path: root/mm/highmem.c
diff options
authorMel Gorman <mel@csn.ul.ie>2007-07-17 04:03:12 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-17 10:22:59 -0700
commit2a1e274acf0b1c192face19a4be7c12d4503eaaf (patch)
treef7e98e1fe19d38bb10bf178fb8f8ed1789b659b2 /mm/highmem.c
parent769848c03895b63e5662eb7e4ec8c4866f7d0183 (diff)
Create the ZONE_MOVABLE zone
The following 8 patches against 2.6.20-mm2 create a zone called ZONE_MOVABLE that is only usable by allocations that specify both __GFP_HIGHMEM and __GFP_MOVABLE. This has the effect of keeping all non-movable pages within a single memory partition while allowing movable allocations to be satisfied from either partition. The patches may be applied with the list-based anti-fragmentation patches that groups pages together based on mobility. The size of the zone is determined by a kernelcore= parameter specified at boot-time. This specifies how much memory is usable by non-movable allocations and the remainder is used for ZONE_MOVABLE. Any range of pages within ZONE_MOVABLE can be released by migrating the pages or by reclaiming. When selecting a zone to take pages from for ZONE_MOVABLE, there are two things to consider. First, only memory from the highest populated zone is used for ZONE_MOVABLE. On the x86, this is probably going to be ZONE_HIGHMEM but it would be ZONE_DMA on ppc64 or possibly ZONE_DMA32 on x86_64. Second, the amount of memory usable by the kernel will be spread evenly throughout NUMA nodes where possible. If the nodes are not of equal size, the amount of memory usable by the kernel on some nodes may be greater than others. By default, the zone is not as useful for hugetlb allocations because they are pinned and non-migratable (currently at least). A sysctl is provided that allows huge pages to be allocated from that zone. This means that the huge page pool can be resized to the size of ZONE_MOVABLE during the lifetime of the system assuming that pages are not mlocked. Despite huge pages being non-movable, we do not introduce additional external fragmentation of note as huge pages are always the largest contiguous block we care about. Credit goes to Andy Whitcroft for catching a large variety of problems during review of the patches. This patch creates an additional zone, ZONE_MOVABLE. This zone is only usable by allocations which specify both __GFP_HIGHMEM and __GFP_MOVABLE. Hot-added memory continues to be placed in their existing destination as there is no mechanism to redirect them to a specific zone. [y-goto@jp.fujitsu.com: Fix section mismatch of memory hotplug related code] [akpm@linux-foundation.org: various fixes] Signed-off-by: Mel Gorman <mel@csn.ul.ie> Cc: Andy Whitcroft <apw@shadowen.org> Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com> Cc: William Lee Irwin III <wli@holomorphy.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/highmem.c')
1 files changed, 6 insertions, 1 deletions
diff --git a/mm/highmem.c b/mm/highmem.c
index be8f8d36a8b..7a967bc3515 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -46,9 +46,14 @@ unsigned int nr_free_highpages (void)
pg_data_t *pgdat;
unsigned int pages = 0;
- for_each_online_pgdat(pgdat)
+ for_each_online_pgdat(pgdat) {
pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
+ if (zone_movable_is_highmem())
+ pages += zone_page_state(
+ &pgdat->node_zones[ZONE_MOVABLE],
+ }
return pages;