24 Feb, 2013

1 commit

  • Currently when a memcg oom is happening the oom dump messages is still
    global state and provides few useful info for users. This patch prints
    more pointed memcg page statistics for memcg-oom and take hierarchy into
    consideration:

    Based on Michal's advice, we take hierarchy into consideration: supppose
    we trigger an OOM on A's limit

    root_memcg
    |
    A (use_hierachy=1)
    / \
    B C
    |
    D
    then the printed info will be:

    Memory cgroup stats for /A:...
    Memory cgroup stats for /A/B:...
    Memory cgroup stats for /A/C:...
    Memory cgroup stats for /A/B/D:...

    Following are samples of oom output:

    (1) Before change:

    mal-80 invoked oom-killer:gfp_mask=0xd0, order=0, oom_score_adj=0
    mal-80 cpuset=/ mems_allowed=0
    Pid: 2976, comm: mal-80 Not tainted 3.7.0+ #10
    Call Trace:
    [] dump_header+0x83/0x1ca
    ..... (call trace)
    [] page_fault+0x28/0x30
    <<<<<<<<<<<<<<<<<<<<< memcg specific information
    Task in /A/B/D killed as a result of limit of /A
    memory: usage 101376kB, limit 101376kB, failcnt 57
    memory+swap: usage 101376kB, limit 101376kB, failcnt 0
    kmem: usage 0kB, limit 9007199254740991kB, failcnt 0
    <<<<<<<<<<<<<<<<<<<<< print per cpu pageset stat
    Mem-Info:
    Node 0 DMA per-cpu:
    CPU 0: hi: 0, btch: 1 usd: 0
    ......
    CPU 3: hi: 0, btch: 1 usd: 0
    Node 0 DMA32 per-cpu:
    CPU 0: hi: 186, btch: 31 usd: 173
    ......
    CPU 3: hi: 186, btch: 31 usd: 130
    <<<<<<<<<<<<<<<<<<<<< print global page state
    active_anon:92963 inactive_anon:40777 isolated_anon:0
    active_file:33027 inactive_file:51718 isolated_file:0
    unevictable:0 dirty:3 writeback:0 unstable:0
    free:729995 slab_reclaimable:6897 slab_unreclaimable:6263
    mapped:20278 shmem:35971 pagetables:5885 bounce:0
    free_cma:0
    <<<<<<<<<<<<<<<<<<<<< print per zone page state
    Node 0 DMA free:15836kB ... all_unreclaimable? no
    lowmem_reserve[]: 0 3175 3899 3899
    Node 0 DMA32 free:2888564kB ... all_unrelaimable? no
    lowmem_reserve[]: 0 0 724 724
    lowmem_reserve[]: 0 0 0 0
    Node 0 DMA: 1*4kB (U) ... 3*4096kB (M) = 15836kB
    Node 0 DMA32: 41*4kB (UM) ... 702*4096kB (MR) = 2888316kB
    120710 total pagecache pages
    0 pages in swap cache
    <<<<<<<<<<<<<<<<<<<<< print global swap cache stat
    Swap cache stats: add 0, delete 0, find 0/0
    Free swap = 499708kB
    Total swap = 499708kB
    1040368 pages RAM
    58678 pages reserved
    169065 pages shared
    173632 pages non-shared
    [ pid ] uid tgid total_vm rss nr_ptes swapents oom_score_adj name
    [ 2693] 0 2693 6005 1324 17 0 0 god
    [ 2754] 0 2754 6003 1320 16 0 0 god
    [ 2811] 0 2811 5992 1304 18 0 0 god
    [ 2874] 0 2874 6005 1323 18 0 0 god
    [ 2935] 0 2935 8720 7742 21 0 0 mal-30
    [ 2976] 0 2976 21520 17577 42 0 0 mal-80
    Memory cgroup out of memory: Kill process 2976 (mal-80) score 665 or sacrifice child
    Killed process 2976 (mal-80) total-vm:86080kB, anon-rss:69964kB, file-rss:344kB

    We can see that messages dumped by show_free_areas() are longsome and can
    provide so limited info for memcg that just happen oom.

