se.statistics.nr_wakeups_passive);
+ P_SCHEDSTAT(se.statistics.nr_wakeups_idle);

avg_atom = p->se.sum_exec_runtime;
if (nr_switches)
@@ -930,7 +935,7 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
__PN(avg_atom);
__PN(avg_per_cpu);
}
-#endif
+
__P(nr_switches);
SEQ_printf(m, "%-45s:%21Ld\n",
"nr_voluntary_switches", (long long)p->nvcsw);
@@ -947,8 +952,10 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
#endif
P(policy);
P(prio);
+#undef PN_SCHEDSTAT
#undef PN
#undef __PN
+#undef P_SCHEDSTAT
#undef P
#undef __P

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 157d741..a6820b3 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -821,26 +821,34 @@ static void update_curr_fair(struct rq *rq)
update_curr(cfs_rq_of(&rq->curr->se));
}

-#ifdef CONFIG_SCHEDSTATS
static inline void
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
- u64 wait_start = rq_clock(rq_of(cfs_rq));
+ u64 wait_start, prev_wait_start;
+
+ if (!schedstat_enabled())
+ return;
+
+ wait_start = rq_clock(rq_of(cfs_rq));
+ prev_wait_start = schedstat_val(se->statistics.wait_start);

if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
- likely(wait_start > se->statistics.wait_start))
- wait_start -= se->statistics.wait_start;
+ likely(wait_start > prev_wait_start))
+ wait_start -= prev_wait_start;

- se->statistics.wait_start = wait_start;
+ schedstat_set(se->statistics.wait_start, wait_start);
}

-static void
+static inline void
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
struct task_struct *p;
u64 delta;

- delta = rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start;
+ if (!schedstat_enabled())
+ return;
+
+ delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);

if (entity_is_task(se)) {
p = task_of(se);
@@ -850,59 +858,67 @@ update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
* time stamp can be adjusted to accumulate wait time
* prior to migration.
*/
- se->statistics.wait_start = delta;
+ schedstat_set(se->statistics.wait_start, delta);
return;
}
trace_sched_stat_wait(p, delta);
}

- se->statistics.wait_max = max(se->statistics.wait_max, delta);
- se->statistics.wait_count++;
- se->statistics.wait_sum += delta;
- se->statistics.wait_start = 0;
+ schedstat_set(se->statistics.wait_max,
+ max(schedstat_val(se->statistics.wait_max), delta));
+ schedstat_inc(se->statistics.wait_count);
+ schedstat_add(se->statistics.wait_sum, delta);
+ schedstat_set(se->statistics.wait_start, 0);
}

-static void
+static inline void
update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
struct task_struct *tsk = NULL;
+ u64 sleep_start, block_start;
+
+ if (!schedstat_enabled())
+ return;
+
+ sleep_start = schedstat_val(se->statistics.sleep_start);
+ block_start = schedstat_val(se->statistics.block_start);

if (entity_is_task(se))
tsk = task_of(se);

- if (se->statistics.sleep_start) {
- u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
+ if (sleep_start) {
+ u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;

if ((s64)delta < 0)
delta = 0;

- if (unlikely(delta > se->statistics.sleep_max))
- se->statistics.sleep_max = delta;
+ if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
+ schedstat_set(se->statistics.sleep_max, delta);

- se->statistics.sleep_start = 0;
- se->statistics.sum_sleep_runtime += delta;
+ schedstat_set(se->statistics.sleep_start, 0);
+ schedstat_add(se->statistics.sum_sleep_runtime, delta);

if (tsk) {
account_scheduler_latency(tsk, delta >> 10, 1);
trace_sched_stat_sleep(tsk, delta);
}
}
- if (se->statistics.block_start) {
- u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
+ if (block_start) {
+ u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;

if ((s64)delta < 0)
delta = 0;

- if (unlikely(delta > se->statistics.block_max))
- se->statistics.block_max = delta;
+ if (unlikely(delta > schedstat_val(se->statistics.block_max)))
+ schedstat_set(se->statistics.block_max, delta);

- se->statistics.block_start = 0;
- se->statistics.sum_sleep_runtime += delta;
+ schedstat_set(se->statistics.block_start, 0);
+ schedstat_add(se->statistics.sum_sleep_runtime, delta);

if (tsk) {
if (tsk->in_iowait) {
- se->statistics.iowait_sum += delta;
- se->statistics.iowait_count++;
+ schedstat_add(se->statistics.iowait_sum, delta);
+ schedstat_inc(se->statistics.iowait_count);
trace_sched_stat_iowait(tsk, delta);
}

