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- Prevent incorrect dequeueing of the deadline dlserver helper task and fix

Browse Source 
its time accounting
 
 - Properly track the CFS runqueue runnable stats
 
 - Check the total number of all queued tasks in a sched fair's runqueue
   hierarchy before deciding to stop the tick
 
 - Fix the scheduling of the task that got woken last (NEXT_BUDDY) by
   preventing those from being delayed
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Merge tag 'sched_urgent_for_v6.13_rc3-p2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Borislav Petkov:

 - Prevent incorrect dequeueing of the deadline dlserver helper task and
   fix its time accounting

 - Properly track the CFS runqueue runnable stats

 - Check the total number of all queued tasks in a sched fair's runqueue
   hierarchy before deciding to stop the tick

 - Fix the scheduling of the task that got woken last (NEXT_BUDDY) by
   preventing those from being delayed

* tag 'sched_urgent_for_v6.13_rc3-p2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/dlserver: Fix dlserver time accounting
  sched/dlserver: Fix dlserver double enqueue
  sched/eevdf: More PELT vs DELAYED_DEQUEUE
  sched/fair: Fix sched_can_stop_tick() for fair tasks
  sched/fair: Fix NEXT_BUDDY
This commit is contained in:
Linus Torvalds 2024-12-15 09:38:03 -08:00
commit acd855a949
7 changed files with 84 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/sched.h
View File

@ -656,6 +656,12 @@ struct sched_dl_entity {
* @dl_defer_armed tells if the deferrable server is waiting
* for the replenishment timer to activate it.
*
* @dl_server_active tells if the dlserver is active(started).
* dlserver is started on first cfs enqueue on an idle runqueue
* and is stopped when a dequeue results in 0 cfs tasks on the
* runqueue. In other words, dlserver is active only when cpu's
* runqueue has atleast one cfs task.
*
* @dl_defer_running tells if the deferrable server is actually
* running, skipping the defer phase.
*/
@ -664,6 +670,7 @@ struct sched_dl_entity {
unsigned int dl_non_contending : 1;
unsigned int dl_overrun : 1;
unsigned int dl_server : 1;
unsigned int dl_server_active : 1;
unsigned int dl_defer : 1;
unsigned int dl_defer_armed : 1;
unsigned int dl_defer_running : 1;

2
kernel/sched/core.c
View File

@ -1341,7 +1341,7 @@ bool sched_can_stop_tick(struct rq *rq)
if (scx_enabled() && !scx_can_stop_tick(rq))
return false;
if (rq->cfs.nr_running > 1)
if (rq->cfs.h_nr_running > 1)
return false;
/*

8
kernel/sched/deadline.c
View File

@ -1647,6 +1647,7 @@ void dl_server_start(struct sched_dl_entity *dl_se)
if (!dl_se->dl_runtime)
return;
dl_se->dl_server_active = 1;
enqueue_dl_entity(dl_se, ENQUEUE_WAKEUP);
if (!dl_task(dl_se->rq->curr) || dl_entity_preempt(dl_se, &rq->curr->dl))
resched_curr(dl_se->rq);
@ -1661,6 +1662,7 @@ void dl_server_stop(struct sched_dl_entity *dl_se)
hrtimer_try_to_cancel(&dl_se->dl_timer);
dl_se->dl_defer_armed = 0;
dl_se->dl_throttled = 0;
dl_se->dl_server_active = 0;
}
void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq,
@ -2421,8 +2423,10 @@ static struct task_struct *__pick_task_dl(struct rq *rq)
if (dl_server(dl_se)) {
p = dl_se->server_pick_task(dl_se);
if (!p) {
dl_se->dl_yielded = 1;
update_curr_dl_se(rq, dl_se, 0);
if (dl_server_active(dl_se)) {
dl_se->dl_yielded = 1;
update_curr_dl_se(rq, dl_se, 0);
}
goto again;
}
rq->dl_server = dl_se;

