Re: [ckrm-tech] [patch00/05]: Containers(V2)- Introduction

From: Rohit Seth
Date: Thu Sep 28 2006 - 14:32:00 EST

On Thu, 2006-09-28 at 13:31 +0530, Balbir Singh wrote:
> Chandra Seetharaman wrote:
> > On Wed, 2006-09-27 at 14:28 -0700, Rohit Seth wrote:
> >
> > Rohit,
> >
> > For 1-4, I understand the rationale. But, your implementation deviates
> > from the current behavior of the VM subsystem which could affect the
> > ability of these patches getting into mainline.
> >
> > IMO, the current behavior in terms of reclamation, LRU, vm_swappiness,
> > and writeback logic should be maintained.
> >
> <snip>
> Hi, Rohit,
> I have been playing around with the containers patch. I finally got
> around to reading the code.
> 1. Comments on reclaiming
> You could try the following options to overcome some of the disadvantages of the
> current scheme.
> (a) You could consider a reclaim path based on Dave Hansen's Challenged memory
> controller (see

I will go through that. Did you get a chance to stress the system and
found any short comings that should be resolved.

> (b) The other option is to do what the resource group memory controller does -
> build a per group LRU list of pages (active, inactive) and reclaim
> them using the existing code (by passing the correct container pointer,
> instead of the zone pointer). One disadvantage of this approach is that
> the global reclaim is impacted as the global LRU list is broken. At the
> expense of another list, we could maintain two lists, global LRU and
> container LRU lists. Depending on the context of the reclaim - (container
> over limit, memory pressure) we could update/manipulate both lists.
> This approach is definitely very expensive.

Two LRUs is a nice idea. Though I don't think it will go too far. It
will involve adding another list pointers in the page structure. I
agree that the mem handler is not optimal at all but I don't want to
make it mimic kernel reclaimer at the same time.

> 2. Comments on task migration support
> (a) One of the issues I found while using the container code is that, one could
> add a task to a container say "a". "a" gets charged for the tasks usage,
> when the same task moves to a different container say "b", when the task
> exits, the credit goes to "b" and "a" remains indefinitely charged.
hmm, when the task is removed from "a" then "a" gets the credits for the
amount of anon memory that is used by the task. Or do you mean
something different.

> (b) For tasks addition and removal, I think it's probably better to move
> the entire process (thread group) rather than allow each individual thread
> to move across containers. Having threads belonging to the same process
> reside in different containers can be complex to handle, since they
> share the same VM. Do you have a scenario where the above condition
> would be useful?
I don't have a scenario where a task actually gets to move out of
container (except exit). That asynchronous removal of tasks has already
got the code very complicated for locking etc. But if you think moving
a thread group is useful then I will add that functionality.


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