@@ -929,6 +945,9 @@ update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
static inline void
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
+ if (!schedstat_enabled())
+ return;
+
/*
* Are we enqueueing a waiting task? (for current tasks
* a dequeue/enqueue event is a NOP)
@@ -943,6 +962,10 @@ update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
static inline void
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
+
+ if (!schedstat_enabled())
+ return;
+
/*
* Mark the end of the wait period if dequeueing a
* waiting task:
@@ -950,45 +973,18 @@ update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
if (se != cfs_rq->curr)
update_stats_wait_end(cfs_rq, se);

- if (flags & DEQUEUE_SLEEP) {
- if (entity_is_task(se)) {
- struct task_struct *tsk = task_of(se);
+ if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
+ struct task_struct *tsk = task_of(se);

- if (tsk->state & TASK_INTERRUPTIBLE)
- se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
- if (tsk->state & TASK_UNINTERRUPTIBLE)
- se->statistics.block_start = rq_clock(rq_of(cfs_rq));
- }
+ if (tsk->state & TASK_INTERRUPTIBLE)
+ schedstat_set(se->statistics.sleep_start,
+ rq_clock(rq_of(cfs_rq)));
+ if (tsk->state & TASK_UNINTERRUPTIBLE)
+ schedstat_set(se->statistics.block_start,
+ rq_clock(rq_of(cfs_rq)));
}
-
-}
-#else
-static inline void
-update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
-{
-}
-
-static inline void
-update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
-{
-}
-
-static inline void
-update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
-{
}

-static inline void
-update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
-{
-}
-
-static inline void
-update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
-{
-}
-#endif
-
/*
* We are picking a new current task - update its stats:
*/
@@ -3396,10 +3392,8 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
place_entity(cfs_rq, se, 0);

check_schedstat_required();
- if (schedstat_enabled()) {
- update_stats_enqueue(cfs_rq, se, flags);
- check_spread(cfs_rq, se);
- }
+ update_stats_enqueue(cfs_rq, se, flags);
+ check_spread(cfs_rq, se);
if (!curr)
__enqueue_entity(cfs_rq, se);
se->on_rq = 1;
@@ -3466,8 +3460,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
update_curr(cfs_rq);
dequeue_entity_load_avg(cfs_rq, se);

- if (schedstat_enabled())
- update_stats_dequeue(cfs_rq, se, flags);
+ update_stats_dequeue(cfs_rq, se, flags);

clear_buddies(cfs_rq, se);

@@ -3541,25 +3534,25 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
* a CPU. So account for the time it spent waiting on the
* runqueue.
*/
- if (schedstat_enabled())
- update_stats_wait_end(cfs_rq, se);
+ update_stats_wait_end(cfs_rq, se);
__dequeue_entity(cfs_rq, se);
update_load_avg(se, 1);
}

update_stats_curr_start(cfs_rq, se);
cfs_rq->curr = se;
-#ifdef CONFIG_SCHEDSTATS
+
/*
* Track our maximum slice length, if the CPU's load is at
* least twice that of our own weight (i.e. dont track it
* when there are only lesser-weight tasks around):
*/
if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
- se->statistics.slice_max = max(se->statistics.slice_max,
- se->sum_exec_runtime - se->prev_sum_exec_runtime);
+ schedstat_set(se->statistics.slice_max,
+ max((u64)schedstat_val(se->statistics.slice_max),
+ se->sum_exec_runtime - se->prev_sum_exec_runtime));
}
-#endif
+
se->prev_sum_exec_runtime = se->sum_exec_runtime;
}

@@ -3638,13 +3631,10 @@ static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
/* throttle cfs_rqs exceeding runtime */
check_cfs_rq_runtime(cfs_rq);

- if (schedstat_enabled()) {
- check_spread(cfs_rq, prev);
- if (prev->on_rq)
- update_stats_wait_start(cfs_rq, prev);
- }
+ check_spread(cfs_rq, prev);

if (prev->on_rq) {
+ update_stats_wait_start(cfs_rq, prev);
/* Put 'current' back into the tree. */
__enqueue_entity(cfs_rq, prev);
/* in !on_rq case, update occurred at dequeue */