From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Subject: mm,oom_reaper: do not attempt to reap a task twice "mm, oom_reaper: do not attempt to reap a task twice" tried to give the OOM reaper one more chance to retry using MMF_OOM_NOT_REAPABLE flag. But the usefulness of the flag is rather limited and actually never shown in practice. If the flag is set, it means that the holder of mm->mmap_sem cannot call up_write() due to presumably being blocked at unkillable wait waiting for other thread's memory allocation. But since one of threads sharing that mm will queue that mm immediately via task_will_free_mem() shortcut (otherwise, oom_badness() will select the same mm again due to oom_score_adj value unchanged), retrying MMF_OOM_NOT_REAPABLE mm is unlikely helpful. Let's always set MMF_OOM_REAPED. Link: http://lkml.kernel.org/r/1472119394-11342-3-git-send-email-mhocko@xxxxxxxxxx Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/sched.h | 1 - mm/oom_kill.c | 15 +++------------ 2 files changed, 3 insertions(+), 13 deletions(-) diff -puN include/linux/sched.h~mmoom_reaper-do-not-attempt-to-reap-a-task-twice include/linux/sched.h --- a/include/linux/sched.h~mmoom_reaper-do-not-attempt-to-reap-a-task-twice +++ a/include/linux/sched.h @@ -525,7 +525,6 @@ static inline int get_dumpable(struct mm #define MMF_HAS_UPROBES 19 /* has uprobes */ #define MMF_RECALC_UPROBES 20 /* MMF_HAS_UPROBES can be wrong */ #define MMF_OOM_REAPED 21 /* mm has been already reaped */ -#define MMF_OOM_NOT_REAPABLE 22 /* mm couldn't be reaped */ #define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK) diff -puN mm/oom_kill.c~mmoom_reaper-do-not-attempt-to-reap-a-task-twice mm/oom_kill.c --- a/mm/oom_kill.c~mmoom_reaper-do-not-attempt-to-reap-a-task-twice +++ a/mm/oom_kill.c @@ -578,20 +578,11 @@ static void oom_reap_task(struct task_st if (attempts <= MAX_OOM_REAP_RETRIES) goto done; + /* Ignore this mm because somebody can't call up_write(mmap_sem). */ + set_bit(MMF_OOM_REAPED, &mm->flags); + pr_info("oom_reaper: unable to reap pid:%d (%s)\n", task_pid_nr(tsk), tsk->comm); - - /* - * If we've already tried to reap this task in the past and - * failed it probably doesn't make much sense to try yet again - * so hide the mm from the oom killer so that it can move on - * to another task with a different mm struct. - */ - if (test_and_set_bit(MMF_OOM_NOT_REAPABLE, &mm->flags)) { - pr_info("oom_reaper: giving up pid:%d (%s)\n", - task_pid_nr(tsk), tsk->comm); - set_bit(MMF_OOM_REAPED, &mm->flags); - } debug_show_all_locks(); done: _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
