BC: resource beancounters (v6) (with userpages reclamation + configfs)

[Kirill Korotaev]

MAJOR CHANGES in v6 (see details below):
- configfs interface instead of syscalls (as wanted by CKRM people...)
- added numfiles resource accounting
- added numtasks resource accounting

numfiles and numtasks controllers demonstrate how
clean and simple BC interface is.

Patch set is applicable to 2.6.19-rc5-mm1

-----------------------------------------------------

Resource BeanCounters (BC).

BC allows to account and control consumption
of kernel resources used by *group* of processes
(users, containers, ...).

Draft BC description on OpenVZ wiki can be found at
http://wiki.openvz.org/UBC_parameters

The full BC patch set allows to control:
- kernel memory. All the kernel objects allocatable
on user demand and not reclaimable should be accounted and
limited for DoS protection.
e.g. page tables, task structs, vmas etc.

- virtual memory pages. BCs allow to
limit a container to some amount of memory and
introduces 2-level OOM killer taking into account
container's consumption.
pages shared between containers are correctly
charged as fractions (tunable).

- network buffers. These includes TCP/IP rcv/snd
buffers, dgram snd buffers, unix, netlinks and
other buffers.

- minor resources accounted/limited by number:
tasks, files, flocks, ptys, siginfo, pinned dcache
mem, sockets, iptentries (for containers with
virtualized networking)

Summary of changes from v5 patch set:
* configfs interface instead of syscalls (as wanted by CKRM people)
* added numfiles resource accounting
* added numtasks resource accounting
* introduced dummy_resource to handle case when
  no resource registered
* calls to rss accounting are integrated to rmap calls

Summary of changes from v4 patch set:
* changed set of resources - kmemsize, privvmpages, physpages
* added event hooks for resources (init, limit hit etc)
* added user pages reclamation (bc_try_to_free_pages)
* removed pages sharing accounting - charge to first user
* task now carries only one BC pointer, simplified
* make set_bcid syscall move arbitrary task into BC
* resources are not recharged when task moves
* each vm_area_struct carries a BC pointer

Summary of changes from v3 patch set:

* Added basic user pages accounting (lockedpages/privvmpages)
* spell in Kconfig
* Makefile reworked
* EXPORT_SYMBOL_GPL
* union w/o name in struct page
* bc_task_charge is void now
* adjust minheld/maxheld splitted

Summary of changes from v2 patch set:

* introduced atomic_dec_and_lock_irqsave()
* bc_adjust_held_minmax comment
* added __must_check for bc_*charge* funcs
* use hash_long() instead of own one
* bc/Kconfig is sourced from init/Kconfig now
* introduced bcid_t type with comment from Alan Cox
* check for barrier <= limit in sys_set_bclimit()
* removed (bc == NULL) checks
* replaced memcpy in beancounter_findcrate with assignment
* moved check 'if (mask & BC_ALLOC)' out of the lock
* removed unnecessary memset()

Summary of changes from v1 patch set:

* CONFIG_BEANCOUNTERS is 'n' by default
* fixed Kconfig includes in arches
* removed hierarchical beancounters to simplify first patchset
* removed unused 'private' pointer
* removed unused EXPORTS
* MAXVALUE redeclared as LONG_MAX
* beancounter_findcreate clarification
* renamed UBC -> BC, ub -> bc etc.
* moved BC inheritance into copy_process
* introduced reset_exec_bc() with proposed BUG_ON
* removed task_bc beancounter (not used yet, for numproc)
* fixed syscalls for sparc
* added sys_get_bcstat(): return info that was in /proc
* cond_syscall instead of #ifdefs

Many thanks to Oleg Nesterov, Alan Cox, Matt Helsley and others
for patch review and comments.

Thanks,
Kirill
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