On Wed 23-05-18 19:24:48, Tetsuo Handa wrote:
> Michal Hocko wrote:
> > > I don't understand why you are talking about PF_WQ_WORKER case.
> >
> > Because that seems to be the reason to have it there as per your
> > comment.
>
> OK. Then, I will fold below change into my patch.
>
> if (did_some_progress) {
> no_progress_loops = 0;
> + /*
> -+ * This schedule_timeout_*() serves as a guaranteed sleep for
> -+ * PF_WQ_WORKER threads when __zone_watermark_ok() == false.
> ++ * Try to give the OOM killer/reaper/victims some time for
> ++ * releasing memory.
> + */
> + if (!tsk_is_oom_victim(current))
> + schedule_timeout_uninterruptible(1);
>
> But Roman, my patch conflicts with your "mm, oom: cgroup-aware OOM killer" patch
> in linux-next. And it seems to me that your patch contains a bug which leads to
> premature memory allocation failure explained below.
>
> @@ -1029,6 +1050,7 @@ bool out_of_memory(struct oom_control *oc)
> {
> unsigned long freed = 0;
> enum oom_constraint constraint = CONSTRAINT_NONE;
> + bool delay = false; /* if set, delay next allocation attempt */
>
> if (oom_killer_disabled)
> return false;
> @@ -1073,27 +1095,39 @@ bool out_of_memory(struct oom_control *oc)
> current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) &&
> current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
> get_task_struct(current);
> - oc->chosen = current;
> + oc->chosen_task = current;
> oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
> return true;
> }
>
> + if (mem_cgroup_select_oom_victim(oc)) {
>
> /* mem_cgroup_select_oom_victim() returns true if select_victim_memcg() made
> oc->chosen_memcg != NULL.
> select_victim_memcg() makes oc->chosen_memcg = INFLIGHT_VICTIM if there is
> inflight memcg. But oc->chosen_task remains NULL because it did not call
> oom_evaluate_task(), didn't it? (And if it called oom_evaluate_task(),
> put_task_struct() is missing here.) */
>
> + if (oom_kill_memcg_victim(oc)) {
>
> /* oom_kill_memcg_victim() returns true if oc->chosen_memcg == INFLIGHT_VICTIM. */
>
> + delay = true;
> + goto out;
> + }
> + }
> +
> select_bad_process(oc);
> /* Found nothing?!?! Either we hang forever, or we panic. */
> - if (!oc->chosen && !is_sysrq_oom(oc) && !is_memcg_oom(oc)) {
> + if (!oc->chosen_task && !is_sysrq_oom(oc) && !is_memcg_oom(oc)) {
> dump_header(oc, NULL);
> panic("Out of memory and no killable processes...\n");
> }
> - if (oc->chosen && oc->chosen != (void *)-1UL) {
> + if (oc->chosen_task && oc->chosen_task != (void *)-1UL) {
> oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
> "Memory cgroup out of memory");
> - /*
> - * Give the killed process a good chance to exit before trying
> - * to allocate memory again.
> - */
> - schedule_timeout_killable(1);
> + delay = true;
> }
> - return !!oc->chosen;
> +
> +out:
> + /*
> + * Give the killed process a good chance to exit before trying
> + * to allocate memory again.
> + */
> + if (delay)
> + schedule_timeout_killable(1);
> +
>
> /* out_of_memory() returns false because oc->chosen_task remains NULL. */
>
> + return !!oc->chosen_task;
> }
>
What about this fix Roman?
---
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 565e7da55318..fc06af041447 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -1174,7 +1174,7 @@ bool out_of_memory(struct oom_control *oc)
if (delay)
schedule_timeout_killable(1);
- return !!oc->chosen_task;
+ return !!(oc->chosen_task | oc->chosen_memcg);
}
/*
--
Michal Hocko
SUSE Labs
