On Fri 12-07-19 15:37:30, Will Deacon wrote: > Hi all, > > On Fri, Jul 12, 2019 at 02:12:23PM +0200, Michal Hocko wrote: > > On Fri 12-07-19 10:56:47, Hoan Tran OS wrote: > > [...] > > > It would be good if we can enable it by-default. Otherwise, let arch > > > enables it by them-self. Do you have any suggestions? > > > > I can hardly make any suggestions when it is not really clear _why_ you > > want to remove this config option in the first place. Please explain > > what motivated you to make this change. > > Sorry, I think this confusion might actually be my fault and Hoan has just > been implementing my vague suggestion here: > > https://lore.kernel.org/linux-arm-kernel/20190625101245.s4vxfosoop52gl4e@willie-the-truck/ > > If the preference of the mm folks is to leave CONFIG_NODES_SPAN_OTHER_NODES > as it is, then we can define it for arm64. I just find it a bit weird that > the majority of NUMA-capable architectures have to add a symbol in the arch > Kconfig file, for what appears to be a performance optimisation applicable > only to ia64, mips and sh. > > At the very least we could make the thing selectable. Hmm, I thought this was selectable. But I am obviously wrong here. Looking more closely, it seems that this is indeed only about __early_pfn_to_nid and as such not something that should add a config symbol. This should have been called out in the changelog though. Also while at it, does HAVE_MEMBLOCK_NODE_MAP fall into a similar bucket? Do we have any NUMA architecture that doesn't enable it? Thanks! -- Michal Hocko SUSE Labs
