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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D072CC433F5 for ; Tue, 14 Dec 2021 10:38:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233097AbhLNKit (ORCPT ); Tue, 14 Dec 2021 05:38:49 -0500 Received: from smtp-out2.suse.de ([195.135.220.29]:35962 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231272AbhLNKis (ORCPT ); Tue, 14 Dec 2021 05:38:48 -0500 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id F3D571F3C3; Tue, 14 Dec 2021 10:38:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1639478328; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=i6n+Du2Wanh5ToBgLy61lXqvAYk0Hql+XD6WjB+onmA=; b=UgpMzDjzqvaqK2eA8pYmdzyJA0o5cKaOXihZC1qXCviolEqlmHU9K2C33kzegRjwuBL3Xl Y5K0fR/h2rCZugKxiVIFnQbPMU0w6JNSKurue3ZFBaIQmrQHvuttIhV4gspgj2iPsXdWne aaB+Ik7drz9CSfkPopO6Y9n0TJGPelo= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id BAD29A3B84; Tue, 14 Dec 2021 10:38:47 +0000 (UTC) Date: Tue, 14 Dec 2021 11:38:47 +0100 From: Michal Hocko To: Christoph Lameter Cc: Andrew Morton , David Hildenbrand , Alexey Makhalov , LKML , linux-mm@kvack.org, Dennis Zhou , Eric Dumazet , Oscar Salvador , Tejun Heo , Nico Pache Subject: Re: [PATCH v2 2/4] mm: handle uninitialized numa nodes gracefully Message-ID: References: <20211214100732.26335-1-mhocko@kernel.org> <20211214100732.26335-3-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 14-12-21 11:33:41, Christoph Lameter wrote: > On Tue, 14 Dec 2021, Michal Hocko wrote: > > > This patch takes a different approach (following a lead of [3]) and it > > pre allocates pgdat for all possible nodes in an arch indipendent code > > - free_area_init. All uninitialized nodes are treated as memoryless > > nodes. node_state of the node is not changed because that would lead to > > other side effects - e.g. sysfs representation of such a node and from > > past discussions [4] it is known that some tools might have problems > > digesting that. > > Would it be possible to define a pgdat statically and place it in read > only memory? Populate with values that ensure that the page allocator > does not blow up but does a defined fallback. > > Point the pgdat for all nodes not online to that readonly pgdat? > > Maybe that would save some memory. When the node comes online then a real > pgdat could be allocated. This is certainly possible but also it is more complex. I aim for as simple as possible at this stage. The reason I am not concerned about memory overhead so much (even though the pgdat is a large data structure) is that these unpopulated nodes are rather rare. We might see more of them in the future but we are not quite there yet so I do not think this is a major obstacle for now. -- Michal Hocko SUSE Labs