    (2) After change
    mal-80 invoked oom-killer: gfp_mask=0xd0, order=0, oom_score_adj=0
    mal-80 cpuset=/ mems_allowed=0
    Pid: 2704, comm: mal-80 Not tainted 3.7.0+ #10
    Call Trace:
    [] dump_header+0x83/0x1d1
    .......(call trace)
    [] page_fault+0x28/0x30
    Task in /A/B/D killed as a result of limit of /A
    <<<<<<<<<<<<<<<<<<<<< memcg specific information
    memory: usage 102400kB, limit 102400kB, failcnt 140
    memory+swap: usage 102400kB, limit 102400kB, failcnt 0
    kmem: usage 0kB, limit 9007199254740991kB, failcnt 0
    Memory cgroup stats for /A: cache:32KB rss:30984KB mapped_file:0KB swap:0KB inactive_anon:6912KB active_anon:24072KB inactive_file:32KB active_file:0KB unevictable:0KB
    Memory cgroup stats for /A/B: cache:0KB rss:0KB mapped_file:0KB swap:0KB inactive_anon:0KB active_anon:0KB inactive_file:0KB active_file:0KB unevictable:0KB
    Memory cgroup stats for /A/C: cache:0KB rss:0KB mapped_file:0KB swap:0KB inactive_anon:0KB active_anon:0KB inactive_file:0KB active_file:0KB unevictable:0KB
    Memory cgroup stats for /A/B/D: cache:32KB rss:71352KB mapped_file:0KB swap:0KB inactive_anon:6656KB active_anon:64696KB inactive_file:16KB active_file:16KB unevictable:0KB
    [ pid ] uid tgid total_vm rss nr_ptes swapents oom_score_adj name
    [ 2260] 0 2260 6006 1325 18 0 0 god
    [ 2383] 0 2383 6003 1319 17 0 0 god
    [ 2503] 0 2503 6004 1321 18 0 0 god
    [ 2622] 0 2622 6004 1321 16 0 0 god
    [ 2695] 0 2695 8720 7741 22 0 0 mal-30
    [ 2704] 0 2704 21520 17839 43 0 0 mal-80
    Memory cgroup out of memory: Kill process 2704 (mal-80) score 669 or sacrifice child
    Killed process 2704 (mal-80) total-vm:86080kB, anon-rss:71016kB, file-rss:340kB

    This version provides more pointed info for memcg in "Memory cgroup stats
    for XXX" section.

    Signed-off-by: Sha Zhengju
    Acked-by: Michal Hocko
    Cc: KAMEZAWA Hiroyuki
    Acked-by: David Rientjes
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Sha Zhengju
     

13 Dec, 2012

3 commits

  • out_of_memory() will already cause current to schedule if it has not been
    killed, so doing it again in pagefault_out_of_memory() is redundant.
    Remove it.

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

    David Rientjes
     
  • To lock the entire system from parallel oom killing, it's possible to pass
    in a zonelist with all zones rather than using for_each_populated_zone()
    for the iteration. This obsoletes try_set_system_oom() and
    clear_system_oom() so that they can be removed.

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

    David Rientjes
     
  • N_HIGH_MEMORY stands for the nodes that has normal or high memory.
    N_MEMORY stands for the nodes that has any memory.

    The code here need to handle with the nodes which have memory, we should
    use N_MEMORY instead.

    Signed-off-by: Lai Jiangshan
    Acked-by: Hillf Danton
    Signed-off-by: Wen Congyang
    Cc: Christoph Lameter
    Cc: Lin Feng
    Cc: David Rientjes
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Lai Jiangshan
     

12 Dec, 2012

3 commits

  • test_set_oom_score_adj() and compare_swap_oom_score_adj() are used to
    specify that current should be killed first if an oom condition occurs in
    between the two calls.

    The usage is

    short oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX);
    ...
    compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, oom_score_adj);

    to store the thread's oom_score_adj, temporarily change it to the maximum
    score possible, and then restore the old value if it is still the same.

    This happens to still be racy, however, if the user writes
    OOM_SCORE_ADJ_MAX to /proc/pid/oom_score_adj in between the two calls.
    The compare_swap_oom_score_adj() will then incorrectly reset the old value
    prior to the write of OOM_SCORE_ADJ_MAX.

