Messages in this thread Patch in this message | | | Date | Mon, 26 Aug 2019 09:51:47 -0700 | From | mark gross <> | Subject | Re: [RFC PATCH v3 07/16] sched: Allow put_prev_task() to drop rq->lock |
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On Wed, May 29, 2019 at 08:36:43PM +0000, Vineeth Remanan Pillai wrote: > From: Peter Zijlstra <peterz@infradead.org> > > Currently the pick_next_task() loop is convoluted and ugly because of > how it can drop the rq->lock and needs to restart the picking. > > For the RT/Deadline classes, it is put_prev_task() where we do > balancing, and we could do this before the picking loop. Make this > possible.
Maybe explain why adding strtu rq_flags pointers to the function call supports the above commit coment.
--mark
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > kernel/sched/core.c | 2 +- > kernel/sched/deadline.c | 14 +++++++++++++- > kernel/sched/fair.c | 2 +- > kernel/sched/idle.c | 2 +- > kernel/sched/rt.c | 14 +++++++++++++- > kernel/sched/sched.h | 4 ++-- > kernel/sched/stop_task.c | 2 +- > 7 files changed, 32 insertions(+), 8 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 32ea79fb8d29..9dfa0c53deb3 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -5595,7 +5595,7 @@ static void calc_load_migrate(struct rq *rq) > atomic_long_add(delta, &calc_load_tasks); > } > > -static void put_prev_task_fake(struct rq *rq, struct task_struct *prev) > +static void put_prev_task_fake(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) > { > } > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index c02b3229e2c3..45425f971eec 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -1772,13 +1772,25 @@ pick_next_task_dl(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) > return p; > } > > -static void put_prev_task_dl(struct rq *rq, struct task_struct *p) > +static void put_prev_task_dl(struct rq *rq, struct task_struct *p, struct rq_flags *rf) > { > update_curr_dl(rq); > > update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1); > if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1) > enqueue_pushable_dl_task(rq, p); > + > + if (rf && !on_dl_rq(&p->dl) && need_pull_dl_task(rq, p)) { > + /* > + * This is OK, because current is on_cpu, which avoids it being > + * picked for load-balance and preemption/IRQs are still > + * disabled avoiding further scheduler activity on it and we've > + * not yet started the picking loop. > + */ > + rq_unpin_lock(rq, rf); > + pull_dl_task(rq); > + rq_repin_lock(rq, rf); > + } > } > > /* > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 49707b4797de..8e3eb243fd9f 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -7110,7 +7110,7 @@ done: __maybe_unused; > /* > * Account for a descheduled task: > */ > -static void put_prev_task_fair(struct rq *rq, struct task_struct *prev) > +static void put_prev_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) > { > struct sched_entity *se = &prev->se; > struct cfs_rq *cfs_rq; > diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c > index dd64be34881d..1b65a4c3683e 100644 > --- a/kernel/sched/idle.c > +++ b/kernel/sched/idle.c > @@ -373,7 +373,7 @@ static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int fl > resched_curr(rq); > } > > -static void put_prev_task_idle(struct rq *rq, struct task_struct *prev) > +static void put_prev_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) > { > } > > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > index adec98a94f2b..51ee87c5a28a 100644 > --- a/kernel/sched/rt.c > +++ b/kernel/sched/rt.c > @@ -1593,7 +1593,7 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) > return p; > } > > -static void put_prev_task_rt(struct rq *rq, struct task_struct *p) > +static void put_prev_task_rt(struct rq *rq, struct task_struct *p, struct rq_flags *rf) > { > update_curr_rt(rq); > > @@ -1605,6 +1605,18 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p) > */ > if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1) > enqueue_pushable_task(rq, p); > + > + if (rf && !on_rt_rq(&p->rt) && need_pull_rt_task(rq, p)) { > + /* > + * This is OK, because current is on_cpu, which avoids it being > + * picked for load-balance and preemption/IRQs are still > + * disabled avoiding further scheduler activity on it and we've > + * not yet started the picking loop. > + */ > + rq_unpin_lock(rq, rf); > + pull_rt_task(rq); > + rq_repin_lock(rq, rf); > + } > } > > #ifdef CONFIG_SMP > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index bfcbcbb25646..4cbe2bef92e4 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -1675,7 +1675,7 @@ struct sched_class { > struct task_struct * (*pick_next_task)(struct rq *rq, > struct task_struct *prev, > struct rq_flags *rf); > - void (*put_prev_task)(struct rq *rq, struct task_struct *p); > + void (*put_prev_task)(struct rq *rq, struct task_struct *p, struct rq_flags *rf); > void (*set_next_task)(struct rq *rq, struct task_struct *p); > > #ifdef CONFIG_SMP > @@ -1721,7 +1721,7 @@ struct sched_class { > static inline void put_prev_task(struct rq *rq, struct task_struct *prev) > { > WARN_ON_ONCE(rq->curr != prev); > - prev->sched_class->put_prev_task(rq, prev); > + prev->sched_class->put_prev_task(rq, prev, NULL); > } > > static inline void set_next_task(struct rq *rq, struct task_struct *next) > diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c > index 47a3d2a18a9a..8f414018d5e0 100644 > --- a/kernel/sched/stop_task.c > +++ b/kernel/sched/stop_task.c > @@ -59,7 +59,7 @@ static void yield_task_stop(struct rq *rq) > BUG(); /* the stop task should never yield, its pointless. */ > } > > -static void put_prev_task_stop(struct rq *rq, struct task_struct *prev) > +static void put_prev_task_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) > { > struct task_struct *curr = rq->curr; > u64 delta_exec; > -- > 2.17.1 >
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