On Mon, Aug 22, 2022 at 4:48 PM Andrew Morton [off-list ref] wrote:

On Mon, 22 Aug 2022 16:33:51 -0600 Yu Zhao [off-list ref] wrote:

quoted

quoted

--- a/mm/vmscan.c~mm-delete-unused-mmf_oom_victim-flag-fix
+++ a/mm/vmscan.c

@@ -3429,9 +3429,6 @@ static bool should_skip_mm(struct mm_str
        if (size < MIN_LRU_BATCH)
                return true;

-       if (mm_is_oom_victim(mm))
-               return true;
-
        return !mmget_not_zero(mm);
 }

@@ -4127,9 +4124,6 @@ restart:

                walk_pmd_range(&val, addr, next, args);

-               if (mm_is_oom_victim(args->mm))
-                       return 1;
-
                /* a racy check to curtail the waiting time */
                if (wq_has_sleeper(&walk->lruvec->mm_state.wait))
                        return 1;

_

Please confirm?

LGTM.  The deleted checks are not about correctness.

OK, for now.

quoted

I've queued

--- a/mm/vmscan.c
+++ b/mm/vmscan.c

@@ -3402,7 +3402,7 @@ static bool should_skip_mm(struct mm_struct *mm,

struct lru_gen_mm_walk *walk)
        if (size < MIN_LRU_BATCH)
                return true;

-       if (mm_is_oom_victim(mm))
+       if (test_bit(MMF_OOM_REAP_QUEUED, &mm->flags))
                return true;

        return !mmget_not_zero(mm);

@@ -4109,7 +4109,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned

long start, unsigned long end,

                walk_pmd_range(&val, addr, next, args);

-               if (mm_is_oom_victim(args->mm))
+               if (test_bit(MMF_OOM_REAP_QUEUED, &args->mm->flags))
                        return 1;

                /* a racy check to curtail the waiting time */

Oh.  Why?  What does this change do?

The MMF_OOM_REAP_QUEUED flag is similar to the deleted MMF_OOM_VICTIM
flag, but it's set at a later stage during an OOM kill.

When either is set, the OOM reaper is probably already freeing the
memory of this mm_struct, or at least it's going to. So there is no
need to dwell on it in the reclaim path, hence not about correctness.