Messages in this thread | | | Subject | Re: [PATCH v4] stop_machine: Avoid a sleep and wakeup in the stop_one_cpu() | From | Cheng Chao <> | Date | Sun, 18 Sep 2016 10:07:30 +0800 |
| |
Hi Peter,
What should I do next? Thanks.
Cheng
on 09/14/2016 10:01 AM, Cheng Chao wrote: > In case @cpu == smp_proccessor_id(), we can avoid a sleep+wakeup > by doing a preemption. > > the caller such as sched_exec can benefit from this change. > > Signed-off-by: Cheng Chao <cs.os.kernel@gmail.com> > Cc: Oleg Nesterov <oleg@redhat.com> > Cc: Peter Zijlstra <peterz@infradead.org> > --- > kernel/sched/core.c | 8 ++++++-- > kernel/stop_machine.c | 5 +++++ > 2 files changed, 11 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index a0086a5..283b662 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1063,8 +1063,12 @@ static int migration_cpu_stop(void *data) > * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because > * we're holding p->pi_lock. > */ > - if (task_rq(p) == rq && task_on_rq_queued(p)) > - rq = __migrate_task(rq, p, arg->dest_cpu); > + if (task_rq(p) == rq) { > + if (task_on_rq_queued(p)) > + rq = __migrate_task(rq, p, arg->dest_cpu); > + else > + p->wake_cpu = arg->dest_cpu; > + } > raw_spin_unlock(&rq->lock); > raw_spin_unlock(&p->pi_lock); > > diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c > index 4a1ca5f..1a24890 100644 > --- a/kernel/stop_machine.c > +++ b/kernel/stop_machine.c > @@ -126,6 +126,11 @@ int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg) > cpu_stop_init_done(&done, 1); > if (!cpu_stop_queue_work(cpu, &work)) > return -ENOENT; > + /* > + * In case @cpu == smp_proccessor_id() we can avoid a sleep+wakeup > + * by doing a preemption. > + */ > + cond_resched(); > wait_for_completion(&done.completion); > return done.ret; > } >
| |