linux-kernel - Re: [PATCH 0/2] CGroups: cgroup member list enhancement/fix

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Date:	Mon, 13 Jul 2009 17:41:38 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Paul Menage <menage@...gle.com>
Cc:	lizf@...fujitzu.com, bblum@...gle.com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	containers@...ts.linux-foundation.org,
	libcg-devel <libcg-devel@...ts.sourceforge.net>
Subject: Re: [PATCH 0/2] CGroups: cgroup member list enhancement/fix

* menage@...gle.com <menage@...gle.com> [2009-07-10 16:58:23]:

> On Sat, Jul 4, 2009 at 11:38 PM, Balbir Singh<balbir@...ux.vnet.ibm.com> wrote:
> >
> > Paul, I don't see an interface to migrate all procs or at-least I
> > can't read it in the changelog. As discussed in the containers
> > mini-summit in 2008, it would be a nice thing to have (I've not looked
> > at the implementation yet).
> >
> 
> We're still working on that bit.
> 
> We want to provide the guarantee that if you write a tgid to the procs
> file, all its threads get migrated even if you race with a clone()
> call, and are trying to figure out a nice way to do that without
> introducing unnecessary overhead/synchronization in the fork path.
>

How about lazy migration? Mark a group as to move when the kernel sees
it next for scheduling. We'll still need synchronization, but we can
amortize the cost. I've not tried it yet. BTW, we have quite a bit of
logic in libcgroup to deal with migration problems, specially during
classification, which Kenichi has added. We needed timestamping to get
correct migration working during classification.

-- 
	Balbir
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