    To fix this, introduce a new oom_flags_t member in struct signal_struct
    that will be used for per-thread oom killer flags. KSM and swapoff can
    now use a bit in this member to specify that threads should be killed
    first in oom conditions without playing around with oom_score_adj.

    This also allows the correct oom_score_adj to always be shown when reading
    /proc/pid/oom_score.

    Signed-off-by: David Rientjes
    Cc: KAMEZAWA Hiroyuki
    Cc: KOSAKI Motohiro
    Reviewed-by: Michal Hocko
    Cc: Anton Vorontsov
    Cc: Oleg Nesterov
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     
  • The maximum oom_score_adj is 1000 and the minimum oom_score_adj is -1000,
    so this range can be represented by the signed short type with no
    functional change. The extra space this frees up in struct signal_struct
    will be used for per-thread oom kill flags in the next patch.

    Signed-off-by: David Rientjes
    Cc: KAMEZAWA Hiroyuki
    Cc: KOSAKI Motohiro
    Reviewed-by: Michal Hocko
    Cc: Anton Vorontsov
    Cc: Oleg Nesterov
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     
  • Exiting threads, those with PF_EXITING set, can pagefault and require
    memory before they can make forward progress. This happens, for instance,
    when a process must fault task->robust_list, a userspace structure, before
    detaching its memory.

    These threads also aren't guaranteed to get access to memory reserves
    unless oom killed or killed from userspace. The oom killer won't grant
    memory reserves if other threads are also exiting other than current and
    stalling at the same point. This prevents needlessly killing processes
    when others are already exiting.

    Instead of special casing all the possible situations between PF_EXITING
    getting set and a thread detaching its mm where it may allocate memory,
    which probably wouldn't get updated when a change is made to the exit
    path, the solution is to give all exiting threads access to memory
    reserves if they call the oom killer. This allows them to quickly
    allocate, detach its mm, and free the memory it represents.

    Summary of Luigi's bug report:

    : He had an oom condition where threads were faulting on task->robust_list
    : and repeatedly called the oom killer but it would defer killing a thread
    : because it saw other PF_EXITING threads. This can happen anytime we need
    : to allocate memory after setting PF_EXITING and before detaching our mm;
    : if there are other threads in the same state then the oom killer won't do
    : anything unless one of them happens to be killed from userspace.
    :
    : So instead of only deferring for PF_EXITING and !task->robust_list, it's
    : better to just give them access to memory reserves to prevent a potential
    : livelock so that any other faults that may be introduced in the future in
    : the exit path don't cause the same problem (and hopefully we don't allow
    : too many of those!).

    Signed-off-by: David Rientjes
    Acked-by: Minchan Kim
    Tested-by: Luigi Semenzato
    Cc: KOSAKI Motohiro
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     

09 Oct, 2012

1 commit


01 Aug, 2012

8 commits

  • By globally defining check_panic_on_oom(), the memcg oom handler can be
    moved entirely to mm/memcontrol.c. This removes the ugly #ifdef in the
    oom killer and cleans up the code.

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

    David Rientjes
     
  • Since exiting tasks require write_lock_irq(&tasklist_lock) several times,
    try to reduce the amount of time the readside is held for oom kills. This
    makes the interface with the memcg oom handler more consistent since it
    now never needs to take tasklist_lock unnecessarily.

    The only time the oom killer now takes tasklist_lock is when iterating the
    children of the selected task, everything else is protected by
    rcu_read_lock().

    This requires that a reference to the selected process, p, is grabbed
    before calling oom_kill_process(). It may release it and grab a reference
    on another one of p's threads if !p->mm, but it also guarantees that it
    will release the reference before returning.

    [hughd@google.com: fix duplicate put_task_struct()]
    Signed-off-by: David Rientjes
    Cc: KAMEZAWA Hiroyuki
    Reviewed-by: Michal Hocko
    Cc: Oleg Nesterov
    Cc: KOSAKI Motohiro
    Cc: Johannes Weiner
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     
  • The global oom killer is serialized by the per-zonelist
    try_set_zonelist_oom() which is used in the page allocator. Concurrent
    oom kills are thus a rare event and only occur in systems using
    mempolicies and with a large number of nodes.

    Memory controller oom kills, however, can frequently be concurrent since
    there is no serialization once the oom killer is called for oom conditions
    in several different memcgs in parallel.

