From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f177.google.com (mail-pl1-f177.google.com [209.85.214.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7739C277C96 for ; Sun, 30 Aug 2026 03:59:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788062342; cv=none; b=kZWyltwoAFqyNEyQjfBpy4D53W/bICko20UDA906pEHQEQ3GrpLjqx8ejwBYoTQ+xd+3zTEp+J5uf7vq7bhuWCCsSOMgDL82vxiCaaT7XRKBiux+/pZA09IMACSI/oTw8qKUIf9seGxcOzI90H+fmmbtnEnzeBrvjFsP+3po658= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788062342; c=relaxed/simple; bh=qxAWLvKfdMNs+qMSByaRxvFcV3DKRTohVFWladS/eg8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=QUZgQJ8hYswcsuR/aqS4E9Qmr6qj9g7/XVVbrnQTpfKBcgOSZk5SuoxRRy7U/oXr3QoG3q23lkj/u/EXA4QLzQtVUhuTZ9zLGtRWmu0213DaFZpJFMblgQO9fpsO+iuLNZK+EGAOuQG5XSpq3TFxWwcbAhkSmutnmhQ+OSh8Lro= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=PR4rsqtV; arc=none smtp.client-ip=209.85.214.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="PR4rsqtV" Received: by mail-pl1-f177.google.com with SMTP id d9443c01a7336-2d58efc7356so27188675ad.1 for ; Sat, 29 Aug 2026 20:59:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1788062341; x=1788667141; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=mQ8dbbiBgPJ6FDZbDcbGb0ykdxb6d7xQ7LY+xp+A1UQ=; b=PR4rsqtVjkeQJkzkCqB1NimaORo0z/qGbb67Y1V6GWoNqeS2O7H1ZLcGjTZqxT3Ua2 oBByrCguOIKlrhX5rtcU2KVbGmzd8nCq7VXBC+yyofjbxmoELpYiaUFk62etXSziZvf7 ZTH99qIYez9hDPPnVRYmZiQjlTwJf+5PaGYtJodGUYNj6lcFS0BRlMBzliZsWcUZKQ0D zkasTG6p9ppil3Ax8RDjeCJWr/1Y2BanRwBo2VFVksaJvZpec1uLB3nOgG/BDVvLd4Kp mjPKEJYvw71HzS711KMoP3bhLIfKtSKItf58FZRvUVTVtvCXWJ0o+snoX8hzy8EBFbJB MtcQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788062341; x=1788667141; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=mQ8dbbiBgPJ6FDZbDcbGb0ykdxb6d7xQ7LY+xp+A1UQ=; b=pcZp00Mq0ft7Gpo9g9S+8/PAh7Kt7AKcC+E9iuYwFB3y1oggc0wf/QnBDB7nMzw3GS J3nWkRxSmvuIH017HuBlXHINE7oLx4/SVSfFJcFPawDU82n+vYOic3iGDdsym4ZhgD1P y0apM4AStqg8Jgfqny8M2zkEkrattGBM4zexxPWXOnnQ3xAl3DqA2QQLvxDonUJCQ2bm k8dcDTrsC4mWfGscDIPhmkwV2jV6nLrUX1aa7Ak7wRAwBnbTSbYdwXp1MtIBTrMgWf4n 7lW+CvnSd3Wm/oFOuuDc0JXpgZgh9UKSaMx+TlnP8bh2Y1QKkW8sSMANIjwcOOnpRnzJ wKOg== X-Forwarded-Encrypted: i=1; AHgh+RqltesjCaYv03atQR+QIScOt0qfAsJOPDAZ+FDqV9H7MMyNUpvtFbwo1J7ArdMzsZY5v5TMrgOtI0zPmF4=@vger.kernel.org X-Gm-Message-State: AFuF++nhxcZtxZGNDM/8BJRidjybpFIkxuiivkSZbg1h0tfnKMLoNMJB 2pkq9z0BFQUduFMWuE5gshR42+rZPINLACu4kybfHpG6ek4lhlBULQcN X-Gm-Gg: AYBFou0VYjkToIARA6v7zeYQa9O9NaHMNxZiIWGSeWJsRJg1Iv7IRVUg8RprvigZLHZ k8fFm+p4aPhyCyS6Y6vDlaspFuI2J456VhA/MCl+eifMrzHc1Tf1NQxkZ4i/a9Na+N6V7RhI3ao yUIDOx3yLEBJQ3qKTCmInAQoNoiSXR/UKYPQ9S7JYvCEXJBgNdOiZpwctW+GgAiV7eKJByjKBUw saaWTkEhr7ZYkYDHazUCcTrPJGifb/DlI3UsdmX4CMVjwKCu9IDhgNYULHZ6ffDkPLmrQzXwgYh NcoQZW9SNIQp420tRvVoSAy8dLnROfjQYz5wYZTldFkkf3hDQW6Cg+RsmOs+O3LxAFqJui1KD+E I75qpUilpnlr2K3Q3x0R76fReqYWW/sxKH73B0WRG1jB2YWp7vll44jkgrZ4dgtVHCRS+b5/CKE fOjG+Dna6AXku8cveD4KMtL1vw3kem5D5hJO+k9ZanKnubIQ2OQBZCw5Rm1BGU X-Received: by 2002:a17:902:f78b:b0:2c9:df1b:e948 with SMTP id d9443c01a7336-2d74dc78debmr295950455ad.4.1788062340334; Sat, 29 Aug 2026 20:59:00 -0700 (PDT) Received: from gmail.com ([185.220.238.38]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2d75988d184sm18386975ad.62.2026.08.29.20.58.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 29 Aug 2026 20:58:59 -0700 (PDT) From: Kunwu Chan X-Google-Original-From: Kunwu Chan To: "Barry Song (Xiaomi)" Cc: Kunwu Chan , akpm@linux-foundation.org, lianux.mm@gmail.com, axelrasmussen@google.com, baolin.wang@linux.alibaba.com, baoquan.he@linux.dev, chenridong@xiaomi.com, david@kernel.org, hannes@cmpxchg.org, kasong@tencent.