Messages in this thread |  | | From | Vincent Guittot <> | Date | Wed, 25 Nov 2020 17:28:36 +0100 | Subject | Re: [PATCH -tip 02/32] sched: Introduce sched_class::pick_task() |
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On Wed, 18 Nov 2020 at 00:20, Joel Fernandes (Google) <joel@joelfernandes.org> wrote: > > From: Peter Zijlstra <peterz@infradead.org> > > Because sched_class::pick_next_task() also implies > sched_class::set_next_task() (and possibly put_prev_task() and > newidle_balance) it is not state invariant. This makes it unsuitable > for remote task selection. > > Tested-by: Julien Desfossez <jdesfossez@digitalocean.com> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Signed-off-by: Vineeth Remanan Pillai <viremana@linux.microsoft.com> > Signed-off-by: Julien Desfossez <jdesfossez@digitalocean.com> > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> > --- > kernel/sched/deadline.c | 16 ++++++++++++++-- > kernel/sched/fair.c | 32 +++++++++++++++++++++++++++++++- > kernel/sched/idle.c | 8 ++++++++ > kernel/sched/rt.c | 15 +++++++++++++-- > kernel/sched/sched.h | 3 +++ > kernel/sched/stop_task.c | 14 ++++++++++++-- > 6 files changed, 81 insertions(+), 7 deletions(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index 0f2ea0a3664c..abfc8b505d0d 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -1867,7 +1867,7 @@ static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq, > return rb_entry(left, struct sched_dl_entity, rb_node); > } > > -static struct task_struct *pick_next_task_dl(struct rq *rq) > +static struct task_struct *pick_task_dl(struct rq *rq) > { > struct sched_dl_entity *dl_se; > struct dl_rq *dl_rq = &rq->dl; > @@ -1879,7 +1879,18 @@ static struct task_struct *pick_next_task_dl(struct rq *rq) > dl_se = pick_next_dl_entity(rq, dl_rq); > BUG_ON(!dl_se); > p = dl_task_of(dl_se); > - set_next_task_dl(rq, p, true); > + > + return p; > +} > + > +static struct task_struct *pick_next_task_dl(struct rq *rq) > +{ > + struct task_struct *p; > + > + p = pick_task_dl(rq); > + if (p) > + set_next_task_dl(rq, p, true); > + > return p; > } > > @@ -2551,6 +2562,7 @@ DEFINE_SCHED_CLASS(dl) = { > > #ifdef CONFIG_SMP > .balance = balance_dl, > + .pick_task = pick_task_dl, > .select_task_rq = select_task_rq_dl, > .migrate_task_rq = migrate_task_rq_dl, > .set_cpus_allowed = set_cpus_allowed_dl, > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 52ddfec7cea6..12cf068eeec8 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -4459,7 +4459,7 @@ pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) > * Avoid running the skip buddy, if running something else can > * be done without getting too unfair. > */ > - if (cfs_rq->skip == se) { > + if (cfs_rq->skip && cfs_rq->skip == se) { > struct sched_entity *second; > > if (se == curr) { > @@ -7017,6 +7017,35 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ > set_last_buddy(se); > } > > +#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
> + > + if (curr) { > + if (se && curr->on_rq) > + update_curr(cfs_rq); > +
Shouldn't you check if cfs_rq is throttled ?
> + if (!se || entity_before(curr, se)) > + se = curr; > + } > + > + cfs_rq = group_cfs_rq(se); > + } while (cfs_rq); > + > + return task_of(se); > +} > +#endif > + > struct task_struct * > pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) > { > @@ -11219,6 +11248,7 @@ DEFINE_SCHED_CLASS(fair) = { > > #ifdef CONFIG_SMP > .balance = balance_fair, > + .pick_task = pick_task_fair, > .select_task_rq = select_task_rq_fair, > .migrate_task_rq = migrate_task_rq_fair, > > diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c > index 50e128b899c4..33864193a2f9 100644 > --- a/kernel/sched/idle.c > +++ b/kernel/sched/idle.c > @@ -406,6 +406,13 @@ static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool fir > schedstat_inc(rq->sched_goidle); > } > > +#ifdef CONFIG_SMP > +static struct task_struct *pick_task_idle(struct rq *rq) > +{ > + return rq->idle; > +} > +#endif > + > struct task_struct *pick_next_task_idle(struct rq *rq) > { > struct task_struct *next = rq->idle; > @@ -473,6 +480,7 @@ DEFINE_SCHED_CLASS(idle) = { > > #ifdef CONFIG_SMP > .balance = balance_idle, > + .pick_task = pick_task_idle, > .select_task_rq = select_task_rq_idle, > .set_cpus_allowed = set_cpus_allowed_common, > #endif > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > index a6f9d132c24f..a0e245b0c4bd 100644 > --- a/kernel/sched/rt.c > +++ b/kernel/sched/rt.c > @@ -1626,7 +1626,7 @@ static struct task_struct *_pick_next_task_rt(struct rq *rq) > return rt_task_of(rt_se); > } > > -static struct task_struct *pick_next_task_rt(struct rq *rq) > +static struct task_struct *pick_task_rt(struct rq *rq) > { > struct task_struct *p; > > @@ -1634,7 +1634,17 @@ static struct task_struct *pick_next_task_rt(struct rq *rq) > return NULL; > > p = _pick_next_task_rt(rq); > - set_next_task_rt(rq, p, true); > + > + return p; > +} > + > +static struct task_struct *pick_next_task_rt(struct rq *rq) > +{ > + struct task_struct *p = pick_task_rt(rq); > + > + if (p) > + set_next_task_rt(rq, p, true); > + > return p; > } > > @@ -2483,6 +2493,7 @@ DEFINE_SCHED_CLASS(rt) = { > > #ifdef CONFIG_SMP > .balance = balance_rt, > + .pick_task = pick_task_rt, > .select_task_rq = select_task_rq_rt, > .set_cpus_allowed = set_cpus_allowed_common, > .rq_online = rq_online_rt, > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index f794c9337047..5a0dd2b312aa 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -1839,6 +1839,9 @@ struct sched_class { > #ifdef CONFIG_SMP > int (*balance)(struct rq *rq, struct task_struct *prev, struct rq_flags *rf); > int (*select_task_rq)(struct task_struct *p, int task_cpu, int flags); > + > + struct task_struct * (*pick_task)(struct rq *rq); > + > void (*migrate_task_rq)(struct task_struct *p, int new_cpu); > > void (*task_woken)(struct rq *this_rq, struct task_struct *task); > diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c > index 55f39125c0e1..f988ebe3febb 100644 > --- a/kernel/sched/stop_task.c > +++ b/kernel/sched/stop_task.c > @@ -34,15 +34,24 @@ static void set_next_task_stop(struct rq *rq, struct task_struct *stop, bool fir > stop->se.exec_start = rq_clock_task(rq); > } > > -static struct task_struct *pick_next_task_stop(struct rq *rq) > +static struct task_struct *pick_task_stop(struct rq *rq) > { > if (!sched_stop_runnable(rq)) > return NULL; > > - set_next_task_stop(rq, rq->stop, true); > return rq->stop; > } > > +static struct task_struct *pick_next_task_stop(struct rq *rq) > +{ > + struct task_struct *p = pick_task_stop(rq); > + > + if (p) > + set_next_task_stop(rq, p, true); > + > + return p; > +} > + > static void > enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags) > { > @@ -123,6 +132,7 @@ DEFINE_SCHED_CLASS(stop) = { > > #ifdef CONFIG_SMP > .balance = balance_stop, > + .pick_task = pick_task_stop, > .select_task_rq = select_task_rq_stop, > .set_cpus_allowed = set_cpus_allowed_common, > #endif > -- > 2.29.2.299.gdc1121823c-goog >
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