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

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Date:	Mon, 28 Mar 2011 21:03:46 -0700
From:	Ying Han <yinghan@...gle.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
	Suleiman Souhlal <suleiman@...gle.com>
Subject: Re: [RFC 0/3] Implementation of cgroup isolation

On Mon, Mar 28, 2011 at 7:45 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@...fujitsu.com> wrote:
> On Mon, 28 Mar 2011 19:46:41 -0700
> Ying Han <yinghan@...gle.com> wrote:
>
>> On Mon, Mar 28, 2011 at 5:47 PM, KAMEZAWA Hiroyuki
>> <kamezawa.hiroyu@...fujitsu.com> wrote:
>
>> >
>> >> By saying that, memcg simplified the memory accounting per-cgroup but
>> >> the memory isolation is broken. This is one of examples where pages
>> >> are shared between global LRU and per-memcg LRU. It is easy to get
>> >> cgroup-A's page evicted by adding memory pressure to cgroup-B.
>> >>
>> > If you overcommit....Right ?
>>
>> yes, we want to support the configuration of over-committing the
>> machine w/ limit_in_bytes.
>>
>
> Then, soft_limit is a feature for fixing the problem. If you have problem
> with soft_limit, let's fix it.

The current implementation of soft_limit works as best-effort and some
improvement are needed. Without distracting much from this thread,
simply saying it is not optimized on which cgroup to pick from the
per-zone RB-tree.

>
>
>> >
>> >
>> >> The approach we are thinking to make the page->lru exclusive solve the
>> >> problem. and also we should be able to break the zone->lru_lock
>> >> sharing.
>> >>
>> > Is zone->lru_lock is a problem even with the help of pagevecs ?
>>
>> > If LRU management guys acks you to isolate LRUs and to make kswapd etc..
>> > more complex, okay, we'll go that way.
>>
>> I would assume the change only apply to memcg users , otherwise
>> everything is leaving in the global LRU list.
>>
>> This will _change_ the whole memcg design and concepts Maybe memcg
>> should have some kind of balloon driver to
>> > work happy with isolated lru.
>>
>> We have soft_limit hierarchical reclaim for system memory pressure,
>> and also we will add per-memcg background reclaim. Both of them do
>> targeting reclaim on per-memcg LRUs, and where is the balloon driver
>> needed?
>>
>
> If soft_limit is _not_ enough. And I think you background reclaim should
> be work with soft_limit and be triggered by global memory pressure.

This is something i can think about. Also i think we agree that we
should have efficient target reclaim
so the global LRU scanning should be eliminated.

>
> As wrote in other mail, it's not called via direct reclaim.
> Maybe its the 1st point to be shooted rather than trying big change.

Agree on this.

--Ying

>
>
>
>
> Thanks,
> -Kame
>
>
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