    This creates a massive contention on tasklist_lock since the oom killer
    requires the readside for the tasklist iteration. If several memcgs are
    calling the oom killer, this lock can be held for a substantial amount of
    time, especially if threads continue to enter it as other threads are
    exiting.

    Since the exit path grabs the writeside of the lock with irqs disabled in
    a few different places, this can cause a soft lockup on cpus as a result
    of tasklist_lock starvation.

    The kernel lacks unfair writelocks, and successful calls to the oom killer
    usually result in at least one thread entering the exit path, so an
    alternative solution is needed.

    This patch introduces a seperate oom handler for memcgs so that they do
    not require tasklist_lock for as much time. Instead, it iterates only
    over the threads attached to the oom memcg and grabs a reference to the
    selected thread before calling oom_kill_process() to ensure it doesn't
    prematurely exit.

    This still requires tasklist_lock for the tasklist dump, iterating
    children of the selected process, and killing all other threads on the
    system sharing the same memory as the selected victim. So while this
    isn't a complete solution to tasklist_lock starvation, it significantly
    reduces the amount of time that it is held.

    Acked-by: KAMEZAWA Hiroyuki
    Acked-by: Michal Hocko
    Signed-off-by: David Rientjes
    Cc: Oleg Nesterov
    Cc: KOSAKI Motohiro
    Reviewed-by: Sha Zhengju
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     
  • This patch introduces a helper function to process each thread during the
    iteration over the tasklist. A new return type, enum oom_scan_t, is
    defined to determine the future behavior of the iteration:

    - OOM_SCAN_OK: continue scanning the thread and find its badness,

    - OOM_SCAN_CONTINUE: do not consider this thread for oom kill, it's
    ineligible,

    - OOM_SCAN_ABORT: abort the iteration and return, or

    - OOM_SCAN_SELECT: always select this thread with the highest badness
    possible.

    There is no functional change with this patch. This new helper function
    will be used in the next patch in the memory controller.

    Reviewed-by: KAMEZAWA Hiroyuki
    Acked-by: KOSAKI Motohiro
    Reviewed-by: Michal Hocko
    Signed-off-by: David Rientjes
    Cc: Oleg Nesterov
    Reviewed-by: Sha Zhengju
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     
  • Sanity:

    CONFIG_CGROUP_MEM_RES_CTLR -> CONFIG_MEMCG
    CONFIG_CGROUP_MEM_RES_CTLR_SWAP -> CONFIG_MEMCG_SWAP
    CONFIG_CGROUP_MEM_RES_CTLR_SWAP_ENABLED -> CONFIG_MEMCG_SWAP_ENABLED
    CONFIG_CGROUP_MEM_RES_CTLR_KMEM -> CONFIG_MEMCG_KMEM

    [mhocko@suse.cz: fix missed bits]
    Cc: Glauber Costa
    Acked-by: Michal Hocko
    Cc: Johannes Weiner
    Cc: KAMEZAWA Hiroyuki
    Cc: Hugh Dickins
    Cc: Tejun Heo
    Cc: Aneesh Kumar K.V
    Cc: David Rientjes
    Cc: KOSAKI Motohiro
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Andrew Morton
     
  • The number of ptes and swap entries are used in the oom killer's badness
    heuristic, so they should be shown in the tasklist dump.

    This patch adds those fields and replaces cpu and oom_adj values that are
    currently emitted. Cpu isn't interesting and oom_adj is deprecated and
    will be removed later this year, the same information is already displayed
    as oom_score_adj which is used internally.

    At the same time, make the documentation a little more clear to state this
    information is helpful to determine why the oom killer chose the task it
    did to kill.

    Signed-off-by: David Rientjes
    Cc: KAMEZAWA Hiroyuki
    Cc: KOSAKI Motohiro
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     
  • /proc/sys/vm/oom_kill_allocating_task will immediately kill current when
    the oom killer is called to avoid a potentially expensive tasklist scan
    for large systems.

    Currently, however, it is not checking current's oom_score_adj value which
    may be OOM_SCORE_ADJ_MIN, meaning that it has been disabled from oom
    killing.

