On Wed, 1 Sep 2010 14:41:38 +0200 Michal Hocko <mhocko@xxxxxxx> wrote: > On Wed 01-09-10 14:19:51, Michal Hocko wrote: > > On Tue 31-08-10 22:19:42, Wu Fengguang wrote: > > > On Mon, Aug 23, 2010 at 05:22:46PM +0800, Michal Hocko wrote: > > > > On Sun 22-08-10 08:42:32, Wu Fengguang wrote: > > > > > Hi Michal, > > > > > > > > Hi, > > > > > > > > > > > > > > It helps to explain in changelog/code > > > > > > > > > > - in what situation a ZONE_MOVABLE will contain !MIGRATE_MOVABLE > > > > > pages? > > > > > > > > page can be MIGRATE_RESERVE IIUC. > > > > > > Yup, it may also be set to MIGRATE_ISOLATE by soft_offline_page(). > > > > Doesn't it make sense to check for !MIGRATE_UNMOVABLE then? > > Something like the following patch. > > > From de85f1aa42115678d3340f0448cd798577036496 Mon Sep 17 00:00:00 2001 > From: Michal Hocko <mhocko@xxxxxxx> > Date: Fri, 20 Aug 2010 15:39:16 +0200 > Subject: [PATCH] Make is_mem_section_removable more conformable with offlining code > > Currently is_mem_section_removable checks whether each pageblock from > the given pfn range is of MIGRATE_MOVABLE type or if it is free. If both > are false then the range is considered non removable. > > On the other hand, offlining code (more specifically > set_migratetype_isolate) doesn't care whether a page is free and instead > it just checks the migrate type of the page and whether the page's zone > is movable. > > This can lead into a situation when we can mark a node as not removable > just because a pageblock is MIGRATE_RESERVE and it is not free. > > Let's make a common helper is_page_removable which unifies both tests > at one place. Also let's check for MIGRATE_UNMOVABLE rather than all > possible MIGRATEable types. > > Signed-off-by: Michal Hocko <mhocko@xxxxxxx> Hmm..Why MIGRATE_RECLAIMABLE is included ? If MIGRATE_RCLAIMABLE is included, set_migrate_type() should check the range of pages. Because it makes the pageblock as MIGRAGE_MOVABLE after failure of memory hotplug. Original code checks. - the range is MIGRAGE_MOVABLE or - the range includes only free pages and LRU pages. Then, moving them back to MIGRAGE_MOVABLE after failure was correct. Doesn't this makes changes MIGRATE_RECALIMABLE to be MIGRATE_MOVABLE and leads us to more fragmentated situation ? Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>