On 2016/7/19 14:50, Joonsoo Kim wrote: > On Mon, Jul 18, 2016 at 04:31:11PM +0800, Xishi Qiu wrote: >> On 2016/7/18 16:05, Vlastimil Babka wrote: >> >>> On 07/18/2016 10:00 AM, Xishi Qiu wrote: >>>> On 2016/7/18 13:51, Joonsoo Kim wrote: >>>> >>>>> On Fri, Jul 15, 2016 at 10:47:06AM +0800, Xishi Qiu wrote: >>>>>> alloc_migrate_target() is called from migrate_pages(), and the page >>>>>> is always from user space, so we can add __GFP_HIGHMEM directly. >>>>> >>>>> No, all migratable pages are not from user space. For example, >>>>> blockdev file cache has __GFP_MOVABLE and migratable but it has no >>>>> __GFP_HIGHMEM and __GFP_USER. >>>>> >>>> >>>> Hi Joonsoo, >>>> >>>> So the original code "gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;" >>>> is not correct? >>> >>> It's not incorrect. GFP_USER just specifies some reclaim flags, and may perhaps restrict allocation through __GFP_HARDWALL, where the original >>> page could have been allocated without the restriction. But it doesn't put the place in an unexpected address range, as placing a non-highmem page into highmem could. __GFP_MOVABLE then just controls a heuristic for placement within a zone. >>> >>>>> And, zram's memory isn't GFP_HIGHUSER_MOVABLE but has __GFP_MOVABLE. >>>>> >>>> >>>> Can we distinguish __GFP_MOVABLE or GFP_HIGHUSER_MOVABLE when doing >>>> mem-hotplug? >>> >>> I don't understand the question here, can you rephrase with more detail? Thanks. >>> >> >> Hi Joonsoo, > > Above is answered by Vlastimil. :) > >> When we do memory offline, and the zone is movable zone, >> can we use "alloc_pages_node(nid, GFP_HIGHUSER_MOVABLE, 0);" to alloc a >> new page? the nid is the next node. > > I don't know much about memory offline, but, AFAIK, memory offline > could happen on non-movable zone like as ZONE_NORMAL. Perhaps, you can add > "if zone of the page is movable zone then alloc with GFP_HIGHUSER_MOVABLE". > > Thanks. > Hi Joonsoo and Vlastimil, Memory offline could happen on both movable zone and non-movable zone, and we can offline the whole node if the zone is movable_zone(the node only has one movable_zone), and if the zone is normal_zone, we cannot offline the whole node, because some kernel memory can't be migrated. So how about change alloc_migrate_target() to alloc memory from the next node with GFP_HIGHUSER_MOVABLE, if the offline zone is movable_zone. And if the offline zone is normal_zone, we don't change anything, that means the new page may be from the same node. Thanks, Xishi Qiu > . > -- 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>