On Thu 11-07-19 23:25:44, Hoan Tran OS wrote: > In NUMA layout which nodes have memory ranges that span across other nodes, > the mm driver can detect the memory node id incorrectly. > > For example, with layout below > Node 0 address: 0000 xxxx 0000 xxxx > Node 1 address: xxxx 1111 xxxx 1111 > > Note: > - Memory from low to high > - 0/1: Node id > - x: Invalid memory of a node > > When mm probes the memory map, without CONFIG_NODES_SPAN_OTHER_NODES > config, mm only checks the memory validity but not the node id. > Because of that, Node 1 also detects the memory from node 0 as below > when it scans from the start address to the end address of node 1. > > Node 0 address: 0000 xxxx xxxx xxxx > Node 1 address: xxxx 1111 1111 1111 > > This layout could occur on any architecture. This patch enables > CONFIG_NODES_SPAN_OTHER_NODES by default for NUMA to fix this issue. Yes it can occur on any arch but most sane platforms simply do not overlap physical ranges. So I do not really see any reason to unconditionally enable the config for everybody. What is an advantage? -- Michal Hocko SUSE Labs
