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Subject[PATCH] BC: resource beancounters (v5) (added userpages reclamation)
- phys pages limit hit leads to user pages reclamation
- bc can be changed on arbitrary task

Core Resource Beancounters (BC) + kernel/user memory control.

BC allows to account and control consumption
of kernel resources used by group of processes.

Draft UBC description on OpenVZ wiki can be found at

The full BC patch set allows to control:
- kernel memory. All the kernel objects allocatable
on user demand 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)

As the first step we want to propose for discussion
the most complicated parts of resource management:
kernel memory and virtual memory.
The patch set to be sent provides core for BC and
management of kernel memory only. Virtual memory
management will be sent in a couple of days.

The patches in these series are:
* diff-atomic-dec-and-lock-irqsave.patch:
introduce atomic_dec_and_lock_irqsave()

* diff-bc-kconfig.patch:
Adds kernel/bc/Kconfig file with UBC options and
includes it into arch Kconfigs

* diff-bc-core.patch:
Contains core functionality and interfaces of BC:
find/create beancounter, initialization,
charge/uncharge of resource, core objects' declarations.

* diff-bc-task.patch:
Contains code responsible for setting BC on task,
it's inheriting and setting host context in interrupts.

* diff-bc-syscalls.patch:
Patch adds system calls for BC management:
1. sys_get_bcid - get current BC id
2. sys_set_bcid - changes BC on task
3. sys_set_bclimit - set limits for resources consumtions
4. sys_get_bcstat - returns limits/usages/fails for BC

* diff-bc-kmem-core.patch:
Introduces BC_KMEMSIZE resource which accounts kernel
objects allocated by task's request.

Objects are accounted via struct page and slab objects.
For the latter ones each slab contains a set of pointers
corresponding object is charged to.

Allocation charge rules:
1. Pages - if allocation is performed with __GFP_BC flag - page
is charged to current's exec_bc.
2. Slabs - kmem_cache may be created with SLAB_BC flag - in this
case each allocation is charged. Caches used by kmalloc are
created with SLAB_BC | SLAB_BC_NOCHARGE flags. In this case
only __GFP_BC allocations are charged.
* diff-bc-kmem-charge.patch:
Adds SLAB_BC and __GFP_BC flags in appropriate places
to cause charging/limiting of specified resources.

* diff-bc-vmpages-core:
Accounting of private pages (mappings), done per-vma.
Charged on mmap().

* diff-bc-rsspages-core:
Phys pages accounting. Charging is done on page touch
(page fault) and limit hit leads to reclamation.
Reclamation is done based on beancounter list of pages.

* diff-bc-userpages-charge:
Hooks across the kernel for user pages accounting.

* bcctl.c:
Tool for BC management. Allows changing BC, setting BC limits,
viewing current usages.

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
* 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.

Patch set is applicable to 2.6.18-mm3

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