Messages in this thread | | | Date | Fri, 3 Nov 2023 14:45:21 +0800 | Subject | Re: [PATCH v2 1/1] sched/fair: Track current se's EEVDF parameters | From | Abel Wu <> |
| |
On 11/2/23 10:20 PM, Yiwei Lin Wrote: > After dequeuing the current-picked scheduling entity with > `__dequeue_entity`, its contribution to the EEVDF parameters > cfs_rq->avg_vruntime and cfs_rq->avg_load are also removed. > Because these should in fact be considered for the EEVDF algorithm, > we took curr as the special case and inserted back the contributions > when requests for cfs_rq->avg_vruntime and cfs_rq->avg_load. > > Functions like `entity_eligible` which is called insied a loop may > therefore recalculate these statistics repeatly and require more effort. > Instead, we could just avoid to remove these statistics from > cfs_rq->avg_vruntime and cfs_rq->avg_load directly. > > Signed-off-by: Yiwei Lin <s921975628@gmail.com> > --- > kernel/sched/fair.c | 39 +++++++++++---------------------------- > 1 file changed, 11 insertions(+), 28 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 876798824..a10a73603 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -655,17 +655,9 @@ void avg_vruntime_update(struct cfs_rq *cfs_rq, s64 delta) > */ > u64 avg_vruntime(struct cfs_rq *cfs_rq) > { > - struct sched_entity *curr = cfs_rq->curr; > s64 avg = cfs_rq->avg_vruntime; > long load = cfs_rq->avg_load; > > - if (curr && curr->on_rq) { > - unsigned long weight = scale_load_down(curr->load.weight); > - > - avg += entity_key(cfs_rq, curr) * weight; > - load += weight; > - } > - > if (load) { > /* sign flips effective floor / ceil */ > if (avg < 0) > @@ -722,17 +714,9 @@ static void update_entity_lag(struct cfs_rq *cfs_rq, struct sched_entity *se) > */ > int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se) > { > - struct sched_entity *curr = cfs_rq->curr; > s64 avg = cfs_rq->avg_vruntime; > long load = cfs_rq->avg_load; > > - if (curr && curr->on_rq) { > - unsigned long weight = scale_load_down(curr->load.weight); > - > - avg += entity_key(cfs_rq, curr) * weight; > - load += weight; > - } > - > return avg >= entity_key(cfs_rq, se) * load; > } > > @@ -821,11 +805,12 @@ static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) > __entity_less, &min_deadline_cb); > } > > -static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) > +static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, bool on_rq)
Please don't add such complexity. Since avg_vruntime includes the whole cfs_rq after this change, you can simply avg_vruntime_add() when doing enqueue_entity() and avg_vruntime_sub() in dequeue_entity().
> { > rb_erase_augmented_cached(&se->run_node, &cfs_rq->tasks_timeline, > &min_deadline_cb); > - avg_vruntime_sub(cfs_rq, se); > + if (!on_rq) > + avg_vruntime_sub(cfs_rq, se); > } > > struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq) > @@ -1137,6 +1122,7 @@ static void update_curr(struct cfs_rq *cfs_rq) > struct sched_entity *curr = cfs_rq->curr; > u64 now = rq_clock_task(rq_of(cfs_rq)); > u64 delta_exec; > + u64 delta_fair; > > if (unlikely(!curr)) > return; > @@ -1158,7 +1144,9 @@ static void update_curr(struct cfs_rq *cfs_rq) > curr->sum_exec_runtime += delta_exec; > schedstat_add(cfs_rq->exec_clock, delta_exec); > > - curr->vruntime += calc_delta_fair(delta_exec, curr); > + delta_fair = calc_delta_fair(delta_exec, curr); > + curr->vruntime += delta_fair; > + cfs_rq->avg_vruntime += delta_fair * scale_load_down(curr->load.weight);
What if curr->load.weight changes in this time slice?
> update_deadline(cfs_rq, curr); > update_min_vruntime(cfs_rq); > > @@ -3675,8 +3663,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, > /* commit outstanding execution time */ > if (cfs_rq->curr == se) > update_curr(cfs_rq); > - else > - avg_vruntime_sub(cfs_rq, se); > + avg_vruntime_sub(cfs_rq, se); > update_load_sub(&cfs_rq->load, se->load.weight); > } > dequeue_load_avg(cfs_rq, se); > @@ -3712,8 +3699,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, > enqueue_load_avg(cfs_rq, se); > if (se->on_rq) { > update_load_add(&cfs_rq->load, se->load.weight); > - if (cfs_rq->curr != se) > - avg_vruntime_add(cfs_rq, se); > + avg_vruntime_add(cfs_rq, se); > } > } > > @@ -5023,7 +5009,6 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) > * EEVDF: placement strategy #1 / #2 > */ > if (sched_feat(PLACE_LAG) && cfs_rq->nr_running) { > - struct sched_entity *curr = cfs_rq->curr; > unsigned long load; > > lag = se->vlag; > @@ -5081,8 +5066,6 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) > * vl_i = (W + w_i)*vl'_i / W > */ > load = cfs_rq->avg_load; > - if (curr && curr->on_rq) > - load += scale_load_down(curr->load.weight); > > lag *= load + scale_load_down(se->load.weight); > if (WARN_ON_ONCE(!load)) > @@ -5229,7 +5212,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) > > update_entity_lag(cfs_rq, se); > if (se != cfs_rq->curr) > - __dequeue_entity(cfs_rq, se); > + __dequeue_entity(cfs_rq, se, 0); > se->on_rq = 0; > account_entity_dequeue(cfs_rq, se); > > @@ -5264,7 +5247,7 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) > * runqueue. > */ > update_stats_wait_end_fair(cfs_rq, se); > - __dequeue_entity(cfs_rq, se); > + __dequeue_entity(cfs_rq, se, 1); > update_load_avg(cfs_rq, se, UPDATE_TG); > /* > * HACK, stash a copy of deadline at the point of pick in vlag,
| |