From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4B266C282CD for ; Mon, 3 Mar 2025 16:20:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A61BF6B0083; Mon, 3 Mar 2025 11:19:59 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A1CD46B0085; Mon, 3 Mar 2025 11:19:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8DAB56B0088; Mon, 3 Mar 2025 11:19:59 -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 74B0D6B0083 for ; Mon, 3 Mar 2025 11:19:59 -0500 (EST) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 1394851DAA for ; Mon, 3 Mar 2025 16:19:59 +0000 (UTC) X-FDA: 83180751318.22.5D1693E Received: from mail-qv1-f53.google.com (mail-qv1-f53.google.com [209.85.219.53]) by imf11.hostedemail.com (Postfix) with ESMTP id 34A3B40011 for ; Mon, 3 Mar 2025 16:19:57 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=gourry.net header.s=google header.b=A7oeJd+i; spf=pass (imf11.hostedemail.com: domain of gourry@gourry.net designates 209.85.219.53 as permitted sender) smtp.mailfrom=gourry@gourry.net; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1741018797; 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-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=npU4Q2NKzI8EHqsYS1IQDm8fptT5XAkaolwjBVod8c4=; b=iY1NfPfB24GjSiI/uBhcdHwxoqqe1UOgMhNxAGNwe8uZeERZIfQVNrahkBY/Ym0gkt78U2 RPaLFKUjF4zUVe9oNXbCPtY5XpRrtvIwG4k3jJo2FJ7NfVniuwU0O5nLfK4h+wfjr9e3Ar gWk0CX8rAKt2d8xoG3PDDg3acIooXxQ= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=gourry.net header.s=google header.b=A7oeJd+i; spf=pass (imf11.hostedemail.com: domain of gourry@gourry.net designates 209.85.219.53 as permitted sender) smtp.mailfrom=gourry@gourry.net; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1741018797; a=rsa-sha256; cv=none; b=k82ALecHoqmOrogz6s9waDIOgtLHLKvgl4Bw0dewf/tfkeXtXob8d7Ueqb22Ia5Hb/wPzq uXpDObXmx8hN0ngRI8fMlD0QJ4XWReaRPKpOsmbM6TnKplwgAZsfMmqsVx7Pl3UUTI3kYz 1svq/aJdnk+7z21j0FEWoOUO0N7u2JU= Received: by mail-qv1-f53.google.com with SMTP id 6a1803df08f44-6e89ccbbaa9so31849326d6.2 for ; Mon, 03 Mar 2025 08:19:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gourry.net; s=google; t=1741018796; x=1741623596; darn=kvack.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=npU4Q2NKzI8EHqsYS1IQDm8fptT5XAkaolwjBVod8c4=; b=A7oeJd+i5rXZUyLPREYFg2bCYl6i/T19PCxLgipn+o1IZw5CqGdJz87iZ2IQidHwq4 RL9RLaF6vp+lwPGpjxJXOPWkjFJSJPsz954o50W/Om/67GqjaHwIPDi+iHRZwsEceAmR sLC4xxCeaMpkbU2Ju7o4A9gnVPDwxcac6ogJT5oX1wLYXY2OzPaPD4+ywULA92AWRjBF yCPb6OacIdje2sB13lhJrl34QRjHtfiA6o+5zWtD3oP85V1RRa9jzRNBZNxy7R87tLg/ 8aVFzwybjxS4USuIaEx6UbgyJAaN8135zL/2ima+Lomm4ZTKBbxDQi6gte2W1sMOtHqK Co0Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1741018796; x=1741623596; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=npU4Q2NKzI8EHqsYS1IQDm8fptT5XAkaolwjBVod8c4=; b=rCXEwM5dNPEXiLna1ZkAhYKF16GVX5Z4KIEx3kQXCHZSwaI8SwXxCEp995BDL5Paly ADzT42FgFwOatlw25Jcf/uVV2spJsJ2tsGwcQRLRKT+liO8iXKipbJ/2c/wioDSyIYmy q5y752+rE5IRKUY7UTmQw5LcSDiEEMD6g50ekl1wgSNnkA4I2gDsz/9hFqP3hrzypttm VHtlgD8byNjEQqhjkHW8Ge+CR0sXcucwkdqFHENbYPCsNmDipmO4JLMH+NXINGzZN7Uc wH1n+dJ/RqyUyxllAcvt05UNVcyBC5mbeG8UpdhMnspoizJXqDCUHcG9OO0xPakiQ4Cl nddQ== X-Forwarded-Encrypted: i=1; AJvYcCUIvke8mDgTPf6CLTnjhGRpySSSaHVRmHyljEQSAKBySX2SXHfcx/a3F5wJDJy7qsxBKbsFH1UGiQ==@kvack.org X-Gm-Message-State: AOJu0YwLho6WxQ+OuTOZJGY6Z44HC7I70bxt/u05rZOKB2dpA5JCBZkX 7u970Dnk8ykOJ52EFY78I+KkVaxUcuVj/7xaqusv585am8EuZliou/alooXCUyM= X-Gm-Gg: ASbGncvzU1nJG8TZiX1zp9sukjppVPl2o/RnYdFguN9fO6RXrHSZkMqhVl/F4Tjo2a/ LtftTDRel8ibmDWMLQWb9ZLw8+0G9jL6ZtvYlUCb7dmyHhF/nGDrKilwgboQJQi0uAhtn1te0hJ 3TJbQ7bPyVfMblY7ouU37sU2qxr45uH/Xlge3OvFYYv+DiGNF4LjcJ3uSeh6i1LR3Rk1UxAL07o