From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.128.172 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793222499; b=L1a3huBxeSvnqwS7+KnYSQrF3h0680enafaVAKjIx2c1aUaXz1U2x2MUG0w82KM8bHrV dpcn2okYpinphU8izsLwMDMEDtlTKuPt+qCZeX6Rre91r8nPUDUMLPnCHN6esRQHidgfH ZrtAPCFy0o0HZH+d+hNbzIgmZz+gG2DRY4SUHDFUp1Tbw7l317BNucQky8KafOX0ojv4Y 1H2u20oIzys83sdwpseiF/NFk/hdnjSijXCnAhyY5aHbz2UQQtm7uWtDUVCt/EERomA87 uk0izH+npnUtVziOSj0lV9MTUZc0ySE6aSQpuIq8CTm0stIVLUQfRLslgnkxnjBAURw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793222499; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; bh=/AnoOf4KaoFS/ftZh5xPkws/q1U7dINbhxvKXiKw/hw=; b=G1OLO/xOey+Aoikpla61AdFXZMnW76uQ6hJ+YeROt+H8tpJ+9eJ6jBJioiyofj1mpQnb Tp64uMK0g6LoEdszbxeBfJ7WlIQrcRKwBXT/kC0CQnTtMj4IykolWfLlkwO4N776ZEKQO whaMy6db/9z9abfSC4anTuowMgrw0IAdtgIjukx2qCirfLK0yfnIvpB+FnL61kgRvinIn qvgz+nTzPWcNk4dQQLCges/mOOOFLnn8vOh0sTOqQcteQ/OMV3Q8+8U5oH7zErqvkHZSS w0R0rZBnnj6g+/XO3rorqpvLrml7BGCKXuBXp1gNyUZd4h8ALZdhlH0UUH29ZdQeIWQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=cmpxchg.org; spf=pass smtp.mailfrom=cmpxchg.org; dkim=pass header.d=cmpxchg.org header.i=@cmpxchg.org header.a=rsa-sha256 header.s=google header.b=C0bh0Mps; arc=none smtp.remote-ip=209.85.128.172 Received: from mail-yw1-f172.google.com (mail-yw1-f172.google.com [209.85.128.172]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 606E2606A31E for ; Wed, 28 Oct 2026 21:21:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 606E2606A31E Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=cmpxchg.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=cmpxchg.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=cmpxchg.org header.i=@cmpxchg.org header.a=rsa-sha256 header.s=google header.b=C0bh0Mps Received: by mail-yw1-f172.google.com with SMTP id 00721157ae682-8565d77c277so13599557b3.0 for ; Wed, 28 Oct 2026 14:21:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg.org; s=google; t=1793222497; x=1793827297; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=/AnoOf4KaoFS/ftZh5xPkws/q1U7dINbhxvKXiKw/hw=; b=C0bh0Mps1qm3/4kL6QqtrrocFRbdkoL6IZA3D82P0RWdr6+DOFzB8s5zW2RI8bVS2K Mg27GpCHXxtvNQpZkQ0yZmqL/72TEG7KSkRWdsmZIEDDitYmUvSx9qCSpt7OmPUv0Y4s r2eJBY/DmmL83xCy2P/sXRSP3APelzWGeej4J2Zq6ph5V+QNpKYwLpne/F0khHpkREjs A3dl30zWrM9zQQ0sgMSDVF2yky9YFY/9QsrLalMQrbn2vK8EI1R0TRsnqvdKtp7PnFXi zDCm02U7MnGPnYpz6QunJCDJikTzZWC2QMuYth2M8sI99Y/BW+ITdq+6HiGu7BxdsEwN 8sFg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793222497; x=1793827297; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=/AnoOf4KaoFS/ftZh5xPkws/q1U7dINbhxvKXiKw/hw=; b=z5sKBV42gTILK8eQbLeKNSwd0Bn9JK9huEOC0oGKn2yg9sR6eWTSdrb86KygRCwfZ3 TquI78H+YzzYPIblVwi31+un8ylj/RdiQEL2qszZMrOenftdBllB8jBABzIGyc8s3wUd fiSW/ar6Qf/xME2dqCJYgQHHsPgrWwWKEOug34AlnKrdwzbfyXajbZ1bBeYEnggEECRl T1xApKWGuMNRs6br6rdLDkjD7GHB1GXYypZ6Wgh1Q/l9tzFWMON5AtmSR5CtPoS0Mk+v 9fE4ztcPWEdCYPHFswVS15mlciRkhHbH3NJWC90N5VAxfEfdt7vfN9Xu++breopLYGKQ CaGQ== X-Forwarded-Encrypted: