Messages in this thread | | | Date | Tue, 26 Aug 2008 10:29:29 +0100 | From | Andy Whitcroft <> | Subject | Re: [BUG] [PATCH v2] Make setup_zone_migrate_reserve() aware of overlapping nodes |
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On Thu, Aug 21, 2008 at 12:33:39PM +0100, Mel Gorman wrote: > On (20/08/08 14:55), Adam Litke didst pronounce: > > Changes since V1 > > - Fix build for !NUMA > > - Add VM_BUG_ON() to catch this problem at the source > > > > I have gotten to the root cause of the hugetlb badness I reported back on > > August 15th. My system has the following memory topology (note the > > overlapping node): > > > > Node 0 Memory: 0x8000000-0x44000000 > > Node 1 Memory: 0x0-0x8000000 0x44000000-0x80000000 > > > > setup_zone_migrate_reserve() scans the address range 0x0-0x8000000 looking > > for a pageblock to move onto the MIGRATE_RESERVE list. Finding no > > candidates, it happily continues the scan into 0x8000000-0x44000000. When > > a pageblock is found, the pages are moved to the MIGRATE_RESERVE list on > > the wrong zone. Oops. > > > > (Andrew: once the proper fix is agreed upon, this should also be a > > candidate for -stable.) > > > > setup_zone_migrate_reserve() should skip pageblocks in overlapping nodes. > > > > Signed-off-by: Adam Litke <agl@us.ibm.com> > > > > zone_to_nid(zone) is called every time in the loop even though it will never > change. This is less than optimal but setup_zone_migrate_reserve() is only > called during init and when min_free_kbytes is adjusted so it's not worth > worrying about. Otherwise it looks good. > > Acked-by: Mel Gorman <mel@csn.ul.ie> > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index af982f7..feb7916 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -694,6 +694,9 @@ static int move_freepages(struct zone *zone, > > #endif > > > > for (page = start_page; page <= end_page;) { > > + /* Make sure we are not inadvertently changing nodes */ > > + VM_BUG_ON(page_to_nid(page) != zone_to_nid(zone)); > > + > > if (!pfn_valid_within(page_to_pfn(page))) { > > page++; > > continue; > > @@ -2516,6 +2519,10 @@ static void setup_zone_migrate_reserve(struct zone *zone) > > continue; > > page = pfn_to_page(pfn); > > > > + /* Watch out for overlapping nodes */ > > + if (page_to_nid(page) != zone_to_nid(zone)) > > + continue; > > + > > /* Blocks with reserved pages will never free, skip them. */ > > if (PageReserved(page)) > > continue;
This patch looks sane. I do note that we have a config option to tell us whether we have any possibility of overlapping nodes, and we have an early version of a check for this early_pfn_in_nid() in mm.h. You might consider having a non-early variant of this which could be optimised away for those arches which do not have CONFIG_NODES_SPAN_OTHER_NODES.
In 'unearlifying' this to pfn_in_nid() I think we have a small naming issue with these function as they are only valid for use with pfns within an existing node. They should probabally both be *pfn_in_nid_within() or something in line with pfn_valid_within().
-apw
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