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h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=atekYO+Zzto6OFwqsPBfWMn3kn5QaG4Z1k8V//4R4Odoz5R5yHsbyPLGbgdfu1rRF 86Dr0RmZMY95NzlxKdusVb71RogaLTXxusxen6iuQEmeAOg2fG54VCzy5uZuK9dItw yJgXxlQPPXNQ54Gvk2EkmTjvf5LsFKgJrgo5zZRM8QULA5k88HD9rV1IOwA8/sIzOJ cxPlrooUTHtPD6xX/lr17Uf5YDqZPN1YZ/akjFsJSt7Gg+rNWJsHXHvcqizPO9rLh4 druWXqhD8fQIQsgkekTDuC996ycwQFvBS/Zh8YTUe0CmF81RDccpjRzm2GgzFmaxcx EjXymvB6TD7Eg== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v6 08/15] mm/mglru: lift youngest gen protection for higher priority Reply-To: sashiko-reviews@lists.linux.dev To: =?utf-8?b?QmFycnkgU29uZyAoWGlhb21pKQ==?= , akpm@linux-foundation.org, linux-mm@kvack.org Cc: axelrasmussen@google.com, baolin.wang@linux.alibaba.com, baoquan.he@linux.dev, hannes@cmpxchg.org, hui.zhu@linux.dev, kasong@tencent.com, kunwu.chan@gmail.com, liam@infradead.org, lianux.mm@gmail.com, liuxiang.277@bytedance.com, lyugaofei@xiaomi.com, mhocko@kernel.org, mhocko@suse.com, qi.zheng@linux.dev, ridong.chen@linux.dev, rppt@kernel.org, ryncsn@gmail.com, shakeel.butt@linux.dev, surenb@google.com, wangzicheng@honor.com, weixugc@google.com, yuanchu@google.com, zhangbo56@xiaomi.com, zhuhui@kylinos.cn, sidchintamaneni@gmail.com In-Reply-To: <20261110202025.25736-9-baohua@kernel.org> References: <20261110202025.25736-1-baohua@kernel.org> <20261110202025.25736-9-baohua@kernel.org> Content-Type: text/plain; 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Sashiko AI review found 1 potential issue to consider: - [Low] mm/mglru: unfilled commit placeholder and stale description in changelog -- commit 357b36306d9c0f7d5cb9a3bda097730f4118d2a4 Author: Kairui Song mm/mglru: lift youngest gen protection for higher priority This commit adjusts the upper generation bound in scan_folios() based on reclaim priority so that the youngest generation is only scanned when sc->priority drops to or below DEF_PRIORITY / 2. > The problem is when aging can't catch up with reclaimer, reclaimers will > all abort early seeing there is only empty gens, or only two gens left. > Proactive aging won't help eigher because there will be limited threads > doing aging, but there could be unlimited threads doing reclaim, which > is a fundommental limitation of MGLRU. One way to avoid this is to use a > aging lock, like in commit .... However, aging lock caused several > jitter when under huge pressure, and was reported to be causing > obserable lags already on Android. > > What's more, the gen model somehow contradicts with the goal of > swappiness, which aim to reduce IO cost instead of following hotness > blindly. > > So instead, let's lift the protection based on priority. With default > priority, we still fully respect the MIN_NR_GEN protection. But as the > priority raised, allow it to reclaim younger gens step by step. [Severity: Low] Does the commit message match what this patch changes relative to earlier commit "mm/mglru: lift the forced protection of reclaimer" in the series? That earlier patch already removed the MIN_NR_GENS early return and allowed non-default priorities to scan up to lrugen->max_seq, whereas this patch restricts sc->priority > DEF_PRIORITY / 2 to lrugen->max_seq - 1 (and sets DEF_PRIORITY to lrugen->max_seq - MIN_NR_GENS) to keep protecting the youngest generation until severe pressure. Also, the second paragraph has = an unfilled "like in commit ...." placeholder and a few typos ("eigher", "fundommental", "obserable"). --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261110202025.2573= 6-1-baohua@kernel.org?part=3D8