Messages in this thread | | | Date | Thu, 30 Apr 2015 13:05:46 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH 1/2] sched/rt: Check to push task away when its affinity is changed |
| |
On Fri, 1 May 2015 00:33:17 +0800 Xunlei Pang <xlpang@126.com> wrote:
> From: Xunlei Pang <pang.xunlei@linaro.org> > > We may suffer from extra rt overload rq due to the affinity, > so when the affinity of any runnable rt task is changed, we > should check to trigger balancing, otherwise it will cause > some unnecessary delayed real-time response. Unfortunately, > current RT global scheduler does nothing about this. > > For example: a 2-cpu system with two runnable FIFO tasks(same > rt_priority) bound on CPU0, let's name them rt1(running) and > rt2(runnable) respectively; CPU1 has no RTs. Then, someone sets > the affinity of rt2 to 0x3(i.e. CPU0 and CPU1), but after this, > rt2 still can't be scheduled enters schedule(), this > definitely causes some/big response latency for rt2. > > This patch introduces a new sched_class::post_set_cpus_allowed() > for RT called after set_cpus_allowed_rt(). In this new function, > if the task is runnable but not running, it tries to push it away > once it got migratable. > > Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org> > --- > kernel/sched/core.c | 3 +++ > kernel/sched/rt.c | 17 +++++++++++++++++ > kernel/sched/sched.h | 1 + > 3 files changed, 21 insertions(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index d13fc13..64a1603 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -4773,6 +4773,9 @@ void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) > > cpumask_copy(&p->cpus_allowed, new_mask); > p->nr_cpus_allowed = cpumask_weight(new_mask); > + > + if (p->sched_class->post_set_cpus_allowed) > + p->sched_class->post_set_cpus_allowed(p); > } > > /* > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > index cc49a7c..a9d33a3 100644 > --- a/kernel/sched/rt.c > +++ b/kernel/sched/rt.c > @@ -2281,6 +2281,22 @@ static void set_cpus_allowed_rt(struct task_struct *p, > update_rt_migration(&rq->rt); > } > > +static void post_set_cpus_allowed_rt(struct task_struct *p) > +{ > + struct rq *rq; > + > + if (!task_on_rq_queued(p)) > + return; > + > + rq = task_rq(p); > + if (!task_running(rq, p) && > + p->nr_cpus_allowed > 1 && > + !test_tsk_need_resched(rq->curr) && > + cpupri_find(&rq->rd->cpupri, p, NULL)) {
I don't think we need cpupri_find() call here. It's done in push_rt_tasks() and doing it twice is just a wasted effort.
> + push_rt_tasks(rq); > + } > +} > + > /* Assumes rq->lock is held */ > static void rq_online_rt(struct rq *rq) > { > @@ -2495,6 +2511,7 @@ const struct sched_class rt_sched_class = { > .select_task_rq = select_task_rq_rt, > > .set_cpus_allowed = set_cpus_allowed_rt, > + .post_set_cpus_allowed = post_set_cpus_allowed_rt, > .rq_online = rq_online_rt, > .rq_offline = rq_offline_rt, > .post_schedule = post_schedule_rt, > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index e0e1299..6f90645 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -1191,6 +1191,7 @@ struct sched_class { > > void (*set_cpus_allowed)(struct task_struct *p, > const struct cpumask *newmask); > + void (*post_set_cpus_allowed)(struct task_struct *p); > > void (*rq_online)(struct rq *rq); > void (*rq_offline)(struct rq *rq);
| |