On 04/12/2018 07:51 AM, Michal Hocko wrote: > On Wed 11-04-18 18:06:59, Laura Abbott wrote: >> >> I took a look at this a little bit more and while it's true we don't >> have the unmovable restriction anymore, CMA is still tied to the pageblock >> size (512MB) because we still have MIGRATE_CMA. I guess making the >> pageblock smaller seems like the most plausible approach? > > Maybe I am wrong but my take on what Joonsoo said is that we really do > not have to care about page blocks and MIGRATE_CMA because GFP_MOVABLE > can be allocated from that migrate type as it is by definition movable. > The size of the page block shouldn't matter. Agree, CMA itself doesn't need mark pageblocks with MIGRATE_CMA anymore. The only user is now hardened usercopy via check_page_span() -> is_migrate_cma_page(). If we could give up the CMA check there (or recognize CMA differently?), MIGRATE_CMA could be removed completely, together with the pageblock alignment code.
