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

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Date:   Tue, 1 Feb 2022 02:41:19 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     Michal Hocko <mhocko@...e.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>,
        Wei Yang <richard.weiyang@...il.com>,
        Rafael Aquini <raquini@...hat.com>
Subject: Re: [PATCH 2/6] mm: handle uninitialized numa nodes gracefully

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?

>> > +			/*
>> > +			 * 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.

>> > +			continue;
>> 
>> This can be made slightly more concise if we fall through after
>> arch_refresh_nodedata(), e.g. something like
>> 
>> 			...
>> 
>> 			arch_refresh_nodedata(nid, pgdat);
>> 		}
>> 
>> 		pgdat = NODE_DATA(nid);
>> 		free_area_init_node(nid);
>> 
>> 		/*
>> 		 * Do not mark memoryless 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
>> 		 */
>> 		if (!pgdat->node_present_pages)
>> 			continue;
>> 
>> but I don't feel strongly about it.
>
>I do not have strong preference either way. Unless this is considered
>better by more people I would stick with what I have.

I agree with Mike.

>-- 
>Michal Hocko
>SUSE Labs

-- 
Wei Yang
Help you, Help me