linux-kernel - Re: [PATCH RESEND v2 2/2] mm: delete unused MMF_OOM

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Message-Id: <20220822154822.366a9e4527b748cf99d98637@linux-foundation.org>
Date:   Mon, 22 Aug 2022 15:48:22 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Yu Zhao <yuzhao@...gle.com>
Cc:     Suren Baghdasaryan <surenb@...gle.com>,
        Michal Hocko <mhocko@...e.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, Minchan Kim <minchan@...nel.org>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andrea Arcangeli <aarcange@...hat.com>, brauner@...nel.org,
        hch@...radead.org, oleg@...hat.com,
        David Hildenbrand <david@...hat.com>,
        Jann Horn <jannh@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Peter Xu <peterx@...hat.com>,
        John Hubbard <jhubbard@...dia.com>, shuah@...nel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>, linux-kselftest@...r.kernel.org,
        kernel-team@...roid.com
Subject: Re: [PATCH RESEND v2 2/2] mm: delete unused MMF_OOM_VICTIM flag

On Mon, 22 Aug 2022 16:33:51 -0600 Yu Zhao <yuzhao@...gle.com> wrote:

> > --- 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.

> 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?