    This patch avoids killing current in such a condition and simply falls
    back to the tasklist scan since memory still needs to be freed.

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

    David Rientjes
     
  • The oom killer currently schedules away from current in an uninterruptible
    sleep if it does not have access to memory reserves. It's possible that
    current was killed because it shares memory with the oom killed thread or
    because it was killed by the user in the interim, however.

    This patch only schedules away from current if it does not have a pending
    kill, i.e. if it does not share memory with the oom killed thread. It's
    possible that it will immediately retry its memory allocation and fail,
    but it will immediately be given access to memory reserves if it calls the
    oom killer again.

    This prevents the delay of memory freeing when threads that share memory
    with the oom killed thread get unnecessarily scheduled.

    Signed-off-by: David Rientjes
    Cc: Oleg Nesterov
    Acked-by: KOSAKI Motohiro
    Acked-by: KAMEZAWA Hiroyuki
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     

21 Jun, 2012

2 commits

  • Fix kernel-doc warnings such as

    Warning(../mm/page_cgroup.c:432): No description found for parameter 'id'
    Warning(../mm/page_cgroup.c:432): Excess function parameter 'mem' description in 'swap_cgroup_record'

    Signed-off-by: Wanpeng Li
    Cc: Randy Dunlap
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Wanpeng Li
     
  • The divide in p->signal->oom_score_adj * totalpages / 1000 within
    oom_badness() was causing an overflow of the signed long data type.

    This adds both the root bias and p->signal->oom_score_adj before doing the
    normalization which fixes the issue and also cleans up the calculation.

    Tested-by: Dave Jones
    Signed-off-by: David Rientjes
    Cc: KOSAKI Motohiro
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     

09 Jun, 2012

1 commit

  • If the privileges given to root threads (3% of allowable memory) or a
    negative value of /proc/pid/oom_score_adj happen to exceed the amount of
    rss of a thread, its badness score overflows as a result of commit
    a7f638f999ff ("mm, oom: normalize oom scores to oom_score_adj scale only
    for userspace").

    Fix this by making the type signed and return 1, meaning the thread is
    still eligible for kill, if the value is negative.

    Reported-by: Dave Jones
    Acked-by: Oleg Nesterov
    Signed-off-by: David Rientjes
    Signed-off-by: Linus Torvalds

    David Rientjes
     

30 May, 2012

1 commit

  • The oom_score_adj scale ranges from -1000 to 1000 and represents the
    proportion of memory available to the process at allocation time. This
    means an oom_score_adj value of 300, for example, will bias a process as
    though it was using an extra 30.0% of available memory and a value of
    -350 will discount 35.0% of available memory from its usage.

    The oom killer badness heuristic also uses this scale to report the oom
    score for each eligible process in determining the "best" process to
    kill. Thus, it can only differentiate each process's memory usage by
    0.1% of system RAM.

    On large systems, this can end up being a large amount of memory: 256MB
    on 256GB systems, for example.

    This can be fixed by having the badness heuristic to use the actual
    memory usage in scoring threads and then normalizing it to the
    oom_score_adj scale for userspace. This results in better comparison
    between eligible threads for kill and no change from the userspace
    perspective.

    Suggested-by: KOSAKI Motohiro
    Tested-by: Dave Jones
    Signed-off-by: David Rientjes
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     

03 May, 2012

1 commit


24 Mar, 2012

1 commit

  • Change oom_kill_task() to use do_send_sig_info(SEND_SIG_FORCED) instead
    of force_sig(SIGKILL). With the recent changes we do not need force_ to
    kill the CLONE_NEWPID tasks.

    And this is more correct. force_sig() can race with the exiting thread
    even if oom_kill_task() checks p->mm != NULL, while
    do_send_sig_info(group => true) kille the whole process.

    Signed-off-by: Oleg Nesterov
    Cc: Tejun Heo
    Cc: Anton Vorontsov
    Cc: "Eric W. Biederman"
    Cc: KOSAKI Motohiro
    Cc: David Rientjes
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Oleg Nesterov
     

22 Mar, 2012

6 commits

  • The oom killer typically displays the allocation order at the time of oom
    as a part of its diangostic messages (for global, cpuset, and mempolicy
    ooms).

