On 11/06/2017 07:32 PM, Michal Hocko wrote: > On Mon 06-11-17 20:13:36, Maxim Levitsky wrote: >> Yes, I tested git head from mainline and few kernels from ubuntu repos >> since I was lazy to compile them too. > > OK, so this hasn't worked realiably as I've suspected. > >> Do you have an idea what can I do about this issue? Do you think its >> feasable to fix this? > > Well, I think that giga pages need quite some love to be usable > reliably. The current implementation is more towards "make it work if > there is enough unused memory". > >> And if not using moveable zone, how would it even be possible to have >> guaranreed allocation of 1g pages > > Having a guaranteed giga pages is something the kernel is not yet ready > to offer. Abusing zone movable might look like the right direction > but that is not really the case until we make sure those pages are > migratable. Migratable where? It's very unlikely you will be able to migrate them away from a movable zone to a normal zone. So the use case is migration between hotplugable nodes, so one of them can be removed? That would probably be an improvement (even if you could not guarantee to offline all hotplugable nodes at once without admin intervention removing those giga pages). Right now the only scenario where giga pages are compatible with hot-remove is to put them on the already-limited non-removable node 0... > There has been a simple patch which makes PUD (1GB) pages migrateable > http://lkml.kernel.org/r/20170913101047.GA13026@xxxxxxxxx but I've had > concerns that it really didn't consider the migration path much > http://lkml.kernel.org/r/20171003073301.hydw7jf2wztsx2om%40dhcp22.suse.cz > I still believe the patch is not complete but maybe it is not that far > away from being so. E.g. the said pfn_range_valid_gigantic can be > enhanced to make the migration much more reliable or get rid of it > altogether because the pfn based allocator already knows how to do > migration and other stuff. > > I can help some with that. > -- 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>