1
kernel/sched/debug.c
View File

@ -845,6 +845,7 @@ 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",

73
kernel/sched/fair.c
View File

@ -1159,8 +1159,6 @@ static inline void update_curr_task(struct task_struct *p, s64 delta_exec)
trace_sched_stat_runtime(p, delta_exec);
account_group_exec_runtime(p, delta_exec);
cgroup_account_cputime(p, delta_exec);
if (p->dl_server)
dl_server_update(p->dl_server, delta_exec);
}
static inline bool did_preempt_short(struct cfs_rq *cfs_rq, struct sched_entity *curr)
@ -1237,11 +1235,16 @@ static void update_curr(struct cfs_rq *cfs_rq)
update_curr_task(p, delta_exec);
/*
* Any fair task that runs outside of fair_server should
* account against fair_server such that it can account for
* this time and possibly avoid running this period.
* If the fair_server is active, we need to account for the
* fair_server time whether or not the task is running on
* behalf of fair_server or not:
* - If the task is running on behalf of fair_server, we need
* to limit its time based on the assigned runtime.
* - Fair task that runs outside of fair_server should account
* against fair_server such that it can account for this time
* and possibly avoid running this period.
*/
if (p->dl_server != &rq->fair_server)
if (dl_server_active(&rq->fair_server))
dl_server_update(&rq->fair_server, delta_exec);
}
@ -5471,9 +5474,33 @@ 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;
}
@ -5484,6 +5511,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
bool sleep = flags & DEQUEUE_SLEEP;
update_curr(cfs_rq);
clear_buddies(cfs_rq, se);
if (flags & DEQUEUE_DELAYED) {
SCHED_WARN_ON(!se->sched_delayed);
@ -5500,10 +5528,8 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
if (sched_feat(DELAY_DEQUEUE) && delay &&
!entity_eligible(cfs_rq, se)) {
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;
}
}
@ -5526,8 +5552,6 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
update_stats_dequeue_fair(cfs_rq, se, flags);
clear_buddies(cfs_rq, se);
update_entity_lag(cfs_rq, se);
if (sched_feat(PLACE_REL_DEADLINE) && !sleep) {
se->deadline -= se->vruntime;
@ -5917,7 +5941,7 @@ 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);
@ -5950,6 +5974,7 @@ 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;
@ -5973,6 +5998,7 @@ 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: */
@ -5995,6 +6021,7 @@ 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*/
@ -6020,7 +6047,7 @@ 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)];
@ -6056,6 +6083,7 @@ 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);
@ -6073,6 +6101,7 @@ 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))
@ -6090,6 +6119,7 @@ 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))
@ -6943,7 +6973,7 @@ requeue_delayed_entity(struct sched_entity *se)
}
update_load_avg(cfs_rq, se, 0);
se->sched_delayed = 0;
clear_delayed(se);
}
/*
@ -6957,6 +6987,7 @@ 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;
@ -6983,6 +7014,9 @@ 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)
@ -7005,6 +7039,7 @@ 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;
@ -7028,6 +7063,7 @@ 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;
@ -7090,6 +7126,7 @@ 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;
@ -7097,6 +7134,8 @@ 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);
@ -7114,6 +7153,7 @@ 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;
@ -7152,6 +7192,7 @@ 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;
@ -8780,7 +8821,7 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
return;
if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK)) {
if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK) && !pse->sched_delayed) {
set_next_buddy(pse);
}

2
kernel/sched/pelt.c
View File

@ -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);

13
kernel/sched/sched.h
View File

@ -398,6 +398,11 @@ extern void __dl_server_attach_root(struct sched_dl_entity *dl_se, struct rq *rq
extern int dl_server_apply_params(struct sched_dl_entity *dl_se,
u64 runtime, u64 period, bool init);
static inline bool dl_server_active(struct sched_dl_entity *dl_se)
{
return dl_se->dl_server_active;
}
#ifdef CONFIG_CGROUP_SCHED
extern struct list_head task_groups;
@ -649,6 +654,7 @@ 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;
@ -898,8 +904,11 @@ 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)