On Tue 21-04-20 14:35:12, David Hildenbrand wrote: > On 21.04.20 14:30, Michal Hocko wrote: > > Sorry for the late reply > > > > On Thu 16-04-20 12:47:06, David Hildenbrand wrote: > >> A hotadded node/pgdat will span no pages at all, until memory is moved to > >> the zone/node via move_pfn_range_to_zone() -> resize_pgdat_range - e.g., > >> when onlining memory blocks. We don't have to initialize the > >> node_start_pfn to the memory we are adding. > > > > You are right that the node is empty at this phase but that is already > > reflected by zero present pages (hmm, I do not see spanned pages to be > > set 0 though). What I am missing here is why this is an improvement. The > > new node is already visible here and I do not see why we hide the > > information we already know. > > "information we already know" - no, not before we online the memory. Is this really the case? All add_memory_resource users operate on a physical memory range. > Before onlining, it's just setting node_start_pfn to *some value* to be > overwritten in move_pfn_range_to_zone()->resize_pgdat_range(). Yes the value is overwritten but I am not sure this is actually correct thing to do. I cannot remember why I've chosen to do that. It doesn't really seem unlikely to online node in a higher physical address. Btw. one thing that I have in my notes, I was never able to actually test the no numa node case. Because I have always been testing with node being allocated during the boot. Do you have any way to trigger this path? -- Michal Hocko SUSE Labs
