Re: [LSF/MM TOPIC] CMA and larger page sizes

[Michal Hocko <mhocko@suse.com>]

On Wed 11-04-18 18:06:59, Laura Abbott wrote:
> On 04/11/2018 01:02 PM, Vlastimil Babka wrote:
> > On 04/11/2018 09:55 PM, Laura Abbott wrote:
> > > On 04/03/2018 10:11 PM, Joonsoo Kim wrote:
> > > > If the patchset 'manage the memory of the CMA area by using the ZONE_MOVABLE' is
> > > > merged, this restriction can be removed since there is no unmovable
> > > > pageblock in ZONE_MOVABLE. Just quick thought. :)
> > > > 
> > > > Thanks.
> > > > 
> > > 
> > > Thanks for that pointer. What's the current status of that patchset? Was that
> > > one that needed more review/testing?
> > 
> > It was merged by Linus today, see around commit bad8c6c0b114 ("mm/cma:
> > manage the memory of the CMA area by using the ZONE_MOVABLE")
> > 
> > Congrats, Joonsoo :)
> > 
> 
> 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.
-- 
Michal Hocko
SUSE Labs