    The memory controller may also pass the charge order to the oom killer so
    it can emit the same information. This is useful in determining how large
    the memory allocation is that triggered the oom killer.

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

    David Rientjes
     
  • The oom killer chooses not to kill a thread if:

    - an eligible thread has already been oom killed and has yet to exit,
    and

    - an eligible thread is exiting but has yet to free all its memory and
    is not the thread attempting to currently allocate memory.

    SysRq+F manually invokes the global oom killer to kill a memory-hogging
    task. This is normally done as a last resort to free memory when no
    progress is being made or to test the oom killer itself.

    For both uses, we always want to kill a thread and never defer. This
    patch causes SysRq+F to always kill an eligible thread and can be used to
    force a kill even if another oom killed thread has failed to exit.

    Signed-off-by: David Rientjes
    Acked-by: KOSAKI Motohiro
    Acked-by: Pekka Enberg
    Acked-by: KAMEZAWA Hiroyuki
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     
  • printk_ratelimit() uses the global ratelimit state for all printks. The
    oom killer should not be subjected to this state just because another
    subsystem or driver may be flooding the kernel log.

    This patch introduces printk ratelimiting specifically for the oom killer.

    Signed-off-by: David Rientjes
    Acked-by: KOSAKI Motohiro
    Reviewed-by: KAMEZAWA Hiroyuki
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     
  • If a thread is chosen for oom kill and is already PF_EXITING, then the oom
    killer simply sets TIF_MEMDIE and returns. This allows the thread to have
    access to memory reserves so that it may quickly exit. This logic is
    preceeded with a comment saying there's no need to alarm the sysadmin.
    This patch adds truth to that statement.

    There's no need to emit any warning about the oom condition if the thread
    is already exiting since it will not be killed. In this condition, just
    silently return the oom killer since its only giving access to memory
    reserves and is otherwise a no-op.

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

    David Rientjes
     
  • oom_kill_task() has a single caller, so fold it into its parent function,
    oom_kill_process(). Slightly reduces the number of lines in the oom
    killer.

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

    David Rientjes
     
  • oom_kill_task() returns non-zero iff the chosen process does not have any
    threads with an attached ->mm.

    In such a case, it's better to just return to the page allocator and retry
    the allocation because memory could have been freed in the interim and the
    oom condition may no longer exist. It's unnecessary to loop in the oom
    killer and find another thread to kill.

    This allows both oom_kill_task() and oom_kill_process() to be converted to
    void functions. If the oom condition persists, the oom killer will be
    recalled.

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

    David Rientjes
     

13 Jan, 2012

2 commits


11 Jan, 2012

1 commit

  • oom_score_adj is used for guarding processes from OOM-Killer. One of
    problem is that it's inherited at fork(). When a daemon set oom_score_adj
    and make children, it's hard to know where the value is set.

    This patch adds some tracepoints useful for debugging. This patch adds
    3 trace points.
    - creating new task
    - renaming a task (exec)
    - set oom_score_adj

    To debug, users need to enable some trace pointer. Maybe filtering is useful as

    # EVENT=/sys/kernel/debug/tracing/events/task/
    # echo "oom_score_adj != 0" > $EVENT/task_newtask/filter
    # echo "oom_score_adj != 0" > $EVENT/task_rename/filter
    # echo 1 > $EVENT/enable
    # EVENT=/sys/kernel/debug/tracing/events/oom/
    # echo 1 > $EVENT/enable

    output will be like this.
    # grep oom /sys/kernel/debug/tracing/trace
    bash-7699 [007] d..3 5140.744510: oom_score_adj_update: pid=7699 comm=bash oom_score_adj=-1000
    bash-7699 [007] ...1 5151.818022: task_newtask: pid=7729 comm=bash clone_flags=1200011 oom_score_adj=-1000
    ls-7729 [003] ...2 5151.818504: task_rename: pid=7729 oldcomm=bash newcomm=ls oom_score_adj=-1000
    bash-7699 [002] ...1 5175.701468: task_newtask: pid=7730 comm=bash clone_flags=1200011 oom_score_adj=-1000
    grep-7730 [007] ...2 5175.701993: task_rename: pid=7730 oldcomm=bash newcomm=grep oom_score_adj=-1000

