From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id B4FAB606B2E4 for ; Fri, 13 Nov 2026 18:56:38 +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=dkhTZgJI Received: by kanga.kvack.org (Postfix) id C5CBF6B05C0; Fri, 13 Nov 2026 13:56:37 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C3ABE6B05C6; Fri, 13 Nov 2026 13:56:37 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AADE76B05C7; Fri, 13 Nov 2026 13:56:37 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 77B766B05C0 for ; Fri, 13 Nov 2026 13:56:37 -0500 (EST) Received: from smtpin23.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id E4CC11C28CE for ; Fri, 13 Nov 2026 18:56:36 +0000 (UTC) X-FDA: 85431001992.23.449588A Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf31.hostedemail.com (Postfix) with ESMTP id 501AF20003 for ; Fri, 13 Nov 2026 18:56:35 +0000 (UTC) Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=dkhTZgJI; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf31.hostedemail.com: domain of baohua@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=baohua@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1794596195; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ajYCha50EQl9+H9M7bL6r/fZ9jHUuzU39/jgu1TzRj8=; b=5y1jYTkCL6SPnxzsrg8LBXIm3fX2wKTd3X3ziscYdXV3icLeV8fSOmgxXLxYGIQaxSrQqw f9z3yeiPD+OMz9j3Dy5XO+fX69j1CgBQX03Iga00l6nXwiOF5MqiiOSaZv+L/6AI7cJkJa lm9s4OSaYxFM/HoUBk67bXXQ31OBGs0= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1794596195; b=3EE5n9HSOghDPEyf4Qz4pdgHIJjzpxXE9OgIFV8S9jCqKQmNs687RHIAwvGJzT9tsO+vbh 4wfxRqyB8jInfQF7wc+7leTl1JNf+aBkl4jl3sPY74IOAWDlINu/eG4LyhIOeL+ov+JuUE gmHJ0ob2QM7V6Z96sVRZgSojoO/foJQ= ARC-Authentication-Results: i=1; imf31.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=dkhTZgJI; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf31.hostedemail.com: domain of baohua@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=baohua@kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id E55D163319; Fri, 13 Nov 2026 18:56:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E92F51F000C8; Fri, 13 Nov 2026 18:56:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794596194; bh=ajYCha50EQl9+H9M7bL6r/fZ9jHUuzU39/jgu1TzRj8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=dkhTZgJIIEUYH1c/lcXkoBppbQxdmPhTzdGaU2x30T6mSbIRIL5f4s4hx5y7EXsZm zp47oGjg6t3aU/+ZkhKa6UmOb09x6s010eQorIL85vCila2VHtWUMcvjUmirJBY5KH KAn6EadC1n9w/KSGZHKpwIucHo09xPfB4N3enqRadnEqz8Idj6z4M6O4LkdLosvDc+ LvhiL4lFvLhfRg3vxu9XfC1nhG5xS6oO/JQFfm8plwg1w7C30a1HQAJsNs6fYljDsy 6T1TzSMG2tM9wrBRw8I+3z7QyXhT+lerdMHjME5OPFibqMV7IFh0aeyzEpfQK6LpFl GCMXWfPG4CVZQ== 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 (Xiaomi)" Subject: [PATCH v8 09/16] mm/mglru: Avoid placing rejected folios below populated gen Date: Sat, 14 Nov 2026 02:55:34 +0800 Message-Id: <20261113185541.70203-10-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-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: mn5tppxoaap1bq7w6pms6zwyiazk3dtk X-Rspam-User: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 501AF20003 X-HE-Tag: 1794596195-653054 X-HE-Meta: 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 TQu0ow8P e2RVmKYvmB7yGvwKRvSiHrIPgAdwJLt0cZxjsj487hgkjMVnUkMib22VF/fFSJ4PrUJ3wTkEJ6OBwb2tsmoImdKXacTR7V5CIspqQj3V53hkVUaoKvKvcuNBv2MecbDOg/JSYcmSCvNeZK3uy8YwG+GmtXZkitOjT03Pzulp7YHHhsRAd5dkMYciAsBs1i4XBv9kxjOSKFYAFy814bGsinULdS52ffBFR/BCPXWoWdjvSyP2PeRUGAFGv7rIzz7tfkmTji+HEV1b6luYkKXOu8GP/P/HqQacqbM94W0pGITXf0wHW9JJHlUddaf7iT/dQpU1T8rdf0RhM9ZY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 