On Tue, Apr 09, 2013 at 05:27:44PM -0400, KOSAKI Motohiro wrote: > >> numa_node_id() is really silly. This might lead to allocate from offlining node. > > > > Right, it should've been alloc_huge_page(). > > > >> and, offline_pages() should mark hstate as isolated likes normal pages for prohibiting > >> new allocation at first. > > > > It seems that alloc_migrate_target() calls alloc_page() for normal pages > > and the destination pages can be in the same node with the source pages > > (new page allocation from the same memblock are prohibited.) > > No. It can't. memory hotplug change buddy attribute to MIGRATE_ISOLTE at first. > then alloc_page() never allocate from source node. however huge page don't use > buddy. then we need another trick. MIGRATE_ISOLTE is changed only within the range [start_pfn, end_pfn) given as the argument of __offline_pages (see also start_isolate_page_range), so it's set only for pages within the single memblock to be offlined. BTW, in previous discussion I already agreed with checking migrate type in hugepage allocation code (maybe it will be in dequeue_huge_page_vma(),) so what you concern should be solved in the next post. > > > So if we want to avoid new page allocation from the same node, > > this is the problem both for normal and huge pages. > > > > BTW, is it correct to think that all users of memory hotplug assume > > that they want to hotplug a whole node (not the part of it?) > > Both are valid use case. admin can isolate a part of memory for isolating > broken memory range. > > but I'm sure almost user want to remove whole node. OK. So I think about "allocation in the nearest neighbor node", although it can be in separate patch if it's hard to implement. Thanks, Naoya -- 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>