linux-toradex.git/include/linux/memcontrol.h, branch v2.6.35-rc3

memcg: fix mis-accounting of file mapped racy with migration

2010-05-27T16:12:44+00:00

FILE_MAPPED per memcg of migrated file cache is not properly updated,
because our hook in page_add_file_rmap() can't know to which memcg
FILE_MAPPED should be counted.

Basically, this patch is for fixing the bug but includes some big changes
to fix up other messes.

Now, at migrating mapped file, events happen in following sequence.

 1. allocate a new page.
 2. get memcg of an old page.
 3. charge ageinst a new page before migration. But at this point,
    no changes to new page's page_cgroup, no commit for the charge.
    (IOW, PCG_USED bit is not set.)
 4. page migration replaces radix-tree, old-page and new-page.
 5. page migration remaps the new page if the old page was mapped.
 6. Here, the new page is unlocked.
 7. memcg commits the charge for newpage, Mark the new page's page_cgroup
    as PCG_USED.

Because "commit" happens after page-remap, we can count FILE_MAPPED
at "5", because we should avoid to trust page_cgroup->mem_cgroup.
if PCG_USED bit is unset.
(Note: memcg's LRU removal code does that but LRU-isolation logic is used
 for helping it. When we overwrite page_cgroup->mem_cgroup, page_cgroup is
 not on LRU or page_cgroup->mem_cgroup is NULL.)

We can lose file_mapped accounting information at 5 because FILE_MAPPED
is updated only when mapcount changes 0->1. So we should catch it.

BTW, historically, above implemntation comes from migration-failure
of anonymous page. Because we charge both of old page and new page
with mapcount=0, we can't catch
  - the page is really freed before remap.
  - migration fails but it's freed before remap
or .....corner cases.

New migration sequence with memcg is:

 1. allocate a new page.
 2. mark PageCgroupMigration to the old page.
 3. charge against a new page onto the old page's memcg. (here, new page's pc
    is marked as PageCgroupUsed.)
 4. page migration replaces radix-tree, page table, etc...
 5. At remapping, new page's page_cgroup is now makrked as "USED"
    We can catch 0->1 event and FILE_MAPPED will be properly updated.

    And we can catch SWAPOUT event after unlock this and freeing this
    page by unmap() can be caught.

 7. Clear PageCgroupMigration of the old page.

So, FILE_MAPPED will be correctly updated.

Then, for what MIGRATION flag is ?
  Without it, at migration failure, we may have to charge old page again
  because it may be fully unmapped. "charge" means that we have to dive into
  memory reclaim or something complated. So, it's better to avoid
  charge it again. Before this patch, __commit_charge() was working for
  both of the old/new page and fixed up all. But this technique has some
  racy condtion around FILE_MAPPED and SWAPOUT etc...
  Now, the kernel use MIGRATION flag and don't uncharge old page until
  the end of migration.

I hope this change will make memcg's page migration much simpler.  This
page migration has caused several troubles.  Worth to add a flag for
simplification.

Reviewed-by: Daisuke Nishimura 
Tested-by: Daisuke Nishimura 
Reported-by: Daisuke Nishimura 
Signed-off-by: KAMEZAWA Hiroyuki 
Cc: Balbir Singh 
Cc: Christoph Lameter 
Cc: "Kirill A. Shutemov" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

vmscan: remove isolate_pages callback scan control

2010-05-25T15:07:00+00:00

For now, we have global isolation vs.  memory control group isolation, do
not allow the reclaim entry function to set an arbitrary page isolation
callback, we do not need that flexibility.

And since we already pass around the group descriptor for the memory
control group isolation case, just use it to decide which one of the two
isolator functions to use.

The decisions can be merged into nearby branches, so no extra cost there.
In fact, we save the indirect calls.

Signed-off-by: Johannes Weiner 
Cc: KOSAKI Motohiro 
Cc: Mel Gorman 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: fix oom kill behavior

2010-03-12T23:52:38+00:00

In current page-fault code,

	handle_mm_fault()
		-> ...
		-> mem_cgroup_charge()
		-> map page or handle error.
	-> check return code.

If page fault's return code is VM_FAULT_OOM, page_fault_out_of_memory() is
called.  But if it's caused by memcg, OOM should have been already
invoked.

Then, I added a patch: a636b327f731143ccc544b966cfd8de6cb6d72c6.  That
patch records last_oom_jiffies for memcg's sub-hierarchy and prevents
page_fault_out_of_memory from being invoked in near future.

