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From:   Joonsoo Kim <js1304@gmail.com>
Date:   Wed, 11 Mar 2020 16:27:44 +0900
Message-ID: <CAAmzW4PO1QeSpP=5S9AwVMc4NMnzkcB=2TgB3FSrttOVRWBxKg@mail.gmail.com>
Subject: Re: [PATCH v2 0/9] workingset protection/detection on the anonymous
 LRU list
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Johannes Weiner <hannes@cmpxchg.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 3=EC=9D=BC (=ED=99=94) =EC=98=A4=EC=A0=84 8:31, Jo=
onsoo Kim <js1304@gmail.com>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> 2020=EB=85=84 2=EC=9B=94 28=EC=9D=BC (=EA=B8=88) =EC=98=A4=EC=A0=84 8:36,=
 Andrew Morton <akpm@linux-foundation.org>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=
=84=B1:
> >
> > On Thu, 27 Feb 2020 08:48:06 -0500 Johannes Weiner <hannes@cmpxchg.org>=
 wrote:
> >
> > > > It sounds like the above simple aging changes provide most of the
> > > > improvement, and that the workingset changes are less beneficial an=
d a
> > > > bit more risky/speculative?
> > > >
> > > > If so, would it be best for us to concentrate on the aging changes
> > > > first, let that settle in and spread out and then turn attention to=
 the
> > > > workingset changes?
> > >
> > > Those two patches work well for some workloads (like the benchmark),
> > > but not for others. The full patchset makes sure both types work well=
.
> > >
> > > Specifically, the existing aging strategy for anon assumes that most
> > > anon pages allocated are hot. That's why they all start active and we
> > > then do second-chance with the small inactive LRU to filter out the
> > > few cold ones to swap out. This is true for many common workloads.
> > >
> > > The benchmark creates a larger-than-memory set of anon pages with a
> > > flat access profile - to the VM a flood of one-off pages. Joonsoo's
> > > first two patches allow the VM to usher those pages in and out of
> > > memory very quickly, which explains the throughput boost. But it come=
s
> > > at the cost of reducing space available to hot anon pages, which will
> > > regress others.
> > >
> > > Joonsoo's full patchset makes the VM support both types of workloads
> > > well: by putting everything on the inactive list first, one-off pages
> > > can move through the system without disturbing the hot pages. And by
> > > supplementing the inactive list with non-resident information, he can
> > > keep it tiny without the risk of one-off pages drowning out new hot
> > > pages. He can retain today's level of active page protection and
> > > detection, while allowing one-off pages to move through quickly.
> >
> > Helpful, thanks.
> >
> > At v2 with no evident review input I'd normally take a pass at this
> > stage.  But given all the potential benefits, perhaps I should be more
> > aggressive here?
>
> I hope so. It would boost the review. :)

Hello, Andrew.

Would you like to tell me your plan about this patchset?
Merging it into the next tree would accelerate the review and test. :)

Thanks.