From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794686919; b=1rkeeozDYRCgzoI5GAH6x+dk+YivlfYAPjMnl0Lkv2KgYKmWpU9VdMiKu2yb46YY6Tc0 sOvdAmdRFIMHrvnStEyxjP1JtQ/el6TsH2UVJm//eaTvpVn6vtJXkLyxEBeDBOmW4+lxd BOLXGlUmg0RSKSOYYI9cu6IrvKR22ip5B0GILoO44WkeNSD1TpdSBL7C9Jo2OoPBTK/oi U9xwmhgpUFafp8SDA5wtTad8t294GXCAtYu5kweZVHXkG6kQFR6cz8OMCAwqgkRGA6TRu 5qALRVJ39eMJEMre9Udwd7ZQ0AZL5Nt6NP2rFhIaFfncmfPsrPHKPSzdq+ZtIiMb54w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794686919; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-Id:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=2o3SI4bwFrc7bAbrnsYUQ3EEpOSbHBMvTUqeawpBv4A=; b=sjUqSNWY3r6Nl8tMYNn7DxD6g0bFX2zB3WJrc0A/8uqKyr1Sxbocee6Oy2ZLx59bvZpI hMIldCHaKTIqdYIiQddDl+7A8db8WjfTiE3WurQmqcuHHqd07qI/hbTgOg8KZtxK6hV/4 Hd/zNwovo67OD5FnrEqRw7BPpU74GoXxR9lVs/+4C7iJFVhzAD85ZQsZy26swyCf/zyzf rm4iU/bQpa98Ar5I7u+hMywzYSZnImWPRnpxFPrsCCdRGhstq6+puXDKPzicbR/FDPLS9 aONVykJZKPZCLPgdmhic/O10rXMcb8B2KJQtu3xIGZYoahFQej8ann8Xd805t+H4lSg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="Bh/GgWO7"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3DD2A606A32E for ; Sat, 14 Nov 2026 20:08:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Bh/GgWO7 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 133B51F000CA; Sat, 14 Nov 2026 20:08:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794686918; bh=2o3SI4bwFrc7bAbrnsYUQ3EEpOSbHBMvTUqeawpBv4A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Bh/GgWO7fMNO0NDCxtGb7jqy2fJNZoLZLPmqXU2ZRlVUVm61JiCI0eMV8KuSLTgRc 24U4jckx8mZATuDBT+UVQLrpJs+e4V0OmVVi/MTVnWkDY6AJE6L4l5tVV8phsCCkpC azQyDMnI33Tdd6Yx5xx7BSi60eHXSkdSho1TYU7bSgo+zMNMIe2pNvajP3cAcGie0q YHEUDpwuXZe6tu7q8ol1zWFA9sGrG4nDCZFrHGFDFCGZ5MusiVfu6kzr1VENNeU07F dT3fy9swpMZbJeel6XgHoPVB3fNT/snacV7ChLCNQNEZrl4cespRUpU/Fh1wV3whjv 1pJA8WKmXD8bA== From: "Barry Song (Xiaomi)" To: 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, linux-kernel@vger.kernel.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, Barry Song Subject: [PATCH v9 05/16] mm/mglru: skip zones above reclaim_idx instead of rotating them Date: Sun, 15 Nov 2026 04:07:52 +0800 Message-Id: <20261114200803.23129-6-baohua@kernel.org> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20261114200803.23129-1-baohua@kernel.org> References: <20261114200803.23129-1-baohua@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Kairui Song scan_folios() used to visit every zone. Folios in zones above sc->reclaim_idx can never be isolated, so sort_folio() rotated them to a younger generation, the "ineligible" branch, or, when only one gen was left, skipped them. This wasted scan work on every pass, and the rotation kept the protected folios from aging. Restrict both the scan and the gen selection to the eligible zones, like the legacy LRU, which only isolates folios in zones up to reclaim_idx: - lruvec_populated_min_seq() takes a zone_limit, so the oldest populated gen is searched only among the zones the scan can reclaim from. A gen populated only in protected zones no longer stalls the scan. - scan_folios() iterates the eligible zones in the descending order of the legacy zonelist walk, draining the zone at reclaim_idx first. - The ineligible branch of sort_folio() is now dead and removed, with a VM_WARN_ON_ONCE_FOLIO() guarding the new invariant. try_to_inc_min_seq() still considers all zones, so min_seq[type] is only bumped once the oldest gen is empty everywhere. At DEF_PRIORITY the search bound stays min_seq[type], so the scan still starts from the oldest gen regardless of whether it is populated. Signed-off-by: Kairui Song Signed-off-by: Barry Song (Xiaomi) --- mm/vmscan.c | 47 +++++++++++++++++++---------------------------- 1 file changed, 19 insertions(+), 28 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 603fb7c73f94..b3ce4a550a62 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3992,7 +3992,7 @@ static bool inc_min_seq(struct lruvec *lruvec, int type, int swappiness) /* Similar to lruvec_evictable_size, return the oldest populated seq of the type */ static unsigned long lruvec_populated_min_seq(struct lruvec *lruvec, int type, - unsigned long max_seq) + int zone_limit, unsigned long max_seq) { int gen, zone; unsigned long min_seq; @@ -4003,7 +4003,7 @@ static unsigned long