From: Wanpeng Li <wanpeng.li@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>, Juri Lelli <juri.lelli@arm.com>
Cc: Wanpeng Li <wanpeng.li@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>,
Kirill Tkhai <ktkhai@parallels.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] sched/deadline: support dl task migration during cpu hotplug
Date: Tue, 6 Jan 2015 10:14:58 +0800 [thread overview]
Message-ID: <20150106021458.GA24813@kernel> (raw)
In-Reply-To: <20150105145210.GO10476@twins.programming.kicks-ass.net>
Hi Peter,
On Mon, Jan 05, 2015 at 03:52:10PM +0100, Peter Zijlstra wrote:
>On Wed, Nov 12, 2014 at 04:39:06PM +0100, Peter Zijlstra wrote:
>> On Wed, Nov 12, 2014 at 03:08:44PM +0000, Juri Lelli wrote:
>> > > @@ -1185,8 +1223,9 @@ static int find_later_rq(struct task_struct *task)
>> > > * We have to consider system topology and task affinity
>> > > * first, then we can look for a suitable cpu.
>> > > */
>> > > - cpumask_copy(later_mask, task_rq(task)->rd->span);
>> > > - cpumask_and(later_mask, later_mask, cpu_active_mask);
>> > > + cpumask_copy(later_mask, cpu_active_mask);
>> > > + if (likely(task_rq(task)->online))
>> > > + cpumask_and(later_mask, later_mask, task_rq(task)->rd->span);
>> >
>> > So, here you consider the span only when the task_rq is online,
>> > but there might be others cpus still online belonging to the same
>> > rd->span. And you have to consider them when migrating. Actually,
>> > migration must still be restricted to the online cpus of task's
>> > original rd->span, or I fear you can break clustered scheduling.
>>
>> Ah, good point that, we must somehow find the right root domain to
>> 'restore' the task to. Now I'm not entirely sure we still have this.
>> Lemme ponder that.
>
>Ah, we should be able to find this by looking at the cpuset cgroup
>information. The cpuset cgroup knows the available cpumask of this task,
>which we can translate to the correct root domain in two separate ways
>(either run up the cpuset cgroup hierarchy and find the highest domain
>with balancing enabled, or look at whatever the rq->rd is for any one of
>the allowed CPUs of the immediate cgroup this task belongs to).
If the patch Juri pointed out can help to skip the issue?
https://lkml.org/lkml/2014/11/19/293
Regards,
Wanpeng Li
next prev parent reply other threads:[~2015-01-06 2:34 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-12 1:06 [PATCH v5] sched/deadline: support dl task migration during cpu hotplug Wanpeng Li
2014-11-12 15:08 ` Juri Lelli
2014-11-12 15:39 ` Peter Zijlstra
2014-11-12 23:02 ` Wanpeng Li
2015-01-05 14:52 ` Peter Zijlstra
2015-01-06 2:14 ` Wanpeng Li [this message]
2014-11-12 23:22 ` Wanpeng Li
2014-11-18 23:18 ` Wanpeng Li
2014-11-19 10:13 ` Juri Lelli
2014-11-19 12:30 ` Wanpeng Li
2014-11-19 13:49 ` Juri Lelli
2014-11-19 23:08 ` Wanpeng Li
2014-11-12 16:27 ` Kirill Tkhai
2014-11-12 22:56 ` Wanpeng Li
2014-11-13 10:10 ` Kirill Tkhai
2014-11-13 10:19 ` Wanpeng Li
2014-11-13 10:21 ` Kirill Tkhai
2014-11-16 22:59 ` Wanpeng Li
2014-11-20 8:49 ` Wanpeng Li
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