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Thu, 26 Mar 2026 05:37:43 -0700 (PDT) MIME-Version: 1.0 References: <20260325210637.3704220-1-shakeel.butt@linux.dev> <20260325190547.abb7309fb63473b57b7a90a0@linux-foundation.org> In-Reply-To: From: Kairui Song Date: Thu, 26 Mar 2026 20:37:06 +0800 X-Gm-Features: AQROBzDDhAwWy50_0AvWQXh7pN5XimsTxdhJS695rjfTsFhXBLoLPjM3epTli8o Message-ID: Subject: Re: [LSF/MM/BPF TOPIC] Towards Unified and Extensible Memory Reclaim (reclaim_ext) To: "Lorenzo Stoakes (Oracle)" Cc: Michal Hocko , Andrew Morton , Shakeel Butt , lsf-pc@lists.linux-foundation.org, Johannes Weiner , David Hildenbrand , Qi Zheng , Chen Ridong , Emil Tsalapatis , Alexei Starovoitov , Axel Rasmussen , Yuanchu Xie , Wei Xu , Matthew Wilcox , Nhat Pham , Gregory Price , Barry Song <21cnbao@gmail.com>, David Stevens , Vernon Yang , David Rientjes , Kalesh Singh , wangzicheng , "T . J . Mercier" , Baolin Wang , Suren Baghdasaryan , Meta kernel team , bpf@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: A6642A0014 X-Stat-Signature: snebziwskzu6iics6y5txwfak1eodekk X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1774528665-120610 X-HE-Meta: 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 U6IKUSRf 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Mar 26, 2026 at 4:02=E2=80=AFPM Lorenzo Stoakes (Oracle) wrote: > > On Thu, Mar 26, 2026 at 08:03:34AM +0100, Michal Hocko wrote: > > On Wed 25-03-26 19:05:47, Andrew Morton wrote: > > > On Wed, 25 Mar 2026 14:06:37 -0700 Shakeel Butt wrote: > > > > > > > We should unify both algorithms into a single code path. > > > > > > I'm here to ask the questions which others fear will sound dumb. > > > > Not dumb at all and recently discussed here https://lore.kernel.org/all= /CAMgjq7AkYOtUL2HuZjBu5dJw=3DRTL7W2L1+zVv=3DSCOyHKYwc3AA@mail.gmail.com/T/#= u > > > > > Is it indeed the plan to maintain both implementations? I thought th= e > > > long-term ambition was to knock MGLRU into shape and to drop the lega= cy LRU? > > > > Yes, but MGLRU is not there yet and with development pace last year or > > so we are not much closer than at the time MGLRU has been merged > > unfortunatelly. > > I'm quite concerned about maintainership, as it seems the MGLRU maintaine= rs have > not been all that active, and the MGLRU to me at least is currently a bla= ck box. > > I'm not the only one who's raised this (see [0]). > > That'd very much have to be resolved and the community reassured that MGL= RU is > _actively_ maintained before we could even contemplate it replacing the > 'classic' reclaim approach IMO. > > I hope that Kairu, Barry, Zicheng and others who are interested int it re= solve > this, however! Hi everyone, Right, I think we are starting to make good progress on improving MGLRU recently. For the last few years we already have some commits stashed downstream to enable that on our fleet, most of my effort in upstream is spent on other parts like SWAP, really looking forward to making MGLRU better upstreamly. Yesterday I was still discussing with CachyOS folks about their usage while working on that series for MGLRU cleanup and dirty flush optimization, and got some nice feedback later from their chat server that MGLRU's TTL resolved their thrashing issue very well. With classic LRU they needed a le9 patch downtreamly. For many other typical workloads under stress, MGLRU performs significantly better too (e.g. database, build kernel could be more than twice as fast), it would be a huge loss to leave it unmaintained. Barry also provided some really helpful ideas about MGLRU like readahead handling. We are also seeing other vendors and people contributing to MGLRU like Leno and Baolin recently. Things are looking promising.