Add soft limits to the memory controller v2

This patchset implements the basic changes required to implement soft limits
in the memory controller. A soft limit is a variation of the currently
supported hard limit feature. A memory cgroup can exceed it's soft limit
provided there is no contention for memory.

These patches were tested on a PowerPC box, by running a programs in parallel,
and checking their behaviour for various soft limit values.

These patches were developed on top of 2.6.25-rc2-mm1. Comments, suggestions,
criticism are all welcome!

TODOs:

1. Currently there is no ordering of memory cgroups over their limit.
   We use a simple linked list to maintain a list of groups over their
   limit. In the future, we might want to create a heap of objects ordered
   by the amount by which they exceed soft limit.
2. Distribute the excessive (non-contended) resources between groups
   in the ratio of their soft limits
3. Merge with KAMEZAWA's and YAMAMOTO's water mark and background reclaim
   patches in the long-term


series
------
memory-controller-res_counters-soft-limit-setup.patch
memory-controller-add-soft-limit-interface.patch
memory-controller-reclaim-on-contention.patch
memory-controller-add-soft-limit-documentation.patch

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL