linux-kernel - Re: [RFC][PATCH 05/13] mm/numa: automatically generate node migration order

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Date:   Tue, 2 Feb 2021 12:43:03 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Yang Shi <shy828301@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        David Rientjes <rientjes@...gle.com>,
        Huang Ying <ying.huang@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        David Hildenbrand <david@...hat.com>
Subject: Re: [RFC][PATCH 05/13] mm/numa: automatically generate node
 migration order

On Mon, Feb 01, 2021 at 11:13:14AM -0800, Dave Hansen wrote:
> Sure.  Were you thinking of a code comment, or enhanced changelog?
> 
> Let's say there's a system with two sockets each with the same three
> classes of memory: fast, medium and slow.  Each memory class is placed
> in its own NUMA node and the CPUs are attached to the fast memory.  That
> leaves 6 NUMA nodes (0-5):
> 
> 	Socket A: 0, 1, 2
> 	Socket B: 3, 4, 5
> 
> The migration path for this configuration path would start on the nodes
> with the processors and fast memory, progress through medium and end
> with the slow memory:
> 
> 	0 -> 1 -> 2 -> stop
> 	3 -> 4 -> 5 -> stop
> 
> This is represented in the node_demotion[] like this:
> 
> 	{  1, // Node 0 migrates to 1
> 	   2, // Node 1 migrates to 2
> 	  -1, // Node 2 does not migrate
> 	   4, // Node 3 migrates to 1
> 	   5, // Node 4 migrates to 2
> 	  -1} // Node 5 does not migrate
> 
> Is that what you were thinking of?

I would not mind to have the above explanation in a comment somewhere
in the code.


-- 
Oscar Salvador
SUSE L3