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t=1794459669; bh=rGnqvBfwv1GuzgofDivUXLxhCclkpqt3OTX1NYXZgCg=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=CE6YXn7bKsphjp6X4RUj+o8yYThu4S1WjytVLPUav9DUmivny2qiLJErTxBlUAhlP 1Cde7MzHMXfg/MvZQyo+i1hAq1tw0Lht+9DCtJyejOXXKIxWnJh/8eoOmD6BfNhIh2 RwklVmnwKiTZXeWv5pzCc7OKdMnLj1fGazNp3QI6hnE4RCxXRxxR+NOORa6dYDp8Pt Uvg2fqsBipG7xyYi9sDEtNrUO+B3Afi2hySmrMu7NThyDPWSqrNOxiAzG0WSFw7E/2 fiD0eCxlLjBt5TqwdAIueQ53vT3397zDB7eUL5Rh7kf4+ZW/gP+betR80D8EkqeDJW UOq18IhjWFdAA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v7 12/16] mm/mglru: Restrict eviction accounting to eligible zones Reply-To: sashiko-reviews@lists.linux.dev To: =?utf-8?b?QmFycnkgU29uZyAoWGlhb21pKQ==?= , akpm@linux-foundation.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, linux-mm@kvack.org, 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: <20261111232603.9934-13-baohua@kernel.org> References: <20261111232603.9934-1-baohua@kernel.org> <20261111232603.9934-13-baohua@kernel.org> Content-Type: text/plain; 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Sashiko AI review found 1 potential issue to consider: - [High] mm/mglru: premature OOM kill in lru_gen_age_node() on zone-constrained reclaim -- commit 169c51ce627ac19052dda882e181615f7e7c984d Author: Barry Song (Xiaomi) mm/mglru: Restrict eviction accounting to eligible zones This commit restricts lruvec_evictable_size() and lru_gen_imbalanced() to count only zones at or below sc->reclaim_idx by adding a max_zone parameter to lruvec_gen_size(). > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 41dd77652c82f..8b77e6bc1d519 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -4207,8 +4207,8 @@ static void set_initial_priority(struct pglist_data= *pgdat, struct scan_control > sc->priority =3D clamp(priority, DEF_PRIORITY / 2, DEF_PRIORITY); > } > =20 > -static void lruvec_evictable_size(struct lruvec *lruvec, int swappiness, > - unsigned long nr[]) > +static void lruvec_evictable_size(struct lruvec *lruvec, struct scan_con= trol *sc, > + int swappiness, unsigned long nr[]) > { > int type; > unsigned long seq; > @@ -4221,7 +4221,7 @@ static void lruvec_evictable_size(struct lruvec *lr= uvec, int swappiness, > =20 > for_each_evictable_type(type, swappiness) { > for (seq =3D min_seq[type]; seq <=3D max_seq; seq++) > - nr[type] +=3D lruvec_gen_size(lrugen, type, seq); > + nr[type] +=3D lruvec_gen_size(lrugen, type, seq, sc->reclaim_idx + 1); > } > } > =20 > @@ -4230,7 +4230,7 @@ static bool lruvec_is_sizable(struct lruvec *lruvec= , struct scan_control *sc) > unsigned long total, sizes[ANON_AND_FILE]; > int swappiness =3D get_swappiness(lruvec, sc); > =20 > - lruvec_evictable_size(lruvec, swappiness, sizes); > + lruvec_evictable_size(lruvec, sc, swappiness, sizes); > total =3D sizes[LRU_GEN_ANON] + sizes[LRU_GEN_FILE]; > =20 > /* whether the size is big enough to be helpful */ [Severity: High] Can restricting lruvec_is_sizable() to sc->reclaim_idx trigger a premature global OOM kill in lru_gen_age_node() during zone-constrained reclaim when lru_gen_min_ttl is enabled? In balance_pgdat(), kswapd sets sc.reclaim_idx =3D highest_zoneidx and runs kswapd_age_node() -> lru_gen_age_node() before kswapd_shrink_node(): mm/vmscan.c:lru_gen_age_node() { ... do { struct lruvec *lruvec =3D mem_cgroup_lruvec(memcg, pgdat); mem_cgroup_calculate_protection(NULL, memcg); if (!reclaimable) reclaimable =3D lruvec_is_reclaimable(lruvec, sc, min_ttl); } while ((memcg =3D mem_cgroup_iter(NULL, memcg, NULL))); ... if (!reclaimable && mutex_trylock(&oom_lock)) { struct oom_control oc =3D { .gfp_mask =3D sc->gfp_mask, }; out_of_memory(&oc); mutex_unlock(&oom_lock); } } Because user LRU pages are allocated from the highest zones and kept out of lower zones by lowmem_reserve, a wakeup with a constrained highest_zoneidx (such as ZONE_DMA or ZONE_DMA32) can find fewer than 1UL << sc->priority evictable pages in zones 0..sc->reclaim_idx in every memcg. lruvec_is_sizable() and lruvec_is_reclaimable() then return false for all memcgs, causing lru_gen_age_node() to invoke out_of_memory() with GFP_KERNEL even when higher zones have plenty of reclaimable memory older than min_ttl. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261111232603.9934= -1-baohua@kernel.org?part=3D12