linux-kernel - Re: [RFC 0/3] Implementation of cgroup isolation

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Date:	Fri, 1 Apr 2011 16:04:46 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Ying Han <yinghan@...gle.com>
Cc:	Balbir Singh <bsingharora@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 0/3] Implementation of cgroup isolation

On Thu 31-03-11 11:10:00, Ying Han wrote:
> On Thu, Mar 31, 2011 at 2:53 AM, Michal Hocko <mhocko@...e.cz> wrote:
> > On Wed 30-03-11 10:59:21, Ying Han wrote:
[...]
> > That was my concern so I made that isolation rather opt-in without
> > modifying the current reclaim logic too much (there are, of course,
> > parts that can be improved).
> 
> So far we are discussing the memory limit only for user pages. Later
> we definitely need a kernel memory slab accounting and also for
> reclaim. If we put them together, do you still have the concern? Sorry
> guess I am just trying to understand the concern w/ example.

If we account the kernel memory then it should be less problematic, I
guess.

[...]
> > Lots of groups is really an issue because we can end up in a situation
> > when everybody is under the limit while there is not much memory left
> > for the kernel. Maybe sum(soft_limit) < kernel_treshold condition would
> > solve this.
> most of the kernel memory are allocated on behalf of processes in
> cgroup. One way of doing that (after having kernel memory accounting)
> is to count in kernel memory into usage_in_bytes. So we have the
> following:
> 
> 1) limit_in_bytes: cap of memory allocation (user + kernel) for cgroup-A
> 2) soft_limit_in_bytes: guarantee of memory allocation  (user +
> kernel) for cgroup-A
> 3) usage_in_bytes: user pages + kernel pages (allocated on behalf of the memcg)
> 
> The above need kernel memory accounting and targeting reclaim. Then we
> have sum(soft_limit) < machine capacity. Hope we can talk a bit in the
> LSF on this too.

Sure. I am looking forward.

> >> The later one breaks the isolation.
> >
> > Sorry, I don't understand. Why would elimination of the global lru
> > scanning break isolation? Or am I misreading you?
> 
> Sorry, i meant the other way around. So we agree on this .

Makes more sense now ;)

Thanks
-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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