From: Cheng Chao <cs.os.kernel@gmail.com>
To: peterz@infradead.org
Cc: mingo@kernel.org, oleg@redhat.com, tj@kernel.org,
akpm@linux-foundation.org, chris@chris-wilson.co.uk,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4] stop_machine: Avoid a sleep and wakeup in the stop_one_cpu()
Date: Sun, 18 Sep 2016 10:07:30 +0800 [thread overview]
Message-ID: <61f8640f-1530-467b-fb9e-ba8028c075ab@gmail.com> (raw)
In-Reply-To: <1473818510-6779-1-git-send-email-cs.os.kernel@gmail.com>
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;
> }
>
next prev parent reply other threads:[~2016-09-18 2:07 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <OF73BCE1E4.D2224FEC-ON48258025.0022CFA7-48258025.0022E3DC@kedacom.com>
2016-09-09 8:13 ` [PATCH v2] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Cheng Chao
2016-09-09 8:19 ` chengchao
2016-09-09 13:14 ` Oleg Nesterov
2016-09-09 16:24 ` Peter Zijlstra
2016-09-10 8:52 ` [PATCH v3] " Cheng Chao
2016-09-10 9:51 ` Cheng Chao
2016-09-10 16:33 ` Peter Zijlstra
2016-09-12 11:03 ` Oleg Nesterov
2016-09-13 2:45 ` Cheng Chao
2016-09-12 11:37 ` Peter Zijlstra
2016-09-12 11:41 ` Peter Zijlstra
2016-09-12 13:05 ` Oleg Nesterov
2016-09-12 15:01 ` Peter Zijlstra
2016-09-13 16:14 ` Oleg Nesterov
2016-09-13 16:37 ` Peter Zijlstra
2016-09-14 2:07 ` Cheng Chao
2016-09-14 7:50 ` Peter Zijlstra
2016-09-14 15:45 ` Oleg Nesterov
2016-09-22 13:59 ` [tip:sched/core] sched/core: Optimize __schedule() tip-bot for Peter Zijlstra
2016-09-13 4:03 ` [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Cheng Chao
2016-09-13 8:45 ` Peter Zijlstra
2016-09-14 2:01 ` [PATCH v4] stop_machine: Avoid a sleep and wakeup in the stop_one_cpu() Cheng Chao
2016-09-14 15:53 ` Oleg Nesterov
2016-09-18 2:07 ` Cheng Chao [this message]
2016-09-22 13:59 ` [tip:sched/core] stop_machine: Avoid a sleep and wakeup in stop_one_cpu() tip-bot for Cheng Chao
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