From: Yong Zhang <yong.zhang0@gmail.com>
To: Lin Ming <ming.m.lin@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
"mingo@elte.hu" <mingo@elte.hu>,
lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] sched: Remove WAKEUP_PREEMPT feature check in entity_tick
Date: Fri, 29 Jul 2011 15:46:35 +0800 [thread overview]
Message-ID: <20110729074635.GB10420@zhy> (raw)
In-Reply-To: <1311924975.3938.1583.camel@minggr.sh.intel.com>
On Fri, Jul 29, 2011 at 03:36:15PM +0800, Lin Ming wrote:
> >From another point of view, below !sched_feat(WAKEUP_PREEMPT) still
> looks like duplicated.
>
> if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
> check_preempt_tick(cfs_rq, curr);
>
> if "!sched_feat(WAKEUP_PREEMPT)" is run,
> that implies cfs_rq->nr_running == 1.
That's true.
>
> Why do we need to call check_preempt_tick when there is only 1 task
> runnable?
Just set_tsk_need_resched(p) if p's slice is over, thus:
(n tick) ---> (n+1 tick)
set_tsk_need_resched(p);
another task Q is awaked
If we don't have !sched_feat(WAKEUP_PREEMPT), Q maybe will wait
for tick coming to get scheduled. If we have
!sched_feat(WAKEUP_PREEMPT), Q will get scheduled when some event
happen, like IRQ.
Thanks,
Yong
--
Only stand for myself
next prev parent reply other threads:[~2011-07-29 7:46 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-28 9:43 [PATCH] sched: Remove WAKEUP_PREEMPT feature check in entity_tick Lin Ming
2011-07-29 6:21 ` Yong Zhang
2011-07-29 6:24 ` Yong Zhang
2011-07-29 6:49 ` Lin Ming
2011-07-29 7:03 ` Yong Zhang
2011-07-29 7:36 ` Lin Ming
2011-07-29 7:46 ` Yong Zhang [this message]
2011-07-29 7:56 ` Lin Ming
2011-07-29 7:56 ` Peter Zijlstra
2011-07-29 8:18 ` Yong Zhang
2011-07-29 8:20 ` Peter Zijlstra
2011-07-29 8:44 ` Lin Ming
2011-07-29 8:46 ` Yong Zhang
2011-07-29 11:45 ` Peter Zijlstra
2011-08-01 1:33 ` Yong Zhang
2011-07-29 8:20 ` [RFC PATCH] sched: Kill WAKEUP_PREEMPT Yong Zhang
2011-07-29 8:30 ` Lin Ming
2011-07-29 8:32 ` Lin Ming
2011-08-14 15:57 ` [tip:sched/core] " tip-bot for Yong Zhang
2011-07-29 9:04 ` [PATCH] sched: Remove WAKEUP_PREEMPT feature check in entity_tick Mike Galbraith
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