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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0AC66C433EF for ; Wed, 8 Dec 2021 08:34:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240605AbhLHIi1 (ORCPT ); Wed, 8 Dec 2021 03:38:27 -0500 Received: from smtp-out1.suse.de ([195.135.220.28]:45106 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240745AbhLHIiK (ORCPT ); Wed, 8 Dec 2021 03:38:10 -0500 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 1F4B62113D; Wed, 8 Dec 2021 08:34:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1638952478; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VEx7L2uKEFkh7PkDUkqZJdaZbYdaJ5/ADsblq0a2GMY=; b=uOgd7PBGkpRP1E//AO+SzSyrmxpr1SlUwNEu6/JT7mflDPum0fLmNn+fggTDgNyAZvyUii qKlhVqNWsYUDZ2nDAeMqQI/kFgYFwKrRzgGzbEN9cPygn2buHvYtPoeDBaa5zptKHOV6pb cbBd6qiDyjesz14HH1q3NUId0LNJHKo= 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 E4E87A3B85; Wed, 8 Dec 2021 08:34:37 +0000 (UTC) Date: Wed, 8 Dec 2021 09:34:37 +0100 From: Michal Hocko To: David Hildenbrand Cc: Alexey Makhalov , Dennis Zhou , Eric Dumazet , "linux-mm@kvack.org" , Andrew Morton , Oscar Salvador , Tejun Heo , Christoph Lameter , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" Subject: Re: [PATCH v3] mm: fix panic in __alloc_pages Message-ID: References: <2E174230-04F3-4798-86D5-1257859FFAD8@vmware.com> <21539fc8-15a8-1c8c-4a4f-8b85734d2a0e@redhat.com> <78E39A43-D094-4706-B4BD-18C0B18EB2C3@vmware.com> <5a44c44a-141c-363d-c23e-558edc23b9b4@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5a44c44a-141c-363d-c23e-558edc23b9b4@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 08-12-21 09:24:39, David Hildenbrand wrote: > On 08.12.21 09:12, Michal Hocko wrote: > > On Tue 07-12-21 19:03:28, David Hildenbrand wrote: > >> On 07.12.21 18:17, Alexey Makhalov wrote: > >>> > >>> > >>>> On Dec 7, 2021, at 9:13 AM, David Hildenbrand wrote: > >>>> > >>>> On 07.12.21 18:02, Alexey Makhalov wrote: > >>>>> > >>>>> > >>>>>> On Dec 7, 2021, at 8:36 AM, Michal Hocko wrote: > >>>>>> > >>>>>> On Tue 07-12-21 17:27:29, Michal Hocko wrote: > >>>>>> [...] > >>>>>>> So your proposal is to drop set_node_online from the patch and add it as > >>>>>>> a separate one which handles > >>>>>>> - sysfs part (i.e. do not register a node which doesn't span a > >>>>>>> physical address space) > >>>>>>> - hotplug side of (drop the pgd allocation, register node lazily > >>>>>>> when a first memblocks are registered) > >>>>>> > >>>>>> In other words, the first stage > >>>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c > >>>>>> index c5952749ad40..f9024ba09c53 100644 > >>>>>> --- a/mm/page_alloc.c > >>>>>> +++ b/mm/page_alloc.c > >>>>>> @@ -6382,7 +6382,11 @@ static void __build_all_zonelists(void *data) > >>>>>> if (self && !node_online(self->node_id)) { > >>>>>> build_zonelists(self); > >>>>>> } else { > >>>>>> - for_each_online_node(nid) { > >>>>>> + /* > >>>>>> + * All possible nodes have pgdat preallocated > >>>>>> + * free_area_init > >>>>>> + */ > >>>>>> + for_each_node(nid) { > >>>>>> pg_data_t *pgdat = NODE_DATA(nid); > >>>>>> > >>>>>> build_zonelists(pgdat); > >>>>> > >>>>> Will it blow up memory usage for the nodes which might never be onlined? > >>>>> I prefer the idea of init on demand. > >>>>> > >>>>> Even now there is an existing problem. > >>>>> In my experiments, I observed _huge_ memory consumption increase by increasing number > >>>>> of possible numa nodes. I’m going to report it in separate mail thread. > >>>> > >>>> I already raised that PPC might be problematic in that regard. Which > >>>> architecture / setup do you have in mind that can have a lot of possible > >>>> nodes? > >>>> > >>> It is x86_64 VMware VM, not the regular one, but specially configured (1 vCPU per node, > >>> with hot-plug support, 128 possible nodes) > >> > >> I thought the pgdat would be smaller but I just gave it a test: > > > > Yes, pgdat is quite large! Just embeded zones can eat a lot. > > > >> On my system, pgdata_t is 173824 bytes. So 128 nodes would correspond to > >> 21 MiB, which is indeed a lot. I assume it's due to "struct zonelist", > >> which has MAX_ZONES_PER_ZONELIST == (MAX_NUMNODES * MAX_NR_ZONES) zone > >> references ... > > > > This is what pahole tells me > > struct pglist_data { > > struct zone node_zones[4] __attribute__((__aligned__(64))); /* 0 5632 */ > > /* --- cacheline 88 boundary (5632 bytes) --- */ > > struct zonelist node_zonelists[1]; /* 5632 80 */ > > [...] > > /* size: 6400, cachelines: 100, members: 27 */ > > /* sum members: 6369, holes: 5, sum holes: 31 */ > > > > with my particular config (which is !NUMA). I haven't really checked > > whether there are other places which might scale with MAX_NUM_NODES or > > something like that. > > > > Anyway, is 21MB of wasted space for 128 Node machine something really > > note worthy? > > > > I think we'll soon might see setups (again, CXL is an example, but als > owhen providing a dynamic amount of performance differentiated memory > via virtio-mem) where this will most probably matter. With performance > differentiated memory we'll see a lot more nodes getting used in > general, and a lot more nodes eventually getting hotplugged. There are certainly machines with many nodes. E.g. SLES kernels are build with CONFIG_NODES_SHIFT=10 which is a lot of potential nodes. And I have seen really large machines with many nodes but those usually come with a lot of memory and they do not tend to have non populated nodes AFAIR. > If 128 nodes is realistic, I cannot tell. > > We could optimize by allocating some members dynamically. For example > we'll never need MAX_NUMNODES entries, but only the number of possible > nodes. Yes agreed. Scaling with MAX_NUMNODES is almost always wasteful. -- Michal Hocko SUSE Labs