linux-toradex.git/mm/memcontrol.c, branch v3.7

memcg: fix hotplugged memory zone oops

2012-11-16T22:33:04+00:00

When MEMCG is configured on (even when it's disabled by boot option),
when adding or removing a page to/from its lru list, the zone pointer
used for stats updates is nowadays taken from the struct lruvec.  (On
many configurations, calculating zone from page is slower.)

But we have no code to update all the lruvecs (per zone, per memcg) when
a memory node is hotadded.  Here's an extract from the oops which
results when running numactl to bind a program to a newly onlined node:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000f60
  IP:  __mod_zone_page_state+0x9/0x60
  Pid: 1219, comm: numactl Not tainted 3.6.0-rc5+ #180 Bochs Bochs
  Process numactl (pid: 1219, threadinfo ffff880039abc000, task ffff8800383c4ce0)
  Call Trace:
    __pagevec_lru_add_fn+0xdf/0x140
    pagevec_lru_move_fn+0xb1/0x100
    __pagevec_lru_add+0x1c/0x30
    lru_add_drain_cpu+0xa3/0x130
    lru_add_drain+0x2f/0x40
   ...

The natural solution might be to use a memcg callback whenever memory is
hotadded; but that solution has not been scoped out, and it happens that
we do have an easy location at which to update lruvec->zone.  The lruvec
pointer is discovered either by mem_cgroup_zone_lruvec() or by
mem_cgroup_page_lruvec(), and both of those do know the right zone.

So check and set lruvec->zone in those; and remove the inadequate
attempt to set lruvec->zone from lruvec_init(), which is called before
NODE_DATA(node) has been allocated in such cases.

Ah, there was one exceptionr.  For no particularly good reason,
mem_cgroup_force_empty_list() has its own code for deciding lruvec.
Change it to use the standard mem_cgroup_zone_lruvec() and
mem_cgroup_get_lru_size() too.  In fact it was already safe against such
an oops (the lru lists in danger could only be empty), but we're better
proofed against future changes this way.

I've marked this for stable (3.6) since we introduced the problem in 3.5
(now closed to stable); but I have no idea if this is the only fix
needed to get memory hotadd working with memcg in 3.6, and received no
answer when I enquired twice before.

Reported-by: Tang Chen 
Signed-off-by: Hugh Dickins 
Acked-by: Johannes Weiner 
Acked-by: KAMEZAWA Hiroyuki 
Cc: Konstantin Khlebnikov 
Cc: Wen Congyang 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: oom: fix totalpages calculation for memory.swappiness==0

2012-11-16T22:33:04+00:00

oom_badness() takes a totalpages argument which says how many pages are
available and it uses it as a base for the score calculation.  The value
is calculated by mem_cgroup_get_limit which considers both limit and
total_swap_pages (resp.  memsw portion of it).

This is usually correct but since fe35004fbf9e ("mm: avoid swapping out
with swappiness==0") we do not swap when swappiness is 0 which means
that we cannot really use up all the totalpages pages.  This in turn
confuses oom score calculation if the memcg limit is much smaller than
the available swap because the used memory (capped by the limit) is
negligible comparing to totalpages so the resulting score is too small
if adj!=0 (typically task with CAP_SYS_ADMIN or non zero oom_score_adj).
A wrong process might be selected as result.

The problem can be worked around by checking mem_cgroup_swappiness==0
and not considering swap at all in such a case.

Signed-off-by: Michal Hocko 
Acked-by: David Rientjes 
Acked-by: Johannes Weiner 
Acked-by: KOSAKI Motohiro 
Acked-by: KAMEZAWA Hiroyuki 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: move mem_cgroup_is_root upwards

2012-10-09T07:22:55+00:00

kmem code uses this function and it is better to not use forward
declarations for static inline functions as some (older) compilers don't
like it:

gcc version 4.3.4 [gcc-4_3-branch revision 152973] (SUSE Linux)

  mm/memcontrol.c:421: warning: `mem_cgroup_is_root' declared inline after being called
  mm/memcontrol.c:421: warning: previous declaration of `mem_cgroup_is_root' was here

Signed-off-by: Michal Hocko 
Cc: Glauber Costa 
Cc: Sachin Kamat 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: cleanup kmem tcp ifdefs

2012-10-09T07:22:54+00:00

TCP kmem accounting is currently guarded by CONFIG_MEMCG_KMEM ifdefs but
the code is not used if !CONFIG_INET so we should rather test for both.
The same applies to net/sock.h, net/ip.h and net/tcp_memcontrol.h but
let's keep those outside of any ifdefs because it is considered safer wrt.
 future maintainability.

Tested with
- CONFIG_INET && CONFIG_MEMCG_KMEM
- !CONFIG_INET && CONFIG_MEMCG_KMEM
- CONFIG_INET && !CONFIG_MEMCG_KMEM
- !CONFIG_INET && !CONFIG_MEMCG_KMEM

Signed-off-by: Sachin Kamat 
Signed-off-by: Michal Hocko 
Cc: Glauber Costa 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

cgroup: mark subsystems with broken hierarchy support and whine if cgroups are nested for them

2012-09-14T19:01:16+00:00

Currently, cgroup hierarchy support is a mess.  cpu related subsystems
behave correctly - configuration, accounting and control on a parent
properly cover its children.  blkio and freezer completely ignore
hierarchy and treat all cgroups as if they're directly under the root
cgroup.  Others show yet different behaviors.

