[Devel] Re: [ckrm-tech] containers development plans (July 10 version)

[Dave Hansen]

On Wed, 2007-07-11 at 21:18 +0900, Takenori Nagano wrote:
> I think Balbir's idea is very simple and reasonable way to develop per container
> swapping. Because kernel needs the information that a target page belongs to
> which container. Fortunately, we already had page based memory management system
> which included in RSS controller. I think it is appropriate that we develop per
> container swapping on page based memory management system. 

There are a couple of concepts being thrown about here, so let's
separate them out a bit.

1. Limit a container's usage of swap.
   - Keep track of how many swap pages a container uses
   - go OOM on the container when it exceeds its allowed usage
   - tracking will be on a container's use of swap globally, no matter
     what swap device or file it is actually allocated in
   - all containers share all swapfiles
2. Keep separate lists of swap devices for each container
   - each container is allowed to use a subset of the system's
     swap files
   eventually:
   - keep a per-container list of which pte values correspond
     to which swapfiles
   - pte swap values are only valid inside of one container
3. Use a completely isolated set of swapfiles from (2) for 
   checkpoint/restart
   - ensures that any swapfile will only contain data from one container

The idea in (1) is not very useful for checkpoint/restart, but it would
be useful to solve the cpuset OOM problem described in the VM BOF.  
( That problem is basically that a cpuset with available memory but a
  large amount in swap can cause another cpuset to go OOM.  The memory
  footprint in the system is under RAM+swap, but the OOM still happens.)

-- Dave

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