The boot memory allocator makes assumptions on the alignment of zone boundaries even though the buddy allocator has no requirements on the alignment of zones. This may cause boot problems in situations where ZONE_MOVABLE is populated because the bootmem allocator assumes zones are at least order-log2(BITS_PER_LONG) aligned. As the two potential users (huge pages and memory hot-remove) of ZONE_MOVABLE would prefer a higher alignment, this patch aligns the start of the zone instead of fixing the different assumptions made by the bootmem allocator.
This patch rounds the start of ZONE_MOVABLE in each node to a MAX_ORDER_NR_PAGES boundary. If the rounding pushes the start of ZONE_MOVABLE above the end of the node then the zone will contain no memory and will not be used at runtime. The value is rounded up instead of down as it is better to have the kernel-portion of memory larger than requested instead of smaller. The impact is that the kernel-usable portion of memory because a minimum guarantee instead of the exact size requested by the user. Signed-off-by: Mel Gorman <[EMAIL PROTECTED]> Acked-by: Andy Whitcroft <[EMAIL PROTECTED]> --- page_alloc.c | 5 +++++ 1 files changed, 5 insertions(+) diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.21-rc6-mm1-002_commonparse/mm/page_alloc.c linux-2.6.21-rc6-mm1-003_alignmovable/mm/page_alloc.c --- linux-2.6.21-rc6-mm1-002_commonparse/mm/page_alloc.c 2007-04-24 09:38:30.000000000 +0100 +++ linux-2.6.21-rc6-mm1-003_alignmovable/mm/page_alloc.c 2007-04-24 11:15:40.000000000 +0100 @@ -3642,6 +3642,11 @@ restart: usable_nodes--; if (usable_nodes && required_kernelcore > usable_nodes) goto restart; + + /* Align start of ZONE_MOVABLE on all nids to MAX_ORDER_NR_PAGES */ + for (nid = 0; nid < MAX_NUMNODES; nid++) + zone_movable_pfn[nid] = + roundup(zone_movable_pfn[nid], MAX_ORDER_NR_PAGES); } /** - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/