On Tue 08-09-20 10:41:10, Rik van Riel wrote: > On Tue, 2020-09-08 at 16:35 +0200, Michal Hocko wrote: > > > A global knob is insufficient. 1G pages will become a very precious > > resource as it requires a pre-allocation (reservation). So it really > > has > > to be an opt-in and the question is whether there is also some sort > > of > > access control needed. > > The 1GB pages do not require that much in the way of > pre-allocation. The memory can be obtained through CMA, > which means it can be used for movable 4kB and 2MB > allocations when not > being used for 1GB pages. That CMA has to be pre-reserved, right? That requires a configuration. > That makes it relatively easy to set aside > some fraction > of system memory in every system for 1GB and movable > allocations, and use it for whatever way it is needed > depending on what workload(s) end up running on a system. I was not talking about how easy or hard it is. My main concern is that this is effectively a pre-reserved pool and a global knob is a very suboptimal way to control access to it. I (rather) strongly believe this should be an explicit opt-in and ideally not 1GB specific but rather something to allow large pages to be created as there is a fit. See other subthread for more details. -- Michal Hocko SUSE Labs
