lkml.org 
[lkml]   [2020]   [Nov]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH -tip 02/32] sched: Introduce sched_class::pick_task()
On Wed, Nov 25, 2020 at 05:28:36PM +0100, Vincent Guittot wrote:
> On Wed, 18 Nov 2020 at 00:20, Joel Fernandes (Google)

> > +#ifdef CONFIG_SMP
> > +static struct task_struct *pick_task_fair(struct rq *rq)
> > +{
> > + struct cfs_rq *cfs_rq = &rq->cfs;
> > + struct sched_entity *se;
> > +
> > + if (!cfs_rq->nr_running)
> > + return NULL;
> > +
> > + do {
> > + struct sched_entity *curr = cfs_rq->curr;
> > +
> > + se = pick_next_entity(cfs_rq, NULL);
>
> Calling pick_next_entity clears buddies. This is fine without
> coresched because the se will be the next one. But calling
> pick_task_fair doesn't mean that the se will be used

Urgh, nice one :/

> > +
> > + if (curr) {
> > + if (se && curr->on_rq)
> > + update_curr(cfs_rq);
> > +
>
> Shouldn't you check if cfs_rq is throttled ?

Hmm,... I suppose we do.

> > + if (!se || entity_before(curr, se))
> > + se = curr;
> > + }
> > +
> > + cfs_rq = group_cfs_rq(se);
> > + } while (cfs_rq);
> > +
> > + return task_of(se);
> > +}
> > +#endif

Something like so then?

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4354,6 +4354,8 @@ check_preempt_tick(struct cfs_rq *cfs_rq
static void
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
+ clear_buddies(cfs_rq, se);
+
/* 'current' is not kept within the tree. */
if (se->on_rq) {
/*
@@ -4440,8 +4442,6 @@ pick_next_entity(struct cfs_rq *cfs_rq,
se = cfs_rq->last;
}

- clear_buddies(cfs_rq, se);
-
return se;
}

@@ -6982,20 +6982,29 @@ static void check_preempt_wakeup(struct
#ifdef CONFIG_SMP
static struct task_struct *pick_task_fair(struct rq *rq)
{
- struct cfs_rq *cfs_rq = &rq->cfs;
struct sched_entity *se;
-
+ struct cfs_rq *cfs_rq;
+
+again:
+ cfs_rq = &rq->cfs;
if (!cfs_rq->nr_running)
return NULL;

do {
struct sched_entity *curr = cfs_rq->curr;

- if (curr && curr->on_rq)
- update_curr(cfs_rq);
+ /* When we pick for a remote RQ, we'll not have done put_prev_entity() */
+ if (curr) {
+ if (curr->on_rq)
+ update_curr(cfs_rq);
+ else
+ curr = NULL;

- se = pick_next_entity(cfs_rq, curr);
+ if (unlikely(check_cfs_rq_runtime(cfs_rq)))
+ goto again;
+ }

+ se = pick_next_entity(cfs_rq, curr);
cfs_rq = group_cfs_rq(se);
} while (cfs_rq);

\
 
 \ /
  Last update: 2020-11-26 10:11    [W:0.141 / U:0.204 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site