i=1; AKwUvBwxf+0Mp8Krz80Nb31sVg+HZQDprKlw7yG/q3vZ6dDaCrWDQM2Abd2zFxPkaOw4xe2tECxcf77S/a8y0yY=@vger.kernel.org X-Gm-Message-State: AFq9FYJRSUO4iopEwleHhpT/0wkZajmNrhtZtt/eV13tZfiGfV7zEmLG z8T1tR5u0JkmHwqjcQvIIOwLcS7lmYakGqgKUdZM98EgBwGF026NXbZwKZZIUB3Yp0g= X-Gm-Gg: AYBFou03oEQOD0HnCWdRLeq3APoMSwPUtBuOKZ9nbpDkvxKQ46Ux0XZ+9xSzYLt3H0A /MJi4ZMuEsVz0waPJ3oT2EhkMIMbWHtjInlSf8znZNNhisIilZEWcSceIXWUxK58RVxFviHHX5p hXLDCoS5b33bgM96B9sOSP6S9loxW3USC8EywhKl7O9hLwaidxpaCbIePRC0NCJVyLVwIE6vzMg 5UlD7WIsfS7TUoYuiI4MGdURsSVnKrALNnN5S7O5m7CKfEpb58nR1gmiM+nZPcI0kNHOE8ya9MI MCLmWTw1q/7W8im2vDAAeZgJtsm/XHqGRobV+eHTQnKDzodhE0MXFximg7f2dBp4wEpNjvvDPLy IFsZl1jLwQpWuK54f7rE8UakvnaUNsGiZTZ4OQicq5Eau7+oHNzh6ptxRFv57Yb4i+1KHdAxKRo ZAzqeayOwDGO/GrceNH1iNgK6IoYIxZanzsR1plOSOczDvYbXfD7rKLlIRfekkDOJZjexb12jQq Hc6glhAdQns1dQnMDgnQTbHLzGgh6ZFVdTjQdWfm3W08U8m1Fuj63XpHHe0LGIAe/OOmUxqF8Th TLkd+8ie/I6zMwTIYEdaULt43rw3 X-Received: by 2002:a05:690c:c5e0:b0:8a6:1901:30d9 with SMTP id 00721157ae682-8b1b5c9952emr18568837b3.37.1793222497186; Wed, 28 Oct 2026 14:21:37 -0700 (PDT) Received: from localhost ([2605:8600:200:14e3:365a:60ff:fe62:ff29]) by smtp.gmail.com with ESMTPSA id 00721157ae682-8b19e566718sm35368027b3.17.2026.10.28.14.21.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Oct 2026 14:21:36 -0700 (PDT) Date: Wed, 28 Oct 2026 17:21:36 -0400 From: Johannes Weiner To: "T.J. Mercier" Cc: roman.gushchin@linux.dev, muchun.song@linux.dev, Andrew Morton , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm/vmscan: remove redundant !mem_cgroup_online() checks Message-ID: References: <20261028010611.3929937-1-tjmercier@google.com> <20261028010611.3929937-2-tjmercier@google.com> 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-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261028010611.3929937-2-tjmercier@google.com> On Tue, Oct 27, 2026 at 06:06:05PM -0700, T.J. Mercier wrote: > Since commit f1cf8d2f36dc ("mm: memcontrol: eliminate the problem of > dying memory cgroup for LRU folios") and commit 0e0ac326c511 ("memcg: > move LRU size accounting on reparenting instead of copying it"), > mem_cgroup_css_offline() reparents all LRU folios to the parent memcg > and zeroes the child's lrugen->nr_pages and lru_zone_size before the > memcg is offlined. Nothing can repopulate the offlined memcg's lruvec > afterwards. A folio that is off the LRU during reparenting looks up its > lruvec through its objcg, which now points to the parent so it is put > back on the parent's LRU. > > As a result, lruvec_lru_size() and lruvec_evictable_size() are always 0 > when !mem_cgroup_online(memcg) is true, making the offlined memcg special > cases in get_scan_count(), lruvec_is_sizable(), and shrink_one() dead > code. Remove them. > > With the get_nr_to_scan() special case removed, an offlined memcg that > still has stale effective protection now has > apply_proportional_protection() applied like get_scan_count() does, so > the MGLRU and traditional LRU behavior is now the same. > > Signed-off-by: T.J. Mercier Great cleanup! Reviewed-by: Johannes Weiner