We used to scan only the oldest generation in scan_folios(). In evict_folios(), we checked whether lru_gen_folio_seq(lruvec, folio, false) == min_seq[type]. If so, the folio was marked active and moved to younger generations. This was itself buggy, as folios in generation min_seq[type] - 1 would not be marked active by folio_set_active(), potentially causing a cold/hot inversion. Besides this issue, the old approach also differs from the current behavior, where we can scan fewer than two generations. Now that we can scan younger generations, including the youngest generation, this no longer prevents rejected folios from being placed in a generation below or at the populated generation. Such rejected folios would then be scanned again and again, resulting in extremely low `pg_steal/pg_scan` ratios. For example: pgsteal_file: 2312605 pgscan_file: 36465693 reclamation efficiency: 6.34% We pass `scanned_seq` to `move_folios_to_lru()` and make sure we either promote the folio or place it in the youngest generation when the populated generation is already the youngest one. Also, folio_set_active() is no longer needed. With this change, the results become: pgsteal_file: 2683815 pgscan_file: 4224244 reclamation efficiency: 63.53% The sys time for building the kernel also decreased from 4m30.532s to 3m50.188s while swappiness==1. Signed-off-by: Barry Song (Xiaomi) Reviewed-by: Kunwu Chan --- include/linux/mm_inline.h | 22 +++++++++++++++++++++- mm/vmscan.c | 24 ++++++++++++------------ 2 files changed, 33 insertions(+), 13 deletions(-) diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index ab69b9930893..f6f4bc9a704f 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 struct lruvec *lruvec, return max(READ_ONCE(lrugen->max_seq) - gen + 1, READ_ONCE(lrugen->min_seq[type])); } -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 folio *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 *lruvec, struct folio *folio, return false; seq = lru_gen_folio_seq(lruvec, folio, reclaiming); + if (scanned_seq != -1UL) + seq = max(seq, min(scanned_seq + 1, lrugen->max_seq)); gen = lru_gen_from_seq(seq); flags = (gen + 1UL) << LRU_GEN_PGOFF; /* see the comment on MIN_NR_GENS about PG_active */ @@ -362,6 +365,17 @@ static inline bool lru_gen_add_folio(struct lruvec *lruvec, struct folio *folio, return true; } +static inline bool lru_gen_add_folio(struct lruvec *lruvec, struct folio *folio, bool reclaiming) +{ + return __lru_gen_add_folio(lruvec, folio, -1UL, reclaiming); +} + +static inline bool lru_gen_add_rejected_folio(struct lruvec *lruvec, struct folio *folio, + unsigned long scanned_seq) +{ + return __lru_gen_add_folio(lruvec, folio, scanned_seq, false); +} + static inline bool lru_gen_del_folio(struct lruvec *lruvec, struct folio *folio, bool reclaiming) { unsigned long flags; @@ -420,6 +434,12 @@ static inline bool lru_gen_add_folio(struct lruvec *lruvec, struct folio *folio, return false; } +static inline bool lru_gen_add_rejected_folio(struct lruvec *lruvec, struct folio *folio, + unsigned long scanned_seq) +{ + return false; +} + static inline bool lru_gen_del_folio(struct lruvec *lruvec, struct folio *folio, bool reclaiming) { return false; diff --git a/mm/vmscan.c b/mm/vmscan.c index 8e0972db35da..8bdc88748959 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1865,7 +1865,8 @@ static bool too_many_isolated(struct pglist_data *pgdat, int