These differing interpretations of cgroup hierarchy make using cgroup
confusing and it impossible to co-mount controllers into the same
hierarchy and obtain sane behavior.

Eventually, we want full hierarchy support from all subsystems and
probably a unified hierarchy.  Users using separate hierarchies
expecting completely different behaviors depending on the mounted
subsystem is deterimental to making any progress on this front.

This patch adds cgroup_subsys.broken_hierarchy and sets it to %true
for controllers which are lacking in hierarchy support.  The goal of
this patch is two-fold.

* Move users away from using hierarchy on currently non-hierarchical
  subsystems, so that implementing proper hierarchy support on those
  doesn't surprise them.

* Keep track of which controllers are broken how and nudge the
  subsystems to implement proper hierarchy support.

For now, start with a single warning message.  We can whine louder
later on.

v2: Fixed a typo spotted by Michal. Warning message updated.

v3: Updated memcg part so that it doesn't generate warning in the
    cases where .use_hierarchy=false doesn't make the behavior
    different from root.use_hierarchy=true.  Fixed a typo spotted by
    Glauber.

v4: Check ->broken_hierarchy after cgroup creation is complete so that
    ->create() can affect the result per Michal.  Dropped unnecessary
    memcg root handling per Michal.

Signed-off-by: Tejun Heo 
Acked-by: Michal Hocko 
Acked-by: Li Zefan 
Acked-by: Serge E. Hallyn 
Cc: Glauber Costa 
Cc: Peter Zijlstra 
Cc: Paul Turner 
Cc: Johannes Weiner 
Cc: Thomas Graf 
Cc: Vivek Goyal 
Cc: Paul Mackerras 
Cc: Ingo Molnar 
Cc: Arnaldo Carvalho de Melo 
Cc: Neil Horman 
Cc: Aneesh Kumar K.V

memcg: add mem_cgroup_from_css() helper

2012-08-01T01:42:49+00:00

Add a mem_cgroup_from_css() helper to replace open-coded invokations of
container_of().  To clarify the code and to add a little more type safety.

[akpm@linux-foundation.org: fix extensive breakage]
Signed-off-by: Wanpeng Li 
Acked-by: Michal Hocko 
Cc: Johannes Weiner 
Cc: KAMEZAWA Hiroyuki 
Cc: Gavin Shan 
Cc: Wanpeng Li 
Cc: Gavin Shan 
Cc: Johannes Weiner 
Cc: KAMEZAWA Hiroyuki 
Cc: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: memcg: only check anon swapin page charges for swap cache

2012-08-01T01:42:49+00:00

shmem knows for sure that the page is in swap cache when attempting to
charge a page, because the cache charge entry function has a check for it.
Only anon pages may be removed from swap cache already when trying to
charge their swapin.

Adjust the comment, though: '4969c11 mm: fix swapin race condition' added
a stable PageSwapCache check under the page lock in the do_swap_page()
before calling the memory controller, so it's unuse_pte()'s pte_same()
that may fail.

Signed-off-by: Johannes Weiner 
Acked-by: KAMEZAWA Hiroyuki 
Acked-by: Michal Hocko 
Cc: David Rientjes 
Cc: Hugh Dickins 
Cc: Johannes Weiner 
Cc: Wanpeng Li 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: memcg: only check swap cache pages for repeated charging

2012-08-01T01:42:49+00:00

Only anon and shmem pages in the swap cache are attempted to be charged
multiple times, from every swap pte fault or from shmem_unuse().  No other
pages require checking PageCgroupUsed().

Charging pages in the swap cache is also serialized by the page lock, and
since both the try_charge and commit_charge are called under the same page
lock section, the PageCgroupUsed() check might as well happen before the
counter charging, let alone reclaim.

Signed-off-by: Johannes Weiner 
Acked-by: KAMEZAWA Hiroyuki 
Acked-by: Michal Hocko 
Cc: David Rientjes 
Cc: Hugh Dickins 
Cc: Johannes Weiner 
Cc: Wanpeng Li 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: memcg: split swapin charge function into private and public part

2012-08-01T01:42:48+00:00

When shmem is charged upon swapin, it does not need to check twice whether
the memory controller is enabled.

Also, shmem pages do not have to be checked for everything that regular
anon pages have to be checked for, so let shmem use the internal version
directly and allow future patches to move around checks that are only
required when swapping in anon pages.

Signed-off-by: Johannes Weiner 
Acked-by: KAMEZAWA Hiroyuki 
Acked-by: Michal Hocko 
Cc: David Rientjes 
Cc: Hugh Dickins 
Cc: Johannes Weiner 
Cc: Wanpeng Li 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: memcg: remove needless !mm fixup to init_mm when charging

2012-08-01T01:42:48+00:00

It does not matter to __mem_cgroup_try_charge() if the passed mm is NULL
or init_mm, it will charge the root memcg in either case.

Also fix up the comment in __mem_cgroup_try_charge() that claimed the
init_mm would be charged when no mm was passed.  It's not really
incorrect, but confusing.  Clarify that the root memcg is charged in this
case.

Signed-off-by: Johannes Weiner 
Acked-by: KAMEZAWA Hiroyuki 
Acked-by: Michal Hocko 
Cc: David Rientjes 
Cc: Hugh Dickins 
Cc: Johannes Weiner 
Cc: Wanpeng Li 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds