[PATCH v2 25/35] sched/fair: refactor update_curr(), entity_tick()

Ankur Arora
2024-05-28T00:37:01Z

When updating the task's runtime statistics via update_curr()
or entity_tick(), we call resched_curr() to resched if needed.

Refactor update_curr() and entity_tick() to only update the stats
and deferring any rescheduling needed to task_tick_fair() or
update_curr().

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Suggested-by: Peter Ziljstra <peterz@infradead.org>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
kernel/sched/fair.c | 54 ++++++++++++++++++++++-----------------------
1 file changed, 27 insertions(+), 27 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c5171c247466..dd34709f294c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -981,10 +981,10 @@ static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se);
* XXX: strictly: vd_i += N*r_i/w_i such that: vd_i > ve_i
* this is probably good enough.
*/
-static void update_deadline(struct cfs_rq *cfs_rq, struct sched_entity *se)
+static bool update_deadline(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
if ((s64)(se->vruntime - se->deadline) < 0)
- return;
+ return false;

/*
* For EEVDF the virtual time slope is determined by w_i (iow.
@@ -1002,9 +1002,11 @@ static void update_deadline(struct cfs_rq *cfs_rq, struct sched_entity *se)
* The task has consumed its request, reschedule.
*/
if (cfs_rq->nr_running > 1) {
- resched_curr(rq_of(cfs_rq));
clear_buddies(cfs_rq, se);
+ return true;
}
+
+ return false;
}

#include "pelt.h"
@@ -1159,26 +1161,35 @@ s64 update_curr_common(struct rq *rq)
/*
* Update the current task's runtime statistics.
*/
-static void update_curr(struct cfs_rq *cfs_rq)
+static bool __update_curr(struct cfs_rq *cfs_rq)
{
struct sched_entity *curr = cfs_rq->curr;
s64 delta_exec;
+ bool resched;

if (unlikely(!curr))
- return;
+ return false;

delta_exec = update_curr_se(rq_of(cfs_rq), curr);
if (unlikely(delta_exec <= 0))
- return;
+ return false;

curr->vruntime += calc_delta_fair(delta_exec, curr);
- update_deadline(cfs_rq, curr);
+ resched = update_deadline(cfs_rq, curr);
update_min_vruntime(cfs_rq);

if (entity_is_task(curr))
update_curr_task(task_of(curr), delta_exec);

account_cfs_rq_runtime(cfs_rq, delta_exec);
+
+ return resched;
+}
+
+static void update_curr(struct cfs_rq *cfs_rq)
+{
+ if (__update_curr(cfs_rq))
+ resched_curr(rq_of(cfs_rq));
}

static void update_curr_fair(struct rq *rq)
@@ -5499,13 +5510,13 @@ static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
cfs_rq->curr = NULL;
}

-static void
-entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
+static bool
+entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
/*
* Update run-time statistics of the 'current'.
*/
- update_curr(cfs_rq);
+ bool resched = __update_curr(cfs_rq);

/*
* Ensure that runnable average is periodically updated.
@@ -5513,22 +5524,7 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
update_load_avg(cfs_rq, curr, UPDATE_TG);
update_cfs_group(curr);

-#ifdef CONFIG_SCHED_HRTICK
- /*
- * queued ticks are scheduled to match the slice, so don't bother
- * validating it and just reschedule.
- */
- if (queued) {
- resched_curr(rq_of(cfs_rq));
- return;
- }
- /*
- * don't let the period tick interfere with the hrtick preemption
- */
- if (!sched_feat(DOUBLE_TICK) &&
- hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
- return;
-#endif
+ return resched;
}

@@ -12611,12 +12607,16 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
{
struct cfs_rq *cfs_rq;
struct sched_entity *se = &curr->se;
+ bool resched = false;

for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
- entity_tick(cfs_rq, se, queued);
+ resched |= entity_tick(cfs_rq, se);
}

+ if (resched)
+ resched_curr(rq);
+
if (static_branch_unlikely(&sched_numa_balancing))
task_tick_numa(rq, curr);

--
2.31.1