On Tue, Aug 06, 2013 at 07:22:02AM +0530, Aneesh Kumar K.V wrote: > Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> writes: > >> > >> Considering that we have architectures that won't support migrating > >> explicit hugepages with this patch series, is it ok to use > >> GFP_HIGHUSER_MOVABLE for hugepage allocation ? > > > > Originally this parameter was introduced to make hugepage pool on ZONE_MOVABLE. > > The benefit is that we can extend the hugepage pool more easily, > > because external fragmentation less likely happens than other zone type > > by rearranging fragmented pages with page migration/reclaim. > > > > So I think using ZONE_MOVABLE for hugepage allocation by default makes sense > > even on the architectures which don't support hugepage migration. > > But allocating hugepages from ZONE_MOVABLE means we have pages in that > zone which we can't migrate. Doesn't that impact other features like > hotplug ? Memory blocks occupied by hugepages are not removable before this patchset, whether they are from ZONE_MOVABLE or not, and the hugepage users accepted it for now. So I think this change doesn't make things worse than now. It can be more preferable to switch on/off __GFP_MOVABLE flag depending on archs without using the tunable parameter. I'm ok for this direction, but I want to do it as a separate work. Thanks, Naoya Horiguchi -- 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>