file, * * Note: The caller must not hold any lruvec lock. */ -static unsigned int move_folios_to_lru(struct list_head *list, bool do_rotate) +static unsigned int move_folios_to_lru(struct list_head *list, unsigned long seq, + bool do_rotate) { int nr_pages, nr_moved = 0; struct lruvec *lruvec = NULL; @@ -1922,7 +1923,7 @@ static unsigned int move_folios_to_lru(struct list_head *list, bool do_rotate) !folio_test_referenced(folio) && folio_ref_count(folio) == folio_expected_ref_count(folio)) lruvec_add_folio_tail(lruvec, folio); - else + else if (seq == -1UL || !lru_gen_add_rejected_folio(lruvec, folio, seq)) lruvec_add_folio(lruvec, folio); nr_pages = folio_nr_pages(folio); @@ -2041,7 +2042,7 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan, nr_reclaimed = shrink_folio_list(&folio_list, pgdat, sc, &stat, false, lruvec_memcg(lruvec)); - move_folios_to_lru(&folio_list, true); + move_folios_to_lru(&folio_list, -1UL, true); mod_lruvec_state(lruvec, PGDEMOTE_KSWAPD + reclaimer_offset(sc), stat.nr_demoted); @@ -2152,8 +2153,8 @@ static void shrink_active_list(unsigned long nr_to_scan, /* * Move folios back to the lru list. */ - nr_activate = move_folios_to_lru(&l_active, false); - nr_deactivate = move_folios_to_lru(&l_inactive, false); + nr_activate = move_folios_to_lru(&l_active, -1UL, false); + nr_deactivate = move_folios_to_lru(&l_inactive, -1UL, false); count_vm_events(PGDEACTIVATE, nr_deactivate); count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate); @@ -4753,7 +4754,8 @@ static bool isolate_folio(struct lruvec *lruvec, struct folio *folio, struct sca 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) + struct list_head *list, int *isolatedp, + unsigned long *scanned_seq) { enum node_stat_item item; int zone_idx; @@ -4784,6 +4786,7 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec, seq = lrugen->max_seq; seq = lruvec_populated_min_seq(lruvec, type, sc->reclaim_idx + 1, seq); + *scanned_seq = seq; gen = lru_gen_from_seq(seq); max_gen = lru_gen_from_seq(max_seq); @@ -4980,6 +4983,7 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec, int tier, scanned, reclaimed; int isolated = 0, nr_isolated = 0; unsigned long total_reclaimed = 0; + unsigned long scanned_seq; bool skip_retry = false; struct mem_cgroup *memcg = lruvec_memcg(lruvec); struct pglist_data *pgdat = lruvec_pgdat(lruvec); @@ -4991,7 +4995,7 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec, tier = get_tier_idx(lruvec, type); scanned = scan_folios(nr_to_scan, lruvec, sc, - type, tier, &list, &isolated); + type, tier, &list, &isolated, &scanned_seq); nr_isolated = isolated; if (nr_isolated) __mod_node_page_state(pgdat, NR_ISOLATED_ANON + type, @@ -5017,8 +5021,6 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec, type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON); list_for_each_entry_safe_reverse(folio, next, &list, lru) { - DEFINE_MIN_SEQ(lruvec); - /* move_folios_to_lru() culls unevictable folios via folio_putback_lru() */ if (!folio_evictable(folio)) continue; @@ -5037,11 +5039,9 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec, * so this effectively promotes them by at least one generation. */ folio_set_lru_refs(folio, 0); - if (lru_gen_folio_seq(lruvec, folio, false) == min_seq[type]) - folio_set_active(folio); } - move_folios_to_lru(&list, false); + move_folios_to_lru(&list, scanned_seq, false); walk = current->reclaim_state->mm_walk; if (walk && walk->batched) { -- 2.39.3 (Apple Git-146)