On Sun, 7 Feb 2021, Song Bao Hua (Barry Song) wrote: > NUMA balancer is just one of many reasons for page migration. Even one > simple alloc_pages() can cause memory migration in just single NUMA > node or UMA system. > > The other reasons for page migration include but are not limited to: > * memory move due to CMA > * memory move due to huge pages creation > > Hardly we can ask users to disable the COMPACTION, CMA and Huge Page > in the whole system. > What about only for mlocked memory, i.e. disable vm.compact_unevictable_allowed? Adding syscalls is a big deal, we can make a reasonable inference that we'll have to support this forever if it's merged. I haven't seen mention of what other unevictable memory *should* be migratable that would be adversely affected if we disable that sysctl. Maybe that gets you part of the way there and there are some other deficiencies, but it seems like a good start would be to describe how CONFIG_NUMA_BALANCING=n + vm.compact_unevcitable_allowed + mlock() doesn't get you mostly there and then look into what's missing. If it's a very compelling case where there simply are no alternatives, it would make sense. Alternative is to find a more generic way, perhaps in combination with vm.compact_unevictable_allowed, to achieve what you're looking to do that can be useful even beyond your originally intended use case.
