On 3/22/23 09:46, Matthew Wilcox wrote: > On Wed, Mar 22, 2023 at 09:16:55AM -0700, Dave Hansen wrote: >> 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. > Right, you can construct such a system, but do we support the CONFIG > options of NUMA enabled and SMP disabled? It seems so niche that we > shouldn't be spending time testing that combination. On x86 we don't: > config NUMA > bool "NUMA Memory Allocation and Scheduler Support" > depends on SMP > depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP) ... which I think is fine. I totally agree that NUMA without SMP is too niche to care about. Heck, !SMP is almost too niche to care about these days.
