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. Before onlining, it's just setting node_start_pfn to *some value* to be overwritten in move_pfn_range_to_zone()->resize_pgdat_range(). (I have some more patches to clean up __try_online_node(), and this change here makes it clear that there isn't any magic happening in __try_online_node() related to the start pfn and memblocks - see patch #2) -- Thanks, David / dhildenb
