Messages in this thread Patch in this message | | | From | Chengming Zhou <> | Subject | [PATCH] sched/fair: combine detach into dequeue when migrating task | Date | Wed, 8 Jun 2022 12:26:05 +0800 |
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When we are migrating task out of the CPU, we can combine detach into dequeue_entity() to save the independent detach_entity_cfs_rq() in migrate_task_rq_fair().
This optimization is like combining DO_ATTACH in the enqueue_entity() when migrating task to the CPU.
So we don't have to traverse the CFS tree twice to do these load detach and propagation.
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> --- kernel/sched/fair.c | 33 ++++++++++++++++++++++----------- 1 file changed, 22 insertions(+), 11 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e0cd4052e32f..1db7c97a5fe6 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3896,6 +3896,7 @@ static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s #define UPDATE_TG 0x1 #define SKIP_AGE_LOAD 0x2 #define DO_ATTACH 0x4 +#define DO_DETACH 0x8 /* Update task and its cfs_rq load average */ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) @@ -3913,7 +3914,14 @@ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s decayed = update_cfs_rq_load_avg(now, cfs_rq); decayed |= propagate_entity_load_avg(se); - if (!se->avg.last_update_time && (flags & DO_ATTACH)) { + if (flags & DO_DETACH) { + /* + * DO_DETACH means we're here from dequeue_entity() + * and we are migrating task out of the CPU. + */ + detach_entity_load_avg(cfs_rq, se); + update_tg_load_avg(cfs_rq); + } else if (!se->avg.last_update_time && (flags & DO_ATTACH)) { /* * DO_ATTACH means we're here from enqueue_entity(). @@ -4426,6 +4434,14 @@ static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq); static void dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { + int action = UPDATE_TG; + + /* + * If we are migrating task from the CPU, detach load_avg when dequeue. + */ + if (entity_is_task(se) && task_of(se)->on_rq == TASK_ON_RQ_MIGRATING) + action |= DO_DETACH; + /* * Update run-time statistics of the 'current'. */ @@ -4440,7 +4456,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) * - For group entity, update its weight to reflect the new share * of its group cfs_rq. */ - update_load_avg(cfs_rq, se, UPDATE_TG); + update_load_avg(cfs_rq, se, action); se_update_runnable(se); update_stats_dequeue_fair(cfs_rq, se, flags); @@ -6940,15 +6956,10 @@ static void migrate_task_rq_fair(struct task_struct *p, int new_cpu) se->vruntime -= min_vruntime; } - if (p->on_rq == TASK_ON_RQ_MIGRATING) { - /* - * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old' - * rq->lock and can modify state directly. - */ - lockdep_assert_rq_held(task_rq(p)); - detach_entity_cfs_rq(&p->se); - - } else { + /* + * In case of TASK_ON_RQ_MIGRATING we already detach in dequeue_entity. + */ + if (p->on_rq != TASK_ON_RQ_MIGRATING) { /* * We are supposed to update the task to "current" time, then * its up to date and ready to go to new CPU/cfs_rq. But we -- 2.36.1
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