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t=1794344203; bh=C59l5yjEcpPoOE77GBwwC572wfRdG0uqhTnZS6j/vg8=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=hb+T1JfWtIQLt9lEpnqY2Z0a2J8Ap9UFi+VmPb2nAHT4iwmQKPELs55EOatrtIkkn tJKXXMQEw6pK+INlMh6uP1ABEH5xvB5d4MnZL2aY6uhsjFWdcH21qCLsg+/wNHXDrq 4/F3swc4aQ9xmq+4mtKl5G8dFgYXaRBI5Wuxafmreu7lpgDa2TOpQHACvTUZazCR4v 6+vJ2AX3pwhs2mzF/rkAdFNHHQxNOP6xEw5OAxfEsymaf7en0bbRJCJs1Hk00wExlY ZSGapBfKclovo0brnvDDFZ/P/Yr5EEkuUzFvMmZzwWsIbYCm9dMeHhmXYOc6iTWbjT UwiUtcBkSIsDA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v6 09/15] mm/mglru: Avoid placing rejected folios below populated gen 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: <20261110202025.25736-10-baohua@kernel.org> References: <20261110202025.25736-1-baohua@kernel.org> <20261110202025.25736-10-baohua@kernel.org> Content-Type: text/plain; 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Sashiko AI review found no new issues in this patch, but noticed 1 related pre-existing issue it does not introduce: - [Medium] mm: uncleared LRU_REFS_FLAGS in lru_gen_add_folio() [1] -- commit 8ef17c06cc7c92ed5b07f7cf40e28066a3ac2fb0 Author: Barry Song (Xiaomi) mm/mglru: Avoid placing rejected folios below populated gen This commit passes the scanned generation sequence number from scan_folios() to move_folios_to_lru() so rejected folios are placed above the populated generation or in the youngest generation, and removes the previous folio_set_active() call from evict_folios(). > diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h > index ab69b9930893f..f6f4bc9a704fe 100644 > --- a/include/linux/mm_inline.h > +++ b/include/linux/mm_inline.h > @@ -332,7 +332,8 @@ static inline unsigned long lru_gen_folio_seq(const s= truct lruvec *lruvec, > return max(READ_ONCE(lrugen->max_seq) - gen + 1, READ_ONCE(lrugen->min_= seq[type])); > } > =20 > -static inline bool lru_gen_add_folio(struct lruvec *lruvec, struct folio= *folio, bool reclaiming) > +static inline bool __lru_gen_add_folio(struct lruvec *lruvec, struct fol= io *folio, > + unsigned long scanned_seq, bool reclaiming) > { > unsigned long seq; > unsigned long flags; > @@ -347,6 +348,8 @@ static inline bool lru_gen_add_folio(struct lruvec *l= ruvec, struct folio *folio, > return false; > =20 > seq =3D lru_gen_folio_seq(lruvec, folio, reclaiming); > + if (scanned_seq !=3D -1UL) > + seq =3D max(seq, min(scanned_seq + 1, lrugen->max_seq)); > gen =3D lru_gen_from_seq(seq); > flags =3D (gen + 1UL) << LRU_GEN_PGOFF; > /* see the comment on MIN_NR_GENS about PG_active */ [Severity: Medium] This problem wasn't introduced by this patch, but should set_mask_bits() in __lru_gen_add_folio() also clear LRU_REFS_FLAGS [1]? include/linux/mm_inline.h:__lru_gen_add_folio() { ... set_mask_bits(folio_flags(folio, 0), LRU_GEN_MASK | BIT(PG_active), flags); ... } Omitting LRU_REFS_FLAGS from the mask leaves stale PG_referenced and LRU_REFS_MASK bits set when a folio is placed into a new generation, inflating its tier access count and causing cold folios to be protected from reclaim at the expense of hotter ones. [1] https://sashiko.dev/#/bug/linux-d2209941-6149-4b37-a97a-08c70d875d2c --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261110202025.2573= 6-1-baohua@kernel.org?part=3D9