Re: [PATCH] mm/slab: Fix undefined init_cache_node_node() for NUMA and !SMP

[Dave Hansen]

On 3/21/23 09:40, Matthew Wilcox wrote:
> On Tue, Mar 21, 2023 at 09:30:59AM +0100, Geert Uytterhoeven wrote:
>> -#if (defined(CONFIG_NUMA) && defined(CONFIG_MEMORY_HOTPLUG)) || defined(CONFIG_SMP)
>> +#if defined(CONFIG_NUMA) || defined(CONFIG_SMP)
> I'm amused by the thought of CONFIG_NUMA without CONFIG_SMP.
> Is it possible to have one node with memory and a single CPU, then
> another node with memory and no CPU?

It's _possible_ for sure, just unlikely.  The most likely place these
days is probably a teensy tiny VM that just happens to have some
performance-differentiated memory exposed to it for some reason.  Maybe
it's got a slice of slow PMEM or fast High-Bandwidth memory for whatever
reason.