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AJvYcCVSkEbzHlr2oyuQrtHpvzMjzhZ+uxnPGtmqMjVmNOPuId6OD9n4yrfBUwOEmURULgxqdnYxPn9eBQ==@kvack.org X-Gm-Message-State: AOJu0Yz03gTaSarqxrKDaNLySAcY50kw7v/g2Aiw+ZaV2gFIXAMRqcTv NPdAhYHM7pe9YtrL9uapdRTBgbAXPiYddhtkmVZXje4LpjLsIr77WqAp6gWNHEfWkvB28UCoAAq NQVh+dJk4Y0oZU303sYP0JPUAB56BJ0Q= X-Gm-Gg: ASbGncsdIp+aSlPC+ZEKx16OYFMvo8mYAHm5rmKAxOP+QWcjS0Z5soNZBhdwO/agzuo LgHthzJuA5hwFZXmcRBKT005fptyru2FnggGGgnqceZrBfVDZFmN1oYa+RkQ7e2FcPGnQ3OqMIl 1ZaF447C1YHc7BaAqkcmmD3NvwCkrfilfbDmGwD6Nv3TneZWnv9HUrJBnD9cKJaCBei6//6BgIW cifmkT2n5E/kA/w/pLC26HQeWDvQd7whakrwCrmww224kG85/A+NVSUq/pApG1t0VKLeg== X-Google-Smtp-Source: AGHT+IFQFaTlSgrkPrDF34ZzuXXc6tRWv7IWzSI1FLwFBEaeyfWtvk4amHL87+8261TG5sC/U7niA6iwfCoFudViaSk= X-Received: by 2002:a05:6102:919:b0:5db:f15a:539d with SMTP id ada2fe7eead31-5e22423f36emr8227948137.7.1764562451234; Sun, 30 Nov 2025 20:14:11 -0800 (PST) MIME-Version: 1.0 References: <20251128025315.3520689-1-wangzicheng@honor.com> In-Reply-To: From: Barry Song <21cnbao@gmail.com> Date: Mon, 1 Dec 2025 12:13:59 +0800 X-Gm-Features: AWmQ_bnCsLVtTt2xe_A-3mmx3kROTPC9EO7s9FoipJAT7VnWafh4GCqMSpp-xoE Message-ID: Subject: Re: [PATCH 0/3] mm/lru_gen: move lru_gen control interface from debugfs to procfs To: "Liam R. Howlett" , Matthew Wilcox , Zicheng Wang , akpm@linux-foundation.org, hannes@cmpxchg.org, david@redhat.com, axelrasmussen@google.com, yuanchu@google.com, mhocko@kernel.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, lorenzo.stoakes@oracle.com, weixugc@google.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, corbet@lwn.net, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 46B0B1A000D X-Stat-Signature: o7sr617xxbuksmpnqymix8roxo8399hw X-Rspam-User: X-HE-Tag: 1764562452-56423 X-HE-Meta: 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 w3wKHo2F 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Liam, I saw you mentioned me, so I just wanted to join in :-) On Sat, Nov 29, 2025 at 12:16=E2=80=AFAM Liam R. Howlett wrote: > > * Matthew Wilcox [251128 10:16]: > > On Fri, Nov 28, 2025 at 10:53:12AM +0800, Zicheng Wang wrote: > > > Case study: > > > A widely observed issue on Android is that after application launch, > > What do you mean by application launch? What does this mean in the > kernel context? I think there are two cases. First, a cold start: a new process is forked to launch the app. Second, when the app switches from background to foreground, for example when we bring it back to the screen after it has been running in the background. In the first case, you reboot your phone and tap the YouTube icon to start the app (cold launch). In the second case, you are watching a video in YouTube, then switch to Facebook, and later tap the YouTube icon again to bring it from background to foreground. > > > > the oldest anon generation often becomes empty, and file pages > > > are over-reclaimed. > > > > You should fix the bug, not move the debug interface to procfs. NACK. > > Barry recently sent an RFC [1] to affect LRU in the exit path for > Android. This was proven incorrect by Johannes, iirc, in another thread > I cannot find (destroys performance of calling the same command). My understanding is that affecting the LRU in the exit path is not generally correct, but it still highlights a requirement: Linux LRU needs a way to understand app-cycling behavior in an Android-like system. > > These ideas seem both related as it points to a suboptimal LRU in the > Android ecosystem, at least. It seems to stem from Androids life > (cycle) choices :) > > I strongly agree with Willy. We don't want another userspace daemon > and/or interface, but this time to play with the LRU to avoid trying to > define and fix the problem. > > Do you know if this affects others or why it is android specific? The behavior Zicheng probably wants is a proactive memory reclamation interface. For example, since each app may be in a different memcg, if an app has been in the background for a long time, he wants to reclaim its memory proactively rather than waiting until kswapd hits the watermarks. This may help a newly launched app obtain memory more quickly, avoiding delays from reclamation, since a new app typically requires a substantial amount of memory. Zicheng, please let me know if I=E2=80=99m misunderstanding anything. > > [1]. https://lore.kernel.org/all/20250514070820.51793-1-21cnbao@gmail.co= m/ > Thanks Barry