From: Vincent Guittot <vincent.guittot@linaro.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Phil Auld <pauld@redhat.com>, Ming Lei <ming.lei@redhat.com>,
linux-block <linux-block@vger.kernel.org>,
linux-fs <linux-fsdevel@vger.kernel.org>,
linux-xfs <linux-xfs@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Jeff Moyer <jmoyer@redhat.com>,
Dave Chinner <dchinner@redhat.com>,
Eric Sandeen <sandeen@redhat.com>, Christoph Hellwig <hch@lst.de>,
Jens Axboe <axboe@kernel.dk>, Ingo Molnar <mingo@redhat.com>,
Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH v4] sched/core: Preempt current task in favour of bound kthread
Date: Thu, 12 Dec 2019 12:20:01 +0100 [thread overview]
Message-ID: <CAKfTPtCUm5vuvNiWszJ5tWHxmcZ2v_KexOxnBHLUkBcqC-P3fw@mail.gmail.com> (raw)
In-Reply-To: <20191212102327.GI2871@hirez.programming.kicks-ass.net>
On Thu, 12 Dec 2019 at 11:23, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Thu, Dec 12, 2019 at 11:14:24AM +0100, Peter Zijlstra wrote:
> > On Thu, Dec 12, 2019 at 11:10:31AM +0100, Peter Zijlstra wrote:
> > > @@ -4156,13 +4159,13 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
> > > if (delta_exec < sysctl_sched_min_granularity)
> > > return;
> > >
> > > - se = __pick_first_entity(cfs_rq);
> > > + se = __pick_next_entity(cfs_rq, NULL);
> > > delta = curr->vruntime - se->vruntime;
> > >
> > > if (delta < 0)
> > > return;
> >
> > What I mean with the below comment is, when this isn't enough, try
> > something like:
> >
> > if (se == cfs_rq->next)
> > ideal_runtime /= 2;
> >
> > to make it yield sooner to 'next' buddies. Sadly, due to the whole
> > cgroup mess, we can't say what actual task is on the end of it (without
> > doing a full hierarchy pick, which is more expensive still).
>
> Just for giggles, that'd look something like:
>
> while (!entity_is_task(se) {
> cfs_rq = group_cfs_rq(se);
> se = pick_next_entity(cfs_rq, cfs_rq->curr);
> }
> p = task_of(se);
>
> if (is_per_cpu_kthread(p))
> ideal_runtime /= 2;
>
> the core-scheduling patch set includes the right primitive for this I
> think, pick_task_fair().
why not only updating wan_gran() which is the only function which uses
sysctl_sched_wakeup_granularity ?
For per cpu kthread, we could set the gran to sched_min_granularity
instead of scaling it with thread's priority so per cpu kthread can
still preempt current ask even if sysctl_sched_wakeup_granularity is
large
>
> > > - if (delta > ideal_runtime)
> > > + if (delta > ideal_runtime) // maybe frob this too ?
> > > resched_curr(rq_of(cfs_rq));
> > > }
next prev parent reply other threads:[~2019-12-12 11:20 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-14 11:31 single aio thread is migrated crazily by scheduler Ming Lei
2019-11-14 13:14 ` Peter Zijlstra
2019-11-15 0:09 ` Ming Lei
2019-11-15 14:16 ` Ming Lei
2019-11-14 23:54 ` Dave Chinner
2019-11-15 1:08 ` Ming Lei
2019-11-15 4:56 ` Dave Chinner
2019-11-15 7:08 ` Ming Lei
2019-11-15 23:40 ` Dave Chinner
2019-11-16 6:31 ` Ming Lei
2019-11-18 9:21 ` Peter Zijlstra
2019-11-18 14:54 ` Vincent Guittot
2019-11-18 20:40 ` Dave Chinner
2019-11-20 19:16 ` Peter Zijlstra
2019-11-20 22:03 ` Phil Auld
2019-11-21 4:12 ` Ming Lei
2019-11-21 14:12 ` Phil Auld
2019-11-21 15:02 ` Boaz Harrosh
2019-11-21 16:19 ` Jens Axboe
2019-12-09 16:58 ` Srikar Dronamraju
2019-11-21 22:10 ` Dave Chinner
2019-11-21 13:29 ` Peter Zijlstra
2019-11-21 14:21 ` Phil Auld
2019-12-09 16:51 ` Srikar Dronamraju
2019-12-09 23:17 ` Dave Chinner
2019-12-10 3:27 ` Srikar Dronamraju
2019-12-10 5:43 ` [PATCH v2] sched/core: Preempt current task in favour of bound kthread Srikar Dronamraju
2019-12-10 9:26 ` Peter Zijlstra
2019-12-10 9:33 ` Peter Zijlstra
2019-12-10 10:18 ` Srikar Dronamraju
2019-12-10 10:16 ` Srikar Dronamraju
2019-12-10 9:43 ` Vincent Guittot
2019-12-10 10:11 ` Srikar Dronamraju
2019-12-10 11:02 ` Vincent Guittot
2019-12-10 17:23 ` [PATCH v3] " Srikar Dronamraju
2019-12-11 17:38 ` [PATCH v4] " Srikar Dronamraju
2019-12-11 22:46 ` Dave Chinner
2019-12-12 10:10 ` Peter Zijlstra
2019-12-12 10:14 ` Peter Zijlstra
2019-12-12 10:23 ` Peter Zijlstra
2019-12-12 11:20 ` Vincent Guittot [this message]
2019-12-12 13:12 ` Peter Zijlstra
2019-12-12 15:07 ` Srikar Dronamraju
2019-12-12 15:15 ` Peter Zijlstra
2019-12-13 5:32 ` Srikar Dronamraju
2019-11-18 16:26 ` single aio thread is migrated crazily by scheduler Srikar Dronamraju
2019-11-18 21:18 ` Dave Chinner
2019-11-19 8:54 ` Ming Lei
[not found] ` <20191128094003.752-1-hdanton@sina.com>
2019-11-28 9:53 ` Vincent Guittot
2019-12-02 2:46 ` Ming Lei
2019-12-02 4:02 ` Dave Chinner
2019-12-02 4:22 ` Ming Lei
2019-12-02 13:45 ` Vincent Guittot
2019-12-02 21:22 ` Phil Auld
2019-12-03 9:45 ` Vincent Guittot
2019-12-04 13:50 ` Ming Lei
2019-12-02 23:53 ` Dave Chinner
2019-12-03 0:18 ` Ming Lei
2019-12-03 13:34 ` Vincent Guittot
2019-12-02 7:39 ` Juri Lelli
2019-12-02 3:08 ` Dave Chinner
[not found] ` <20191202090158.15016-1-hdanton@sina.com>
2019-12-02 23:06 ` Dave Chinner
[not found] ` <20191203131514.5176-1-hdanton@sina.com>
2019-12-03 22:29 ` Dave Chinner
[not found] ` <20191204102903.896-1-hdanton@sina.com>
2019-12-04 22:59 ` Dave Chinner
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