But Nishimura-san reported that check by jiffies is not enough when the
system is terribly heavy.

This patch changes memcg's oom logic as.
 * If memcg causes OOM-kill, continue to retry.
 * remove jiffies check which is used now.
 * add memcg-oom-lock which works like perzone oom lock.
 * If current is killed(as a process), bypass charge.

Something more sophisticated can be added but this pactch does
fundamental things.
TODO:
 - add oom notifier
 - add permemcg disable-oom-kill flag and freezer at oom.
 - more chances for wake up oom waiter (when changing memory limit etc..)

Reviewed-by: Daisuke Nishimura 
Tested-by: Daisuke Nishimura 
Signed-off-by: KAMEZAWA Hiroyuki 
Cc: Balbir Singh 
Cc: David Rientjes 
Signed-off-by: Daisuke Nishimura 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'hwpoison' of git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6

2009-12-16T20:36:49+00:00

* 'hwpoison' of git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6: (34 commits)
  HWPOISON: Remove stray phrase in a comment
  HWPOISON: Try to allocate migration page on the same node
  HWPOISON: Don't do early filtering if filter is disabled
  HWPOISON: Add a madvise() injector for soft page offlining
  HWPOISON: Add soft page offline support
  HWPOISON: Undefine short-hand macros after use to avoid namespace conflict
  HWPOISON: Use new shake_page in memory_failure
  HWPOISON: Use correct name for MADV_HWPOISON in documentation
  HWPOISON: mention HWPoison in Kconfig entry
  HWPOISON: Use get_user_page_fast in hwpoison madvise
  HWPOISON: add an interface to switch off/on all the page filters
  HWPOISON: add memory cgroup filter
  memcg: add accessor to mem_cgroup.css
  memcg: rename and export try_get_mem_cgroup_from_page()
  HWPOISON: add page flags filter
  mm: export stable page flags
  HWPOISON: limit hwpoison injector to known page types
  HWPOISON: add fs/device filters
  HWPOISON: return 0 to indicate success reliably
  HWPOISON: make semantics of IGNORED/DELAYED clear
  ...

memcg: make memcg's file mapped consistent with global VM

2009-12-16T15:20:07+00:00

In global VM, FILE_MAPPED is used but memcg uses MAPPED_FILE.  This makes
grep difficult.  Replace memcg's MAPPED_FILE with FILE_MAPPED

And in global VM, mapped shared memory is accounted into FILE_MAPPED.
But memcg doesn't. fix it.
Note:
  page_is_file_cache() just checks SwapBacked or not.
  So, we need to check PageAnon.

Cc: Balbir Singh 
Reviewed-by: Daisuke Nishimura 
Signed-off-by: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: coalesce uncharge during unmap/truncate

2009-12-16T15:20:07+00:00

In massive parallel enviroment, res_counter can be a performance
bottleneck.  One strong techinque to reduce lock contention is reducing
calls by coalescing some amount of calls into one.

Considering charge/uncharge chatacteristic,
	- charge is done one by one via demand-paging.
	- uncharge is done by
		- in chunk at munmap, truncate, exit, execve...
		- one by one via vmscan/paging.

It seems we have a chance to coalesce uncharges for improving scalability
at unmap/truncation.

This patch is a for coalescing uncharge.  For avoiding scattering memcg's
structure to functions under /mm, this patch adds memcg batch uncharge
information to the task.  A reason for per-task batching is for making use
of caller's context information.  We do batched uncharge (deleyed
uncharge) when truncation/unmap occurs but do direct uncharge when
uncharge is called by memory reclaim (vmscan.c).

The degree of coalescing depends on callers
  - at invalidate/trucate... pagevec size
  - at unmap ....ZAP_BLOCK_SIZE
(memory itself will be freed in this degree.)
Then, we'll not coalescing too much.

On x86-64 8cpu server, I tested overheads of memcg at page fault by
running a program which does map/fault/unmap in a loop. Running
a task per a cpu by taskset and see sum of the number of page faults
in 60secs.

[without memcg config]
  40156968  page-faults              #      0.085 M/sec   ( +-   0.046% )
  27.67 cache-miss/faults
[root cgroup]
  36659599  page-faults              #      0.077 M/sec   ( +-   0.247% )
  31.58 miss/faults
[in a child cgroup]
  18444157  page-faults              #      0.039 M/sec   ( +-   0.133% )
  69.96 miss/faults
[child with this patch]
  27133719  page-faults              #      0.057 M/sec   ( +-   0.155% )
  47.16 miss/faults

We can see some amounts of improvement.
(root cgroup doesn't affected by this patch)
Another patch for "charge" will follow this and above will be improved more.

