• KOSAKI Motohiro's avatar
    oom: move oom_adj value from task_struct to signal_struct · 28b83c51
    KOSAKI Motohiro authored
    Currently, OOM logic callflow is here.
    
        __out_of_memory()
            select_bad_process()            for each task
                badness()                   calculate badness of one task
                    oom_kill_process()      search child
                        oom_kill_task()     kill target task and mm shared tasks with it
    
    example, process-A have two thread, thread-A and thread-B and it have very
    fat memory and each thread have following oom_adj and oom_score.
    
         thread-A: oom_adj = OOM_DISABLE, oom_score = 0
         thread-B: oom_adj = 0,           oom_score = very-high
    
    Then, select_bad_process() select thread-B, but oom_kill_task() refuse
    kill the task because thread-A have OOM_DISABLE.  Thus __out_of_memory()
    call select_bad_process() again.  but select_bad_process() select the same
    task.  It mean kernel fall in livelock.
    
    The fact is, select_bad_process() must select killable task.  otherwise
    OOM logic go into livelock.
    
    And root cause is, oom_adj shouldn't be per-thread value.  it should be
    per-process value because OOM-killer kill a process, not thread.  Thus
    This patch moves oomkilladj (now more appropriately named oom_adj) from
    struct task_struct to struct signal_struct.  it naturally prevent
    select_bad_process() choose wrong task.
    Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Cc: Paul Menage <menage@google.com>
    Cc: David Rientjes <rientjes@google.com>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    28b83c51
sched.h 73.7 KB