• Ying Han's avatar
    oom: add per-mm oom disable count · 3d5992d2
    Ying Han authored
    It's pointless to kill a task if another thread sharing its mm cannot be
    killed to allow future memory freeing.  A subsequent patch will prevent
    kills in such cases, but first it's necessary to have a way to flag a task
    that shares memory with an OOM_DISABLE task that doesn't incur an
    additional tasklist scan, which would make select_bad_process() an O(n^2)
    function.
    
    This patch adds an atomic counter to struct mm_struct that follows how
    many threads attached to it have an oom_score_adj of OOM_SCORE_ADJ_MIN.
    They cannot be killed by the kernel, so their memory cannot be freed in
    oom conditions.
    
    This only requires task_lock() on the task that we're operating on, it
    does not require mm->mmap_sem since task_lock() pins the mm and the
    operation is atomic.
    
    [rientjes@google.com: changelog and sys_unshare() code]
    [rientjes@google.com: protect oom_disable_count with task_lock in fork]
    [rientjes@google.com: use old_mm for oom_disable_count in exec]
    Signed-off-by: default avatarYing Han <yinghan@google.com>
    Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Cc: Rik van Riel <riel@redhat.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    3d5992d2
fork.c 42.1 KB