linux-kernel - Re: [PATCH 2/6] mm: handle uninitialized numa nodes gracefully

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Date:   Tue, 1 Feb 2022 10:54:37 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Wei Yang <richard.weiyang@...il.com>
Cc:     Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        David Hildenbrand <david@...hat.com>,
        Alexey Makhalov <amakhalov@...are.com>,
        Dennis Zhou <dennis@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Oscar Salvador <osalvador@...e.de>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Nico Pache <npache@...hat.com>,
        Rafael Aquini <raquini@...hat.com>
Subject: Re: [PATCH 2/6] mm: handle uninitialized numa nodes gracefully

On Tue 01-02-22 02:41:19, Wei Yang wrote:
> On Thu, Jan 27, 2022 at 03:47:40PM +0100, Michal Hocko wrote:
> >[...]
> >> > +
> >> > +			/* Allocator not initialized yet */
> >> > +			pgdat = arch_alloc_nodedata(nid);
> >> > +			if (!pgdat) {
> >> > +				pr_err("Cannot allocate %zuB for node %d.\n",
> >> > +						sizeof(*pgdat), nid);
> >> > +				continue;
> >> > +			}
> >> > +			arch_refresh_nodedata(nid, pgdat);
> >> > +			free_area_init_memoryless_node(nid);
> 
> free_area_init_memoryless_node() seems to be defined used out side
> page_alloc.c? It just call free_area_init_node() directly. We want to use the
> name to reflect the effect?

yes.

> >> > +			/*
> >> > +			 * 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?

[...]
-- 
Michal Hocko
SUSE Labs