linux-kernel - Re: [PATCH v4 7/7] cpuset: fix to migrate mm correctly in a corner case

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Message-ID: <20130613175239.GB10799@mtj.dyndns.org>
Date:	Thu, 13 Jun 2013 10:52:39 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizefan@...wei.com>
Cc:	Cgroups <cgroups@...r.kernel.org>,
	Containers <containers@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 7/7] cpuset: fix to migrate mm correctly in a corner
 case

On Thu, Jun 13, 2013 at 03:11:44PM +0800, Li Zefan wrote:
> Before moving tasks out of empty cpusets, update_tasks_nodemask()
> is called, which calls do_migrate_pages(xx, from, to). Then those
> tasks are moved to an ancestor, and do_migrate_pages() is called
> again.
> 
> The first time: from = node_to_be_offlined, to = empty.
> The second time: from = empty, to = ancestor's nodemask.
> 
> so looks like no pages will be migrated.
> 
> Fix this by:
> 
> - Don't call update_tasks_nodemask() on empty cpusets.
> - Pass cs->old_mems_allowed to do_migrate_pages().
> 
> v4: added comment in cpuset_hotplug_update_tasks() and rephased comment
>     in cpuset_attach().
> 
> Signed-off-by: Li Zefan <lizefan@...wei.com>

Replaced v3 with this one in cgroup/for-3.11-cpuset.  Thanks!

-- 
tejun
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