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From:   Joonsoo Kim <js1304@gmail.com>
Date:   Fri, 13 Mar 2020 14:48:46 +0900
Message-ID: <CAAmzW4PW8Z7r7PoFUsAqSY9JpGB4iqxKodO5aath+2QrMSUeJg@mail.gmail.com>
Subject: Re: [PATCH v2 1/9] mm/vmscan: make active/inactive ratio as 1:1 for
 anon lru
To:     Johannes Weiner <hannes@cmpxchg.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Michal Hocko <mhocko@kernel.org>,
        Hugh Dickins <hughd@google.com>,
        Minchan Kim <minchan@kernel.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Mel Gorman <mgorman@techsingularity.net>, kernel-team@lge.com,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>
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2020=EB=85=84 3=EC=9B=94 12=EC=9D=BC (=EB=AA=A9) =EC=98=A4=ED=9B=84 11:47, =
Johannes Weiner <hannes@cmpxchg.org>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> On Thu, Feb 20, 2020 at 02:11:45PM +0900, js1304@gmail.com wrote:
> > From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> >
> > Current implementation of LRU management for anonymous page has some
> > problems. Most important one is that it doesn't protect the workingset,
> > that is, pages on the active LRU list. Although, this problem will be
> > fixed in the following patchset, the preparation is required and
> > this patch does it.
> >
> > What following patchset does is to restore workingset protection. In th=
is
> > case, newly created or swap-in pages are started their lifetime on the
> > inactive list. If inactive list is too small, there is not enough chanc=
e
> > to be referenced and the page cannot become the workingset.
> >
> > In order to provide enough chance to the newly anonymous pages, this pa=
tch
> > makes active/inactive LRU ratio as 1:1.
>
> Patch 8/9 is a revert of this patch. I assume you did this for the
> series to be bisectable and partially revertable, but I'm not sure
> keeping only the first and second patch would be safe: they reduce
> workingset protection quite dramatically on their own (on a 10G system
> from 90% of RAM to 50% e.g.) and likely cause regressions.
>
> So while patch 2 is probably a lot better with patch 1 than without,

Yes, it is what I intended.

> it seems a bit unnecessary since we cannot keep patch 2 on its own. We
> need the rest of the series to make these changes.

Yes, you're right.

> On the other hand, the patch is small and obviously correct. So no
> strong feelings either way.

Okay. I will keep the patches since I think that these patches will
help someone who want to understand the LRU management.

> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>
> Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>

Thanks!