Changelog(since 2009/10/02):
 - renamed filed of memcg_batch (as pages to bytes, memsw to memsw_bytes)
 - some clean up and commentary/description updates.
 - added initialize code to copy_process(). (possible bug fix)

Changelog(old):
 - fixed !CONFIG_MEM_CGROUP case.
 - rebased onto the latest mmotm + softlimit fix patches.
 - unified patch for callers
 - added commetns.
 - make ->do_batch as bool.
 - removed css_get() at el. We don't need it.

Signed-off-by: KAMEZAWA Hiroyuki 
Cc: Balbir Singh 
Cc: Daisuke Nishimura 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: add accessor to mem_cgroup.css

2009-12-16T11:19:59+00:00

So that an outside user can free the reference count grabbed by
try_get_mem_cgroup_from_page().

CC: KOSAKI Motohiro 
CC: Hugh Dickins 
CC: Daisuke Nishimura 
CC: Balbir Singh 
Acked-by: KAMEZAWA Hiroyuki 
Signed-off-by: Wu Fengguang 
Signed-off-by: Andi Kleen

memcg: rename and export try_get_mem_cgroup_from_page()

2009-12-16T11:19:59+00:00

So that the hwpoison injector can get mem_cgroup for arbitrary page
and thus know whether it is owned by some mem_cgroup task(s).

[AK: Merged with latest git tree]

CC: KOSAKI Motohiro 
CC: Hugh Dickins 
CC: Daisuke Nishimura 
CC: Balbir Singh 
Acked-by: KAMEZAWA Hiroyuki 
Signed-off-by: Wu Fengguang 
Signed-off-by: Andi Kleen

memory controller: soft limit reclaim on contention

2009-09-24T14:20:59+00:00

Implement reclaim from groups over their soft limit

Permit reclaim from memory cgroups on contention (via the direct reclaim
path).

memory cgroup soft limit reclaim finds the group that exceeds its soft
limit by the largest number of pages and reclaims pages from it and then
reinserts the cgroup into its correct place in the rbtree.

Add additional checks to mem_cgroup_hierarchical_reclaim() to detect long
loops in case all swap is turned off.  The code has been refactored and
the loop check (loop < 2) has been enhanced for soft limits.  For soft
limits, we try to do more targetted reclaim.  Instead of bailing out after
two loops, the routine now reclaims memory proportional to the size by
which the soft limit is exceeded.  The proportion has been empirically
determined.

[akpm@linux-foundation.org: build fix]
[kamezawa.hiroyu@jp.fujitsu.com: fix softlimit css refcnt handling]
[nishimura@mxp.nes.nec.co.jp: refcount of the "victim" should be decremented before exiting the loop]
Signed-off-by: Balbir Singh 
Cc: KAMEZAWA Hiroyuki 
Cc: Li Zefan 
Acked-by: KOSAKI Motohiro 
Signed-off-by: KAMEZAWA Hiroyuki 
Signed-off-by: Daisuke Nishimura 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: add file-based RSS accounting

2009-06-18T20:03:47+00:00

Add file RSS tracking per memory cgroup

We currently don't track file RSS, the RSS we report is actually anon RSS.
 All the file mapped pages, come in through the page cache and get
accounted there.  This patch adds support for accounting file RSS pages.
It should

1. Help improve the metrics reported by the memory resource controller
2. Will form the basis for a future shared memory accounting heuristic
   that has been proposed by Kamezawa.

Unfortunately, we cannot rename the existing "rss" keyword used in
memory.stat to "anon_rss".  We however, add "mapped_file" data and hope to
educate the end user through documentation.

[hugh.dickins@tiscali.co.uk: fix mem_cgroup_update_mapped_file_stat oops]
Signed-off-by: Balbir Singh 
Acked-by: KAMEZAWA Hiroyuki 
Cc: Li Zefan 
Cc: Paul Menage 
Cc: Dhaval Giani 
Cc: Daisuke Nishimura 
Cc: YAMAMOTO Takashi 
Cc: KOSAKI Motohiro 
Cc: David Rientjes 
Signed-off-by: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds