linux-kernel - Re: [PATCH 2/6] mm/memblock: make full utilization of numa info

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Date:   Mon, 25 Feb 2019 07:34:03 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Pingfan Liu <kernelfans@...il.com>, x86@...nel.org,
        linux-mm@...ck.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Petr Tesarik <ptesarik@...e.cz>,
        Michal Hocko <mhocko@...e.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Jonathan Corbet <corbet@....net>,
        Nicholas Piggin <npiggin@...il.com>,
        Daniel Vacek <neelx@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] mm/memblock: make full utilization of numa info

On 2/24/19 4:34 AM, Pingfan Liu wrote:
> +/*
> + * build_node_order() relies on cpumask_of_node(), hence arch should 
> + * set up cpumask before calling this func.
> + */

Whenever I see comments like this, I wonder what happens if the arch
doesn't do this?  Do we just crash in early boot in wonderful new ways?
 Or do we get a nice message telling us?

> +void __init memblock_build_node_order(void)
> +{
> +	int nid, i;
> +	nodemask_t used_mask;
> +
> +	node_fallback = memblock_alloc(MAX_NUMNODES * sizeof(int *),
> +		sizeof(int *));
> +	for_each_online_node(nid) {
> +		node_fallback[nid] = memblock_alloc(
> +			num_online_nodes() * sizeof(int), sizeof(int));
> +		for (i = 0; i < num_online_nodes(); i++)
> +			node_fallback[nid][i] = NUMA_NO_NODE;
> +	}
> +
> +	for_each_online_node(nid) {
> +		nodes_clear(used_mask);
> +		node_set(nid, used_mask);
> +		build_node_order(node_fallback[nid], num_online_nodes(),
> +			nid, &used_mask);
> +	}
> +}

This doesn't get used until patch 6 as far as I can tell.  Was there a
reason to define it here?