linux-kernel - Re: [PATCH 1/2] mm/mglru: only clear kswapd

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Message-ID: <CAAPL-u8M4-i=76prAuRws1_Jvp3+fkYY3gHDgEpZ7VP45KY39Q@mail.gmail.com>
Date: Tue, 15 Oct 2024 22:29:11 -0700
From: Wei Xu <weixugc@...gle.com>
To: Yu Zhao <yuzhao@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Axel Rasmussen <axelrasmussen@...gle.com>, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm/mglru: only clear kswapd_failures if reclaimable

On Tue, Oct 15, 2024 at 9:57 PM Yu Zhao <yuzhao@...gle.com> wrote:
>
> On Mon, Oct 14, 2024 at 4:12 PM Wei Xu <weixugc@...gle.com> wrote:
> >
> > lru_gen_shrink_node() unconditionally clears kswapd_failures, which
> > can prevent kswapd from sleeping and cause 100% kswapd cpu usage even
> > when kswapd repeatedly fails to make progress in reclaim.
> >
> > Only clear kswap_failures in lru_gen_shrink_node() if reclaim makes
> > some progress, similar to shrink_node().
> >
> > Fixes: e4dde56cd208 ("mm: multi-gen LRU: per-node lru_gen_folio lists")
> > Signed-off-by: Wei Xu <weixugc@...gle.com>
> > ---
> >  mm/vmscan.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 50dc06d55b1d..9d1e1c4e383d 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -4970,8 +4970,8 @@ static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *
> >
> >         blk_finish_plug(&plug);
> >  done:
>
> Nit: the "done:" isn't used anymore, so better just remove it.
>

"goto done" is still used at the beginning of lru_gen_shrink_node().
We can refactor the code to remove it. But it is better to be handled
in a separate change.

> > -       /* kswapd should never fail */
> > -       pgdat->kswapd_failures = 0;
> > +       if (sc->nr_reclaimed > reclaimed)
> > +               pgdat->kswapd_failures = 0;
> >  }
> >
> >  /******************************************************************************
> > --
> > 2.47.0.rc1.288.g06298d1525-goog
> >
> >