linux-kernel - Re: [PATCH] mm: zswap: shrink until can accept

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Message-ID: <20230526135617.GA44890@cmpxchg.org>
Date:   Fri, 26 May 2023 09:56:17 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Vitaly Wool <vitaly.wool@...sulko.com>
Cc:     Domenico Cerasuolo <cerasuolodomenico@...il.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        sjenning@...hat.com, ddstreet@...e.org, yosryahmed@...gle.com,
        kernel-team@...com
Subject: Re: [PATCH] mm: zswap: shrink until can accept

On Fri, May 26, 2023 at 12:18:21PM +0200, Vitaly Wool wrote:
> On Wed, May 24, 2023 at 8:50 AM Domenico Cerasuolo
> > @@ -587,9 +587,13 @@ static void shrink_worker(struct work_struct *w)
> >  {
> >         struct zswap_pool *pool = container_of(w, typeof(*pool),
> >                                                 shrink_work);
> > +       int ret;
> >
> > -       if (zpool_shrink(pool->zpool, 1, NULL))
> > -               zswap_reject_reclaim_fail++;
> > +       do {
> > +               ret = zpool_shrink(pool->zpool, 1, NULL);
> > +               if (ret)
> > +                       zswap_reject_reclaim_fail++;
> > +       } while (!zswap_can_accept() && ret != -EINVAL);
> >         zswap_pool_put(pool);
> >  }
> 
> while I do agree with your points, I have a concern about this
> shrinker logic change. The reason for not doing this as you do was
> possible real time/responsiveness characteristics degrade. Have you
> checked that it's not really the case?

Good point. Adding a cond_resched() to the loop would be a good idea.