Messages in this thread Patch in this message | | | Date | Wed, 16 Aug 2023 15:40:59 +0200 | From | Peter Zijlstra <> | Subject | Re: [tip:sched/eevdf] [sched/fair] e0c2ff903c: phoronix-test-suite.blogbench.Write.final_score -34.8% regression |
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On Wed, Aug 16, 2023 at 02:37:16PM +0200, Peter Zijlstra wrote: > On Mon, Aug 14, 2023 at 08:32:55PM +0200, Mike Galbraith wrote: > > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -875,6 +875,12 @@ static struct sched_entity *pick_eevdf(s > > if (curr && (!curr->on_rq || !entity_eligible(cfs_rq, curr))) > > curr = NULL; > > > > + /* > > + * Once selected, run the task to parity to avoid overscheduling. > > + */ > > + if (sched_feat(RUN_TO_PARITY) && curr) > > + return curr; > > + > > while (node) { > > struct sched_entity *se = __node_2_se(node); > > > > So I read it wrong last night... but I rather like this idea. But > there's something missing. When curr starts a new slice it should > probably do a full repick and not stick with it. > > Let me poke at this a bit.. nice
Something like so.. it shouldn't matter much now, but might make a difference once we start mixing different slice lengths.
--- kernel/sched/fair.c | 12 ++++++++++++ kernel/sched/features.h | 1 + 2 files changed, 13 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index fe5be91c71c7..128a78f3f264 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -873,6 +873,13 @@ static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq) if (curr && (!curr->on_rq || !entity_eligible(cfs_rq, curr))) curr = NULL; + /* + * Once selected, run a task until it either becomes non-eligible or + * until it gets a new slice. See the HACK in set_next_entity(). + */ + if (sched_feat(RUN_TO_PARITY) && curr && curr->vlag == curr->deadline) + return curr; + while (node) { struct sched_entity *se = __node_2_se(node); @@ -5168,6 +5175,11 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) update_stats_wait_end_fair(cfs_rq, se); __dequeue_entity(cfs_rq, se); update_load_avg(cfs_rq, se, UPDATE_TG); + /* + * HACK, stash a copy of deadline at the point of pick in vlag, + * which isn't used until dequeue. + */ + se->vlag = se->deadline; } update_stats_curr_start(cfs_rq, se); diff --git a/kernel/sched/features.h b/kernel/sched/features.h index 61bcbf5e46a4..f770168230ae 100644 --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -6,6 +6,7 @@ */ SCHED_FEAT(PLACE_LAG, true) SCHED_FEAT(PLACE_DEADLINE_INITIAL, true) +SCHED_FEAT(RUN_TO_PARITY, true) /* * Prefer to schedule the task we woke last (assuming it failed
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