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=1794596174; b=G33CCy9qgA8n2lgzU5BNRhq5+HKfO/GMPrEQeUoKPmuGGdjYC4iC2Z/CtTlYNgNoQed3 WHxipK2ndYySvBQObNVRc33eRWmOmARYFGqlWt9CIMMVmCGsKQHVjJlAEpLaus9tP83jx HINEKeuX0picdzwAP8kqIz/+exfQ93UVuOlJeyTlB8VuIP7K4bA84X+xFf+2zQRZmYvoM 1hgY5FUqTovMpCXEG+UiuiJEEziSmQoOZ2fp7CBOcytitELID21dFFmbwvsC3q8WMkbdy fMYwv9hG3XnQSRuwcbXFF5UYYVrY4HmF8Mpt3DG+7Yd9FCUTgAsnRxinCk6dgTCZnvQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794596174; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-Id:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=CFBgz9a6PFaeiektq38l4AMQg2WGrNsoRVRJuqkI91Y=; b=WDhsBoGa4zLeJt5/oIhAgw+jj6UAoxXnGg5YV7C+RoAlZTBZVjYRj/Tg26l31Acou90B WOhoTxG0nS+d8XCk+mb3+hFzrLowR9BPuhLlVYU8seTXhcwHSdYt5KwHe6UWkA0XO7JBZ DJhRWHXItlFVpkPf5HEiAAF4N8QVwoFWwDzz7j4KI0vyLHy1Hm+M4Hx2C4YwDCoITTYC+ ThKo9/2k/W+WJbr4DZ4693kBmIB0uuB9nlWZvUKC4qpn6f6lTQMHekxY+7yh9kiWpi4Q9 Ghvf4PhkjwRT4gt/GUCX352iX/8zDDP95VuRvATqecUj3zEF7rN8t1kQr5Hmtm0yr0Q== 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=cEAr2HQs; 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 899C56071040 for ; Fri, 13 Nov 2026 18:56:14 +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=cEAr2HQs Received: by smtp.kernel.org (Postfix) with ESMTPSA id 84B1A1F000C5; Fri, 13 Nov 2026 18:56:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794596174; bh=CFBgz9a6PFaeiektq38l4AMQg2WGrNsoRVRJuqkI91Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cEAr2HQsZ1HHjKxIxtST4/NiLm1Wyc+KIlItjQzOcfqY4hu5Up643evmj4GyrtiMS Vmget5swEPwDuETHXtENzVK7cop367Y+vCrQRjVKr9/r6w5IPPj6Nu0t7iks9jB9xB 54lFYd8qrBvUvp/cFDJxeQYA8xMsQSm9QHU8+cM1JovcYqJBFxfd1aMDzzK57Q5xlK +/mPscj9NRkLLkP+/OUqeAhkXINVdceKIv7zjqKTaSCLVtt3m0QQEoMswGKd++D3sl XK2MDBNAb9E1FcpXxWMVQCsbkK56bTAu85pFBjaV0u2VjicjXs4eyiyObhBIL6tgUt Vum8wnlpS71lg== 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 v8 05/16] mm/mglru: skip zones above reclaim_idx instead of rotating them Date: Sat, 14 Nov 2026 02:55:30 +0800 Message-Id: <20261113185541.70203-6-baohua@kernel.org> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20261113185541.70203-1-baohua@kernel.org> References: <20261113185541.70203-1-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 0e8b3161f8f5..a6e9e755e4b2 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)