On Tue, 11 Jul 2017, Michal Hocko wrote:
> This?
> ---
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 5dc0ff22d567..e155d1d8064f 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -470,11 +470,14 @@ static bool __oom_reap_task_mm(struct task_struct *tsk,
> struct mm_struct *mm)
> {
> struct mmu_gather tlb;
> struct vm_area_struct *vma;
> - bool ret = true;
>
> if (!down_read_trylock(&mm->mmap_sem))
> return false;
>
> + /* There is nothing to reap so bail out without signs in the log */
> + if (!mm->mmap)
> + goto unlock;
> +
> /*
> * Tell all users of get_user/copy_from_user etc... that the content
> * is no longer stable. No barriers really needed because unmapping
> @@ -508,9 +511,10 @@ static bool __oom_reap_task_mm(struct task_struct *tsk,
> struct mm_struct *mm)
> K(get_mm_counter(mm, MM_ANONPAGES)),
> K(get_mm_counter(mm, MM_FILEPAGES)),
> K(get_mm_counter(mm, MM_SHMEMPAGES)));
> +unlock:
> up_read(&mm->mmap_sem);
>
> - return ret;
> + return true;
> }
>
> #define MAX_OOM_REAP_RETRIES 10
Yes, this folded in with the original RFC patch appears to work better
with light testing.
However, I think MAX_OOM_REAP_RETRIES and/or the timeout of HZ/10 needs to
be increased as well to address the issue that Tetsuo pointed out. The
oom reaper shouldn't be required to do any work unless it is resolving a
livelock, and that scenario should be relatively rare. The oom killer
being a natural ultra slow path, I think it would be justifiable to wait
longer or retry more times than simply 1 second before declaring that
reaping is not possible. It reduces the likelihood of additional oom
killing.