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

    KAMEZAWA Hiroyuki
     

22 Dec, 2011

1 commit

  • * master: (848 commits)
    SELinux: Fix RCU deref check warning in sel_netport_insert()
    binary_sysctl(): fix memory leak
    mm/vmalloc.c: remove static declaration of va from __get_vm_area_node
    ipmi_watchdog: restore settings when BMC reset
    oom: fix integer overflow of points in oom_badness
    memcg: keep root group unchanged if creation fails
    nilfs2: potential integer overflow in nilfs_ioctl_clean_segments()
    nilfs2: unbreak compat ioctl
    cpusets: stall when updating mems_allowed for mempolicy or disjoint nodemask
    evm: prevent racing during tfm allocation
    evm: key must be set once during initialization
    mmc: vub300: fix type of firmware_rom_wait_states module parameter
    Revert "mmc: enable runtime PM by default"
    mmc: sdhci: remove "state" argument from sdhci_suspend_host
    x86, dumpstack: Fix code bytes breakage due to missing KERN_CONT
    IB/qib: Correct sense on freectxts increment and decrement
    RDMA/cma: Verify private data length
    cgroups: fix a css_set not found bug in cgroup_attach_proc
    oprofile: Fix uninitialized memory access when writing to writing to oprofilefs
    Revert "xen/pv-on-hvm kexec: add xs_reset_watches to shutdown watches from old kernel"
    ...

    Conflicts:
    kernel/cgroup_freezer.c

    Rafael J. Wysocki
     

21 Dec, 2011

1 commit

  • An integer overflow will happen on 64bit archs if task's sum of rss,
    swapents and nr_ptes exceeds (2^31)/1000 value. This was introduced by
    commit

    f755a04 oom: use pte pages in OOM score

    where the oom score computation was divided into several steps and it's no
    longer computed as one expression in unsigned long(rss, swapents, nr_pte
    are unsigned long), where the result value assigned to points(int) is in
    range(1..1000). So there could be an int overflow while computing

    176 points *= 1000;

    and points may have negative value. Meaning the oom score for a mem hog task
    will be one.

    196 if (points
    Acked-by: KOSAKI Motohiro
    Acked-by: Oleg Nesterov
    Acked-by: David Rientjes
    Cc: [2.6.36+]
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Frantisek Hrbata
     

22 Nov, 2011

1 commit

  • thaw_process() now has only internal users - system and cgroup
    freezers. Remove the unnecessary return value, rename, unexport and
    collapse __thaw_process() into it. This will help further updates to
    the freezer code.

    -v3: oom_kill grew a use of thaw_process() while this patch was
    pending. Convert it to use __thaw_task() for now. In the longer
    term, this should be handled by allowing tasks to die if killed
    even if it's frozen.

    -v2: minor style update as suggested by Matt.

    Signed-off-by: Tejun Heo
    Cc: Paul Menage
    Cc: Matt Helsley

    Tejun Heo
     

16 Nov, 2011

1 commit

  • Commit c9f01245 ("oom: remove oom_disable_count") has removed the
    oom_disable_count counter which has been used for early break out from
    oom_badness so we could never select a task with oom_score_adj set to
    OOM_SCORE_ADJ_MIN (oom disabled).

    Now that the counter is gone we are always going through heuristics
    calculation and we always return a non zero positive value. This means
    that we can end up killing a task with OOM disabled because it is
    indistinguishable from regular tasks with 1% resp. CAP_SYS_ADMIN tasks
    with 3% usage of memory or tasks with oom_score_adj set but OOM enabled.

    Let's break out early if the task should have OOM disabled.

    Signed-off-by: Michal Hocko
    Acked-by: David Rientjes
    Acked-by: KOSAKI Motohiro
    Cc: Oleg Nesterov
    Cc: Ying Han
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Michal Hocko
     

