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Mercier" Date: Fri, 26 Jan 2024 08:41:30 -0800 Message-ID: Subject: Re: [PATCH] Revert "mm:vmscan: fix inaccurate reclaim during proactive reclaim" To: Johannes Weiner Cc: Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , android-mm@google.com, yuzhao@google.com, yangyifei03@kuaishou.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 212344001F X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 5o6usneqsdgebanxwgxx8gn3rmkzs5fu X-HE-Tag: 1706287302-726765 X-HE-Meta: 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 czH1zDO3 em+uNd2unzZ/xpAdSt0xl6yNuKfyIWdjjaf6Z7Vv/5GrMK2vRBLkAdZjI5arwf8FU2uLUDwdDRaTRSsmyUDasC5jzd9Aah5u3UeuE8e2QqUCiwp1WPCaOyf+kFtr+8/pbIElkW7Hfi6BmHjK9uvxPHQzmSZLSxketVYkGBcytH3CnmEtM7ew57BNrilQxP0GPv6GaLl7W2NeFokhV6UOQH83TjzLbKPPsKtbgltCtLUmeky6vvA7dCcblhW243jFfb1bC+y6aTeYYxErx1P2HZ6tse/WFwfnTlzQq X-Bogosity: Ham, tests=bogofilter, spamicity=0.001912, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jan 26, 2024 at 8:34=E2=80=AFAM Johannes Weiner wrote: > > On Wed, Jan 24, 2024 at 09:46:23AM -0800, T.J. Mercier wrote: > > In the meantime, instead of a revert how about changing the batch size > > geometrically instead of the SWAP_CLUSTER_MAX constant: > > > > reclaimed =3D try_to_free_mem_cgroup_pages(memcg, > > - min(nr_to_reclaim - > > nr_reclaimed, SWAP_CLUSTER_MAX), > > + (nr_to_reclaim - nr_reclaimed)/= 2, > > GFP_KERNEL, reclaim_options); > > > > I think that should address the overreclaim concern (it was mentioned > > that the upper bound of overreclaim was 2 * request), and this should > > also increase the reclaim rate for root reclaim with MGLRU closer to > > what it was before. > > Hahaha. Would /4 work for you? > > I genuinely think the idea is worth a shot. /4 would give us a bit > more margin for error, since the bailout/fairness cutoffs have changed > back and forth over time. And it should still give you a reasonable > convergence on MGLRU. > > try_to_free_reclaim_pages() already does max(nr_to_reclaim, > SWAP_CLUSTER_MAX) which will avoid the painful final approach loops > the integer division would produce on its own. > > Please add a comment mentioning the compromise between the two reclaim > implementations though. I'll try it out and get back to you. :)