BBi5CS9D+eeKLYdiZA9lB0IKZAUWZ75XZNTzzzKX6E6rwSLETbHz76jbM3zoave8r3OpaEHLBC0 kmoiinf+Tg6tvIfaKHIyxr2vjl8eyg3RjnDQkncS5/7hVVjiOvnFrUxaGSui9o2dS9mXEfiB4I8 2xHN/xrztzsmfx9m6XQt2EBdn8no= X-Google-Smtp-Source: AGHT+IFrkNQWQ1CiJuDWkCSRKag4xlr1szBO39O50NkgwvocW88WS9f8hGcizY9NgWfP7fb3nWp2Qw== X-Received: by 2002:a0c:c387:0:b0:6e8:adee:2e6a with SMTP id 6a1803df08f44-6e8adee2f29mr134420576d6.36.1741018796194; Mon, 03 Mar 2025 08:19:56 -0800 (PST) Received: from gourry-fedora-PF4VCD3F (pool-173-79-56-208.washdc.fios.verizon.net. [173.79.56.208]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6e8976ec0f8sm54776936d6.120.2025.03.03.08.19.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Mar 2025 08:19:55 -0800 (PST) Date: Mon, 3 Mar 2025 11:19:53 -0500 From: Gregory Price To: Honggyu Kim Cc: Joshua Hahn , harry.yoo@oracle.com, ying.huang@linux.alibaba.com, kernel_team@skhynix.com, gregkh@linuxfoundation.org, rakie.kim@sk.com, akpm@linux-foundation.org, rafael@kernel.org, lenb@kernel.org, dan.j.williams@intel.com, Jonathan.Cameron@huawei.com, dave.jiang@intel.com, horen.chuang@linux.dev, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com, yunjeong.mun@sk.com Subject: Re: [PATCH 2/2 v6] mm/mempolicy: Don't create weight sysfs for memoryless nodes Message-ID: References: <20250226213518.767670-1-joshua.hahnjy@gmail.com> <20250226213518.767670-2-joshua.hahnjy@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: io5wj8hjpqj1xnc6or9s77xp5nw8c7dz X-Rspamd-Queue-Id: 34A3B40011 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1741018797-733792 X-HE-Meta: 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 w1Mq/bdK Lcs/sUpo5w1DE/pXn6D6+CXiimI6qhTfSahUyOu4uHSRgfuROavPHL9UZ84Wb+PXd4kDNltuH1tJvoXmBcESgItNehgJbGukHq2TSb6evuWU9MFo8vTr4iSYZqJ3595hoOMhgf1/21d6yOMRXxEfF1t1jTZm4axLqvYogsM3SacPZEOekmHSY/11Wo4hAcyIZMLDvIPRKWYpHvWcjT74bwGUnRojHyG6lvpeYBr88swvptPWpovtx4kGx8Vs+dnMITut7yEK9u/INyGggbW2o2twdNDjBo301o+KBOgczBfNB516Os+UZU2B/Ti9fhMokKz7lwiSPgE1pFFbiczFC0ZWXNYszx0lI0Ab9QObkIh8zpwuUvY5Kpoku342lo05IxFdtdsKM1zuOYJfgMn8CLldq+w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000130, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Feb 27, 2025 at 11:32:26AM +0900, Honggyu Kim wrote: > > But using N_MEMORY doesn't fix this problem and it hides the entire CXL > memory nodes in our system because the CXL memory isn't detected at this > point of creating node*. Maybe there is some difference when multiple > CXL memory is detected as a single node. > Hm, well, the node is "created" during early boot when ACPI tables are read and the CFMW are discovered - but they aren't necessarily "online" at the time they're created. There is no true concept of a "Hotplug NUMA Node" - as the node must be created at boot time. (tl;dr: N_POSSIBLE will never change). This patch may have been a bit overzealous of us, I forgot to ask whether N_MEMORY is set for nodes created but not onlined at boot. So this is a good observation. It also doesn't help that this may introduce a subtle race condition. If a node exists (N_POSSIBLE) but hasn't been onlined (!N_MEMORY) and bandwidth information is reported - then we store the bandwidth info but don't include the node in the reduction. Then if the node comes online later, we don't re-trigger reduction. Joshua we should just drop this patch for now and work with Honggyu and friends separately on this issue. In the meantime we can stick with N_POSSIBLE. There are more problems in this space - namely how to handle a system whereby 8 CXL nodes are "possible" but the user only configures 2 (as described by Hyonggye here). We will probably need to introduce hotplug/node on/offline callbacks to re-configure weights. ~Gregory