07 Nov, 2011

1 commit

  • * 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux: (230 commits)
    Revert "tracing: Include module.h in define_trace.h"
    irq: don't put module.h into irq.h for tracking irqgen modules.
    bluetooth: macroize two small inlines to avoid module.h
    ip_vs.h: fix implicit use of module_get/module_put from module.h
    nf_conntrack.h: fix up fallout from implicit moduleparam.h presence
    include: replace linux/module.h with "struct module" wherever possible
    include: convert various register fcns to macros to avoid include chaining
    crypto.h: remove unused crypto_tfm_alg_modname() inline
    uwb.h: fix implicit use of asm/page.h for PAGE_SIZE
    pm_runtime.h: explicitly requires notifier.h
    linux/dmaengine.h: fix implicit use of bitmap.h and asm/page.h
    miscdevice.h: fix up implicit use of lists and types
    stop_machine.h: fix implicit use of smp.h for smp_processor_id
    of: fix implicit use of errno.h in include/linux/of.h
    of_platform.h: delete needless include
    acpi: remove module.h include from platform/aclinux.h
    miscdevice.h: delete unnecessary inclusion of module.h
    device_cgroup.h: delete needless include
    net: sch_generic remove redundant use of
    net: inet_timewait_sock doesnt need
    ...

    Fix up trivial conflicts (other header files, and removal of the ab3550 mfd driver) in
    - drivers/media/dvb/frontends/dibx000_common.c
    - drivers/media/video/{mt9m111.c,ov6650.c}
    - drivers/mfd/ab3550-core.c
    - include/linux/dmaengine.h

    Linus Torvalds
     

01 Nov, 2011

4 commits

  • test_set_oom_score_adj() was introduced in 72788c385604 ("oom: replace
    PF_OOM_ORIGIN with toggling oom_score_adj") to temporarily elevate
    current's oom_score_adj for ksm and swapoff without requiring an
    additional per-process flag.

    Using that function to both set oom_score_adj to OOM_SCORE_ADJ_MAX and
    then reinstate the previous value is racy since it's possible that
    userspace can set the value to something else itself before the old value
    is reinstated. That results in userspace setting current's oom_score_adj
    to a different value and then the kernel immediately setting it back to
    its previous value without notification.

    To fix this, a new compare_swap_oom_score_adj() function is introduced
    with the same semantics as the compare and swap CAS instruction, or
    CMPXCHG on x86. It is used to reinstate the previous value of
    oom_score_adj if and only if the present value is the same as the old
    value.

    Signed-off-by: David Rientjes
    Cc: Oleg Nesterov
    Cc: Ying Han
    Cc: KOSAKI Motohiro
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     
  • This removes mm->oom_disable_count entirely since it's unnecessary and
    currently buggy. The counter was intended to be per-process but it's
    currently decremented in the exit path for each thread that exits, causing
    it to underflow.

    The count was originally intended to prevent oom killing threads that
    share memory with threads that cannot be killed since it doesn't lead to
    future memory freeing. The counter could be fixed to represent all
    threads sharing the same mm, but it's better to remove the count since:

    - it is possible that the OOM_DISABLE thread sharing memory with the
    victim is waiting on that thread to exit and will actually cause
    future memory freeing, and

    - there is no guarantee that a thread is disabled from oom killing just
    because another thread sharing its mm is oom disabled.

    Signed-off-by: David Rientjes
    Reported-by: Oleg Nesterov
    Reviewed-by: Oleg Nesterov
    Cc: Ying Han
    Cc: KOSAKI Motohiro
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     
  • After selecting a task to kill, the oom killer iterates all processes and
    kills all other threads that share the same mm_struct in different thread
    groups. It would not otherwise be helpful to kill a thread if its memory
    would not be subsequently freed.

    A kernel thread, however, may assume a user thread's mm by using
    use_mm(). This is only temporary and should not result in sending a
    SIGKILL to that kthread.

    This patch ensures that only user threads and not kthreads are sent a
    SIGKILL if they share the same mm_struct as the oom killed task.

    Signed-off-by: David Rientjes
    Reviewed-by: Michal Hocko
    Reviewed-by: KOSAKI Motohiro
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes
     
  • If a thread has been oom killed and is frozen, thaw it before returning to
    the page allocator. Otherwise, it can stay frozen indefinitely and no
    memory will be freed.

    Signed-off-by: David Rientjes
    Reported-by: Konstantin Khlebnikov
    Cc: Oleg Nesterov
    Cc: KOSAKI Motohiro
    Cc: KAMEZAWA Hiroyuki
    Cc: "Rafael J. Wysocki"
    Acked-by: Michal Hocko
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    David Rientjes