Re: [rfc patch 0/6] mm: memcg naturalization

[Ying Han <yinghan@google.com>]

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On Tue, May 17, 2011 at 1:11 AM, Johannes Weiner <hannes@cmpxchg.org> wrote:

> On Mon, May 16, 2011 at 05:53:04PM -0700, Ying Han wrote:
> > On Fri, May 13, 2011 at 12:20 AM, Johannes Weiner <hannes@cmpxchg.org
> >wrote:
> >
> > > On Thu, May 12, 2011 at 11:53:37AM -0700, Ying Han wrote:
> > > > On Thu, May 12, 2011 at 7:53 AM, Johannes Weiner <hannes@cmpxchg.org
> >
> > > wrote:
> > > >
> > > > > Hi!
> > > > >
> > > > > Here is a patch series that is a result of the memcg discussions on
> > > > > LSF (memcg-aware global reclaim, global lru removal, struct
> > > > > page_cgroup reduction, soft limit implementation) and the recent
> > > > > feature discussions on linux-mm.
> > > > >
> > > > > The long-term idea is to have memcgs no longer bolted to the side
> of
> > > > > the mm code, but integrate it as much as possible such that there
> is a
> > > > > native understanding of containers, and that the traditional !memcg
> > > > > setup is just a singular group.  This series is an approach in that
> > > > > direction.
> > >
> >
> > This sounds like a good long term plan. Now I would wonder should we take
> it
> > step by step by doing:
> >
> > 1. improving the existing soft_limit reclaim from RB-tree based to
> link-list
> > based, also in a round_robin fashion.
> > We can keep the existing APIs but only changing the underlying
> > implementation of  mem_cgroup_soft_limit_reclaim()
> >
> > 2. remove the global lru list after the first one being proved to be
> > efficient.
> >
> > 3. then have better integration of memcg reclaim to the mm code.
>
> I chose to go the other because it did not seem more complex to me and
> fixed many things we had planned anyway.  Deeper integration, better
> soft limit implementation (including better pressure distribution,
> enforcement also from direct reclaim, not just kswapd), global lru removal
> etc.


> That ground work was a bit unwieldy and I think quite some confusion
> ensued, but I am currently reorganizing, cleaning up, and documenting.
> I expect the next version to be much easier to understand.
>
> The three steps are still this:
>
> 1. make traditional reclaim memcg-aware.
>
> 2. improve soft limit based on 1.
>

I don't see the soft_limit round-robin implementation on the patch 6/6,
maybe I missed it somewhere. I have my patch posted which does the
linked-list
round-robin across memcgs per-zone , do you have plan to merge them together
?

>
> 3. remove global lru based on 1.
>


>
> But 1. already effectively disables the global LRU for memcg-enabled
> kernels, so 3. can be deferred until we are comfortable with 1.
>
> Thank you for the details and clarification, and looking forward to your
next post.

--Ying

>        Hannes
>

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