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SubjectRe: [PATCH v5 3/3] mm/page_alloc: Keep memoryless cpuless node 0 offline
* Christopher Lameter <cl@linux.com> [2020-06-29 14:58:40]:

> On Wed, 24 Jun 2020, Srikar Dronamraju wrote:
>
> > Currently Linux kernel with CONFIG_NUMA on a system with multiple
> > possible nodes, marks node 0 as online at boot. However in practice,
> > there are systems which have node 0 as memoryless and cpuless.
>
> Maybe add something to explain why you are not simply mapping the
> existing memory to NUMA node 0 which is after all just a numbering scheme
> used by the kernel and can be used arbitrarily?
>

I thought Michal Hocko already gave a clear picture on why mapping is a bad
idea. https://lore.kernel.org/lkml/20200316085425.GB11482@dhcp22.suse.cz/t/#u
Are you suggesting that we add that as part of the changelog?

> This could be seen more as a bug in the arch code during the setup of NUMA
> nodes. The two nodes are created by the firmwware / bootstrap code after
> all. Just do not do it?
>

- The arch/setup code in powerpc is not onlining these nodes.
- Later on cpus/memory in node 0 can be onlined.
- Firmware in this case Phyp is an independent code by itself.

--
Thanks and Regards
Srikar Dronamraju

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