RFC Containers: Pagecache accounting and control subsystem (v1)

Containers: Pagecache accounting and control subsystem (v1)
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This patch adds pagecache accounting and control on top of Paul's container subsystem v7 posted at
http://lkml.org/lkml/2007/2/12/88

and Balbir's RSS controller posted at
http://lkml.org/lkml/2007/2/26/8

This patchset depends on Balbir's RSS controller and cannot work independent of it. The page reclaim code has been merged with container RSS controller. However compile time options can individually enable/disable memory controller and/or pagecache controller.

Comments, suggestions and criticisms are welcome.

Features:
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* New subsystem called 'pagecache_acct' is registered with containers
* Container pointer is added to struct address_space to keep track of associated container
* In filemap.c and swap_state.c, the corresponding container's pagecache_acct subsystem is charged and uncharged whenever a new page is added or removed from pagecache
* The accounting number include pages in swap cache and filesystem buffer pages apart from pagecache, basically everything under NR_FILE_PAGES is counted as pagecache. However this excluded mapped and anonymous pages
* Limits on pagecache can be set by echo 100000 > pagecache_limit on the /container file system. The unit is in kilobytes
* If the pagecache utilisation limit is exceeded, pagecache reclaim code is invoked to recover dirty and clean pagecache pages only.

Advantages:
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* Does not add container pointers in struct page

Limitations:
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* Code is not safe for container deletion/task migration
* Pagecache page reclaim needs performance improvements
* Global LRU is churned in search of pagecache pages

Usage:
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* Add patch on top of Paul container (v7) at kernel version 2.6.20
* Enable CONFIG_CONTAINER_PAGECACHE_ACCT in 'General Setup'
* Boot new kernel
* Mount container filesystem
mount -t container /container
cd /container
* Create new container
mkdir mybox
cd /container/mybox
* Add current shell to container
echo $$ > tasks
* There are two files pagecache_usage and pagecache_limit
* In order to set limit, echo value in kilobytes to pagecache_limit

	echo 100000 > pagecache_limit
	#This would set 100MB limit on pagecache usage

* Trash the system from current shell using scp/cp/dd/tar etc
* Watch pagecache_usage and /proc/meminfo to verify behavior

* Only unmapped pagecache data will be accounted and controlled. These are memory used by cp, scp, tar etc. While file mmap will be controlled by Balbir's RSS controller.

Tests:
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* Ran kernbench within container with pagecache_limits set

ToDo:
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* Merge with container RSS controller and eliminate redundant code
* Test and support task migration and container deletion
* Review reclaim performance
* Optimise page reclaim

Patch Series:
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pagecache-controller-setup.patch
pagecache-controller-acct.patch
pagecache-controller-reclaim.patch

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