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From: Tejun Heo <tj@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Li Zefan <lizefan@huawei.com>,
	Glauber Costa <glommer@parallels.com>,
	containers@lists.linux-foundation.org, cgroups@vger.kernel.org,
	linux-kernel@vger.kernel.org, Michal Hocko <mhocko@suse.cz>,
	Paul Turner <pjt@google.com>,
	Johannes Weiner <hannes@cmpxchg.org>, Thomas Graf <tgraf@suug.ch>,
	"Serge E. Hallyn" <serue@us.ibm.com>,
	Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
	Neil Horman <nhorman@tuxdriver.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
	"Daniel P. Berrange" <berrange@redhat.com>,
	Lennart Poettering <lennart@poettering.net>,
	Kay Sievers <kay.sievers@vrfy.org>
Subject: Re: [RFC] cgroup TODOs
Date: Fri, 14 Sep 2012 11:33:16 -0700	[thread overview]
Message-ID: <20120914183316.GG17747@google.com> (raw)
In-Reply-To: <1347647021.7172.74.camel@twins>

Hello,

On Fri, Sep 14, 2012 at 08:23:41PM +0200, Peter Zijlstra wrote:
> Its hotplug, all hotplug stuff is synchronous, the last thing hotplug
> needs is the added complexity of async callbacks. Also pushing stuff out
> into worklets just to work around locking issues is vile.

I was asking whether it *has* to be part of synchronous CPU hotplug
operation.  IOW, do all tasks in the depleted cgroup have to be moved
to its parent before CPU hotunplug can proceed to completion or is it
okay to happen afterwards?  Making the migration part asynchronous
doesn't add much complexity.  The only thing you have to make sure is
flushing the previously scheduled one from the next CPU_UP_PREPARE.

Also note that this can't easily be solved by splitting tree
protecting inner lock from the outer lock.  We're talking about doing
full migration operations which likely require the outer one too.

> <handwave as I never can remember all the cgroup stuff/>
> 
> Can't we play games by pinning both cgroups with a reference and playing
> games with threadgroup_change / task_lock for the individual tasks being
> moved about?

I'm lost.  Can you please elaborate?

Thanks.

-- 
tejun

  reply	other threads:[~2012-09-14 18:33 UTC|newest]

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-09-13 20:58 [RFC] cgroup TODOs Tejun Heo
2012-09-14  9:04 ` Mike Galbraith
2012-09-14 17:17   ` Tejun Heo
2012-09-14  9:10 ` Daniel P. Berrange
2012-09-14 13:58   ` Vivek Goyal
2012-09-14 19:29     ` Tejun Heo
2012-09-14 21:51       ` Kay Sievers
     [not found] ` <5052E7DF.7040000@parallels.com>
2012-09-14  9:12   ` Li Zefan
2012-09-14 11:22     ` Peter Zijlstra
2012-09-14 17:59     ` Tejun Heo
2012-09-14 18:23       ` Peter Zijlstra
2012-09-14 18:33         ` Tejun Heo [this message]
2012-09-14 17:43   ` Tejun Heo
2012-09-17  8:50     ` Glauber Costa
2012-09-17 17:21       ` Tejun Heo
2012-09-14 11:15 ` Peter Zijlstra
2012-09-14 12:54   ` Daniel P. Berrange
2012-09-14 17:53   ` Tejun Heo
2012-09-14 14:25 ` Vivek Goyal
2012-09-14 14:53   ` Peter Zijlstra
2012-09-14 15:14     ` Vivek Goyal
2012-09-14 21:57       ` Tejun Heo
2012-09-17 15:27         ` Vivek Goyal
2012-09-18 18:08         ` Vivek Goyal
2012-09-14 21:39   ` Tejun Heo
2012-09-17 15:05     ` Vivek Goyal
2012-09-17 16:40       ` Tejun Heo
2012-09-14 15:03 ` Michal Hocko
2012-09-19 14:02   ` Michal Hocko
2012-09-19 14:03     ` [PATCH 2.6.32] memcg: warn on deeper hierarchies with use_hierarchy==0 Michal Hocko
2012-09-19 19:38       ` David Rientjes
2012-09-20 13:24         ` Michal Hocko
2012-09-20 22:33           ` David Rientjes
2012-09-21  7:16             ` Michal Hocko
2012-09-19 14:03     ` [PATCH 3.0] " Michal Hocko
2012-09-19 14:05     ` [PATCH 3.2+] " Michal Hocko
2012-09-14 18:07 ` [RFC] cgroup TODOs Vivek Goyal
2012-09-14 18:53   ` Tejun Heo
2012-09-14 19:28     ` Vivek Goyal
2012-09-14 19:44       ` Tejun Heo
2012-09-14 19:49         ` Tejun Heo
2012-09-14 20:39           ` Tejun Heo
2012-09-17  8:40             ` Glauber Costa
2012-09-17 17:30               ` Tejun Heo
2012-09-17 14:37             ` Vivek Goyal
2012-09-14 18:36 ` Aristeu Rozanski
2012-09-14 18:54   ` Tejun Heo
2012-09-15  2:20   ` Serge E. Hallyn
2012-09-15  9:27     ` Controlling devices and device namespaces Eric W. Biederman
2012-09-15 22:05       ` Serge E. Hallyn
2012-09-16  0:24         ` Eric W. Biederman
2012-09-16  3:31           ` Serge E. Hallyn
2012-09-16 11:21           ` Alan Cox
2012-09-16 11:56             ` Eric W. Biederman
2012-09-16 12:17               ` Eric W. Biederman
2012-09-16 13:32                 ` Serge Hallyn
2012-09-16 14:23                   ` Eric W. Biederman
2012-09-16 16:13                     ` Alan Cox
2012-09-16 17:49                       ` Eric W. Biederman
2012-09-16 16:15                     ` Serge Hallyn
2012-09-16 16:53                       ` Eric W. Biederman
2012-09-16  8:19   ` [RFC] cgroup TODOs James Bottomley
2012-09-16 14:41     ` Eric W. Biederman
2012-09-17 13:21     ` Aristeu Rozanski
2012-09-14 22:03 ` Dhaval Giani
2012-09-14 22:06   ` Tejun Heo
2012-09-20  1:33 ` Andy Lutomirski
2012-09-20 18:26   ` Tejun Heo
2012-09-20 18:39     ` Andy Lutomirski
2012-09-21 21:40 ` Tejun Heo

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