• Johannes Weiner's avatar
    mm: oom_kill: simplify OOM killer locking · dc56401f
    Johannes Weiner authored
    The zonelist locking and the oom_sem are two overlapping locks that are
    used to serialize global OOM killing against different things.
    
    The historical zonelist locking serializes OOM kills from allocations with
    overlapping zonelists against each other to prevent killing more tasks
    than necessary in the same memory domain.  Only when neither tasklists nor
    zonelists from two concurrent OOM kills overlap (tasks in separate memcgs
    bound to separate nodes) are OOM kills allowed to execute in parallel.
    
    The younger oom_sem is a read-write lock to serialize OOM killing against
    the PM code trying to disable the OOM killer altogether.
    
    However, the OOM killer is a fairly cold error path, there is really no
    reason to optimize for highly performant and concurrent OOM kills.  And
    the oom_sem is just flat-out redundant.
    
    Replace both locking schemes with a single global mutex serializing OOM
    kills regardless of context.
    Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
    Acked-by: default avatarDavid Rientjes <rientjes@google.com>
    Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Dave Chinner <david@fromorbit.com>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    dc56401f
oom_kill.c 20.6 KB