linux-kernel - Re: [PATCH 3/3] mm/page_alloc: Keep memoryless cpuless node 0 offline

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Date:   Wed, 18 Mar 2020 18:57:07 +0000 (UTC)
From:   Christopher Lameter <cl@...ux.com>
To:     Michal Hocko <mhocko@...nel.org>
cc:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 3/3] mm/page_alloc: Keep memoryless cpuless node 0
 offline

On Mon, 16 Mar 2020, Michal Hocko wrote:

> > We can dynamically number the nodes right? So just make sure that the
> > firmware properly creates memory on node 0?
>
> Are you suggesting that the OS would renumber NUMA nodes coming
> from FW just to satisfy node 0 existence? If yes then I believe this is
> really a bad idea because it would make HW/LPAR configuration matching
> to the resulting memory layout really hard to follow.

NUMA nodes are created by the OS based on information provided by the
firmware. Either the FW would need to ensure that a viable node 0 exists
or the bootstrap arch code could setup things to the same effect.