lruvec_populated_min_seq(struct lruvec *lruvec, int type, min_seq = READ_ONCE(lrugen->min_seq[type]); while (min_seq < max_seq) { gen = lru_gen_from_seq(min_seq); - for (zone = 0; zone < MAX_NR_ZONES; zone++) { + for (zone = 0; zone < zone_limit; zone++) { if (!list_empty(&lrugen->folios[gen][type][zone])) return min_seq; } @@ -4026,7 +4026,7 @@ static void try_to_inc_min_seq(struct lruvec *lruvec, int swappiness) /* Requires at least MIN_NR_GENS gens for basic functionality */ seq = lrugen->max_seq - MIN_NR_GENS; for_each_evictable_type(type, swappiness) { - min_seq[type] = lruvec_populated_min_seq(lruvec, type, seq + 1); + min_seq[type] = lruvec_populated_min_seq(lruvec, type, MAX_NR_ZONES, seq + 1); if (min_seq[type] > lrugen->min_seq[type]) seq_inc_flag = true; } @@ -4689,6 +4689,7 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c struct lru_gen_folio *lrugen = &lruvec->lrugen; VM_WARN_ON_ONCE_FOLIO(gen >= MAX_NR_GENS, folio); + VM_WARN_ON_ONCE_FOLIO(zone > sc->reclaim_idx, folio); /* unevictable: let it through and the generic path will cull it */ if (!folio_evictable(folio)) @@ -4705,10 +4706,8 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c * longer be promoted or protected, so just isolate them. The one * exception is lru_gen_reparent_memcg(), which is handled above. */ - if (min_gen == max_gen) { - VM_WARN_ON_ONCE(zone > sc->reclaim_idx); + if (min_gen == max_gen) return false; - } /* protected */ if (tier > tier_idx || refs + workingset == BIT(LRU_REFS_WIDTH) + 1) { @@ -4725,13 +4724,6 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c return true; } - /* ineligible */ - if (zone > sc->reclaim_idx) { - gen = folio_inc_gen(lruvec, folio, min_gen); - list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]); - return true; - } - return false; } @@ -4763,16 +4755,17 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec, struct scan_control *sc, int type, int tier, struct list_head *list, int *isolatedp) { - int i; enum node_stat_item item; + int zone_idx; int sorted = 0; int scanned = 0; int isolated = 0; int skipped = 0; int gen, max_gen; - unsigned long min_seq; + unsigned long seq; unsigned long remaining = nr_to_scan; struct lru_gen_folio *lrugen = &lruvec->lrugen; + struct pglist_data *pgdat = lruvec_pgdat(lruvec); DEFINE_MAX_SEQ(lruvec); VM_WARN_ON_ONCE(nr_to_scan > MAX_LRU_BATCH); @@ -4784,24 +4777,22 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec, * when under pressure to respect swappiness more and reduce IO cost. */ if (sc->priority == DEF_PRIORITY) - min_seq = lrugen->min_seq[type]; + seq = lrugen->min_seq[type]; else - min_seq = lruvec_populated_min_seq(lruvec, type, lrugen->max_seq); + seq = lrugen->max_seq; - gen = lru_gen_from_seq(min_seq); + seq = lruvec_populated_min_seq(lruvec, type, sc->reclaim_idx + 1, seq); + gen = lru_gen_from_seq(seq); max_gen = lru_gen_from_seq(max_seq); - for (i = MAX_NR_ZONES; i > 0; i--) { + /* Scan eligible zones in descending order. */ + for (zone_idx = sc->reclaim_idx; zone_idx >= 0; zone_idx--) { LIST_HEAD(moved); int skipped_zone = 0; - int zone = (sc->reclaim_idx + i) % MAX_NR_ZONES; - struct list_head *head = &lrugen->folios[gen][type][zone]; + struct zone *zone = &pgdat->node_zones[zone_idx]; + struct list_head *head = &lrugen->folios[gen][type][zone_idx]; - /* - * If there is only one gen left, rotating the unreclaimable - * zone become meaningless, just skip them. - */ - if (gen == max_gen && zone > sc->reclaim_idx) + if (!managed_zone(zone)) continue; while (!list_empty(head)) { @@ -4811,7 +4802,7 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec, VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio); VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio); VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio); - VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio); + VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone_idx, folio); scanned += delta; if (sort_folio(lruvec, folio, sc, gen, max_gen, tier)) @@ -4830,7 +4821,7 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec, if (skipped_zone) { list_splice(&moved, head); - __count_zid_vm_events(PGSCAN_SKIP, zone, skipped_zone); + __count_zid_vm_events(PGSCAN_SKIP, zone_idx, skipped_zone); skipped += skipped_zone; } -- 2.39.3 (Apple Git-146)