On Wed 14-02-18 02:28:38, David Rientjes wrote: > On Wed, 14 Feb 2018, Michal Hocko wrote: > > > I do not have any objections regarding the extension. What I am more > > interested in is _why_ people are still using this command line > > parameter at all these days. Why would anybody want to introduce lowmem > > issues from 32b days. I can see the CMA/Hotplug usecases for > > ZONE_MOVABLE but those have their own ways to define zone movable. I was > > tempted to simply remove the kernelcore already. Could you be more > > specific what is your usecase which triggered a need of an easier > > scaling of the size? > > Fragmentation of non-__GFP_MOVABLE pages due to low on memory situations > can pollute most pageblocks on the system, as much as 1GB of slab being > fragmented over 128GB of memory, for example. OK, I was assuming something like that. > When the amount of kernel > memory is well bounded for certain systems, it is better to aggressively > reclaim from existing MIGRATE_UNMOVABLE pageblocks rather than eagerly > fallback to others. > > We have additional patches that help with this fragmentation if you're > interested, specifically kcompactd compaction of MIGRATE_UNMOVABLE > pageblocks triggered by fallback of non-__GFP_MOVABLE allocations and > draining of pcp lists back to the zone free area to prevent stranding. Yes, I think we need a proper fix. (Ab)using zone_movable for this usecase is just sad. -- Michal Hocko SUSE Labs -- 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>