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, lyugaofei@xiaomi.com, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, stevensd@chromium.org, wangzicheng@honor.com, weixugc@google.com, yuanchu@google.com, zhangbo56@xiaomi.com, Xueyuan Chen Subject: Re: [PATCH v2 2/7] mm/mglru: batch update lrugen->nr_pages in inc_min_seq() Date: Sun, 30 Aug 2026 11:58:38 +0800 Message-ID: <20260830035843.712320-1-kunwu.chan@linux.dev> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260827234704.63163-3-baohua@kernel.org> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Fri, 28 Aug 2026 07:46:59 +0800 "Barry Song (Xiaomi)" wrote: > Currently, folio_inc_gen() updates lrugen->nr_pages for every folio > as it advances generations. Instead, accumulate the size changes > and update lrugen->nr_pages in a batch after scanning the entire > oldest generation, or when the scan stops because remaining reaches > zero. > > Since we only move folios from the oldest generation to the second > oldest generation, the active/inactive state cannot change. We can > therefore skip __lru_update_size(). > > Signed-off-by: Barry Song (Xiaomi) > Tested-by: Xueyuan Chen > --- > mm/vmscan.c | 23 ++++++++++++++++++----- > 1 file changed, 18 insertions(+), 5 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 8f187d296b8e..07c22d51debd 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3918,6 +3918,7 @@ static bool inc_min_seq(struct lruvec *lruvec, int type, int swappiness) > struct lru_gen_folio *lrugen = &lruvec->lrugen; > int hist = lru_hist_from_seq(lrugen->min_seq[type]); > int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); > + int target_gen = (old_gen + 1) % MAX_NR_GENS; > > /* For file type, skip the check if swappiness is anon only */ > if (type && (swappiness == SWAPPINESS_ANON_ONLY)) > @@ -3927,35 +3928,47 @@ static bool inc_min_seq(struct lruvec *lruvec, int type, int swappiness) > if (!type && !swappiness) > goto done; > > + VM_WARN_ON_ONCE(get_nr_gens(lruvec, type) != MAX_NR_GENS); > + VM_WARN_ON_ONCE(lru_gen_is_active(lruvec, old_gen) != > + lru_gen_is_active(lruvec, target_gen)); > /* prevent cold/hot inversion if the type is evictable */ > for (zone = 0; zone < MAX_NR_ZONES; zone++) { > struct list_head *head = &lrugen->folios[old_gen][type][zone]; > + long delta = 0; > > while (!list_empty(head)) { > struct folio *folio = lru_to_folio(head); > + long nr_pages = folio_nr_pages(folio); > int refs = folio_lru_refs(folio); > bool workingset = folio_test_workingset(folio); > + bool gen_increased; > > 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); > > - new_gen = folio_inc_gen(lruvec, folio); > + new_gen = __folio_inc_gen(folio, old_gen, &gen_increased); > list_move_tail(&folio->lru, &lrugen->folios[new_gen][type][zone]); > - > + if (gen_increased) > + delta += nr_pages; > /* don't count the workingset being lazily promoted */ > if (refs + workingset != BIT(LRU_REFS_WIDTH) + 1) { > int tier = lru_tier_from_refs(refs, workingset); > - int delta = folio_nr_pages(folio); > > WRITE_ONCE(lrugen->protected[hist][type][tier], > - lrugen->protected[hist][type][tier] + delta); > + lrugen->protected[hist][type][tier] + nr_pages); > } > > if (!--remaining) > - return false; > + break; > } > + WRITE_ONCE(lrugen->nr_pages[old_gen][type][zone], > + lrugen->nr_pages[old_gen][type][zone] - delta); > + WRITE_ONCE(lrugen->nr_pages[target_gen][type][zone], > + lrugen->nr_pages[target_gen][type][zone] + delta); Hi Barry, One subtle point about the `remaining` handling: when `remaining` reaches zero, we now `break` rather than return so that the accumulated `delta` is applied before returning. As I understand it, this is required because `__folio_inc_gen()` has already changed the generation of the scanned folios, while `lrugen->nr_pages[]` is now updated only in batch. So the invariant is that every successful generation increment must have its corresponding `delta` flushed before `inc_min_seq()` returns. Is this the intended accounting invariant? Thanks, KunWu > + if (!remaining) > + return false; > } > done: > reset_ctrl_pos(lruvec, type, true); > -- > 2.34.1 > >