linux-kernel - Re: [PATCH] mm: fix LRU balancing effect of new transparent huge pages

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Date:   Mon, 11 May 2020 15:04:01 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Mel Gorman <mgorman@...e.de>, Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, Michal Hocko <mhocko@...nel.org>,
        Minchan Kim <minchan@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: fix LRU balancing effect of new transparent huge pages

On Mon, May 11, 2020 at 2:58 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Mon, 11 May 2020 14:38:23 -0700 Shakeel Butt <shakeelb@...gle.com> wrote:
>
> > On Mon, May 11, 2020 at 2:11 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
> > >
> > > On Sat,  9 May 2020 07:19:46 -0700 Shakeel Butt <shakeelb@...gle.com> wrote:
> > >
> > > > Currently, THP are counted as single pages until they are split right
> > > > before being swapped out. However, at that point the VM is already in
> > > > the middle of reclaim, and adjusting the LRU balance then is useless.
> > > >
> > > > Always account THP by the number of basepages, and remove the fixup
> > > > from the splitting path.
> > >
> > > Confused.  What kernel is this applicable to?
> >
> > It is still applicable to the latest Linux kernel.
>
> The patch has
>
> > @@ -288,7 +288,7 @@ static void __activate_page(struct page *page, struct lruvec *lruvec,
> >
> >               __count_vm_events(PGACTIVATE, nr_pages);
> >               __count_memcg_events(lruvec_memcg(lruvec), PGACTIVATE, nr_pages);
> > -             update_page_reclaim_stat(lruvec, file, 1);
> > +             update_page_reclaim_stat(lruvec, file, 1, nr_pages);
> >       }
> >  }
>
> but current mainline is quite different:
>
> static void __activate_page(struct page *page, struct lruvec *lruvec,
>                             void *arg)
> {
>         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
>                 int file = page_is_file_lru(page);
>                 int lru = page_lru_base_type(page);
>
>                 del_page_from_lru_list(page, lruvec, lru);
>                 SetPageActive(page);
>                 lru += LRU_ACTIVE;
>                 add_page_to_lru_list(page, lruvec, lru);
>                 trace_mm_lru_activate(page);
>
>                 __count_vm_event(PGACTIVATE);
>                 update_page_reclaim_stat(lruvec, file, 1);
>         }
> }
>
> q:/usr/src/linux-5.7-rc5> patch -p1 --dry-run < ~/x.txt
> checking file mm/swap.c
> Hunk #2 FAILED at 288.
> Hunk #3 FAILED at 546.
> Hunk #4 FAILED at 564.
> Hunk #5 FAILED at 590.
> Hunk #6 succeeded at 890 (offset -9 lines).
> Hunk #7 succeeded at 915 (offset -9 lines).
> Hunk #8 succeeded at 958 with fuzz 2 (offset -10 lines).
> 4 out of 8 hunks FAILED
>

Oh sorry my mistake. It is dependent on the first two patches at [1].
Basically I replaced the third patch of the series with this one. I
should have re-send them all together.

[1] http://lkml.kernel.org/r/20200508212215.181307-1-shakeelb@google.com