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 7FA9CC433EF for ; Thu, 3 Feb 2022 09:08:36 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E0A188D0134; Thu, 3 Feb 2022 04:08:35 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id DB9B68D0129; Thu, 3 Feb 2022 04:08:35 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CA8D28D0134; Thu, 3 Feb 2022 04:08:35 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0037.hostedemail.com [216.40.44.37]) by kanga.kvack.org (Postfix) with ESMTP id BA8AC8D0129 for ; Thu, 3 Feb 2022 04:08:35 -0500 (EST) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 7E325824C420 for ; Thu, 3 Feb 2022 09:08:35 +0000 (UTC) X-FDA: 79100892990.17.E37F1B4 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf17.hostedemail.com (Postfix) with ESMTP id 037CC40002 for ; Thu, 3 Feb 2022 09:08:34 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 00573B8337D; Thu, 3 Feb 2022 09:08:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EDA74C340E4; Thu, 3 Feb 2022 09:08:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1643879311; bh=7u/Bs8VCx4btJL0Iv7cVy8hwmI7nfPr4cRnwbYwSL1w=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nWitOjGfK5MlF1u/cRR+9uRjHe8k1vJaSwWkHHfhHJdJYZKvoFMxD32y6L9uFrp+i gq6STFgJWTgpISfgjEPChY0QTU0Z3MG9WHOQu4QcNALFgRHBjOCCoLLkVyXiUa57Vc nJKtnNzelz72takioqplgT4b+aiTCkTN8Hzk5IoDVQH6TFNZW1x3U30VTX7acv77xf 0S+AsPaM9CUFdhqziI1j/+CGMrOwGbqDz/QwbywasJ3AFU8JiHC4olx1YJ0ko9ToRe pTKHj0MElslO+/0BUBWd3+dptYWhwPwD0ttJgDeyTVG3kGVmxujJlx5ZPyYYdtry97 OGCs/Ss0lhktw== Date: Thu, 3 Feb 2022 11:08:22 +0200 From: Mike Rapoport To: David Hildenbrand Cc: Wei Yang , Michal Hocko , Andrew Morton , linux-mm@kvack.org, LKML , Alexey Makhalov , Dennis Zhou , Eric Dumazet , Oscar Salvador , Tejun Heo , Christoph Lameter , Nico Pache , Rafael Aquini Subject: Re: [PATCH 2/6] mm: handle uninitialized numa nodes gracefully Message-ID: References: <20220127085305.20890-1-mhocko@kernel.org> <20220127085305.20890-3-mhocko@kernel.org> <20220201024119.2ailcw4rp5thambz@master> <20220203002116.akpk5um5nkpeflve@master> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 037CC40002 X-Stat-Signature: 1gcttz71pf9srjbtcknfb4jafy7dyhh8 X-Rspam-User: nil Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=nWitOjGf; spf=pass (imf17.hostedemail.com: domain of rppt@kernel.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=none) header.from=kernel.org X-HE-Tag: 1643879314-953893 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Feb 03, 2022 at 09:27:16AM +0100, David Hildenbrand wrote: > On 03.02.22 08:23, Mike Rapoport wrote: > > On Thu, Feb 03, 2022 at 12:21:16AM +0000, Wei Yang wrote: > >> On Tue, Feb 01, 2022 at 10:54:37AM +0100, Michal Hocko wrote: > >>> On Tue 01-02-22 02:41:19, Wei Yang wrote: > >>>> On Thu, Jan 27, 2022 at 03:47:40PM +0100, Michal Hocko wrote: > >>>> [...] > >>>>>>> + /* > >>>>>>> + * not marking this node online because we do not want to > >>>>>>> + * confuse userspace by sysfs files/directories for node > >>>>>>> + * without any memory attached to it (see topology_init) > >>>>>>> + * The pgdat will get fully initialized when a memory is > >>>>>>> + * hotpluged into it by hotadd_init_pgdat > >>>>>>> + */ > >>>> > >>>> Hmm... which following step would mark the node online? On x86, the node is > >>>> onlined in alloc_node_date(). This is not onlined here. > >>> > >>> The comment tries to explain that this happens during the memory > >>> hotplug. Or maybe I have missed your question? > >>> > >> > >> I am not sure for others, while the comment confused me a little. > >> > >> Currently in kernel, there are two situations for node online: > >> > >> * during memory hotplug > >> * during sys-init > >> > >> For memory hotplug, we allocate pgdat and online node. And current hot-add > >> process has already put them in two steps: > >> > >> 1. __try_online_node() > >> 2. node_set_online() > >> > >> So emphasize "not online" node here, confuse me a little. It is a natural > >> thing to not online node until it has memory. > >> > >> But from another point of view, the comment here is reasonable. During > >> sys-init, we online node at the same time when creating pgdat. And even for > >> memory-less node on x86, we online them too. > >> > >> Well, this is all about the comment. I have tried to grab may head but not > >> come up with a better idea. > >> > >> Or maybe this is just my personal feeling, don't bother if no-one else feel > >> like this. > > > > I shuffled the words a bit, maybe this sounds better not only to me :) > > > > /* > > * We do not want to confuse userspace by sysfs files/directories for node > > * without any memory attached to it, so this node is not marked as > > * N_MEMORY and not marked online so that topology_init() won't create > > * sysfs hierarchy for this node. The pgdat will get fully initialized by > > * hotadd_init_pgdat() when memory is hotpluged into this node > > */ > > > > Note that the topology_init() part might change soon [1] so maybe we > want to rephrase that to "so that no sysfs hierarchy will be created via > register_one_node() for this node." right away. Heh, this will be your responsibility to update the comment here when you post non-RFC version ;-) > or (because there is also /sys/devices/system/node/online ) > > "so that the node won't be indicated as online to user space, for > example, via register_one_node()." > > [1] https://lkml.kernel.org/r/20220128151540.164759-1-david@redhat.com > > -- > Thanks, > > David / dhildenb > -- Sincerely yours, Mike.