On Fri, 11 Jul 2014, Tejun Heo wrote: > On Fri, Jul 11, 2014 at 10:55:59AM -0500, Christoph Lameter wrote: > > > Where X is the memless node. num_mem_id() on X would return either B > > > or C, right? If B or C can't satisfy the allocation, the allocator > > > would fallback to A from B and D for C, both of which aren't optimal. > > > It should first fall back to C or B respectively, which the allocator > > > can't do anymoe because the information is lost when the caller side > > > performs numa_mem_id(). > > > > True but the advantage is that the numa_mem_id() allows the use of a > > consitent sort of "local" node which increases allocator performance due > > to the abillity to cache objects from that node. > > But the allocator can do the mapping the same. I really don't see why > we'd push the distinction to the individual users. The "users" (I guess you mean general kernel code/drivers) can use various memory allocators which will do the right thing internally regarding GFP_THISNODE. They do not need to worry too much about this unless there are reasons beyond optimizing NUMA placement to need memory from a particuylar node (f.e. a device that requires memory from a numa node that is local to the PCI bus where the hardware resides). -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>