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authorJiang Liu <liuj97@gmail.com>2012-12-12 13:52:19 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-12 17:38:35 -0800
commit01cefaef40c48c714b7476e62781230993e10dbf (patch)
tree9dc4b2db2a257e1f8a533511dbdfb585712bc380 /mm/page_alloc.c
parent02c0ab684fc41bc13ba8d5ad89b0dc73b092fa08 (diff)
downloadlinux-01cefaef40c48c714b7476e62781230993e10dbf.tar.gz
mm: provide more accurate estimation of pages occupied by memmap
If SPARSEMEM is enabled, it won't build page structures for non-existing pages (holes) within a zone, so provide a more accurate estimation of pages occupied by memmap if there are bigger holes within the zone. And pages for highmem zones' memmap will be allocated from lowmem, so charge nr_kernel_pages for that. [akpm@linux-foundation.org: mark calc_memmap_size __paging_init] Signed-off-by: Jiang Liu <jiang.liu@huawei.com> Cc: Wen Congyang <wency@cn.fujitsu.com> Cc: David Rientjes <rientjes@google.com> Cc: Maciej Rutecki <maciej.rutecki@gmail.com> Cc: Chris Clayton <chris2553@googlemail.com> Cc: "Rafael J . Wysocki" <rjw@sisk.pl> Cc: Mel Gorman <mgorman@suse.de> Cc: Minchan Kim <minchan@kernel.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Michal Hocko <mhocko@suse.cz> Tested-by: Jianguo Wu <wujianguo@huawei.com> Cc: Dave Hansen <dave@linux.vnet.ibm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c26
1 files changed, 24 insertions, 2 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0b6a6d04300..d187988e2b5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4489,6 +4489,26 @@ void __init set_pageblock_order(void)
#endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
+static unsigned long __paginginit calc_memmap_size(unsigned long spanned_pages,
+ unsigned long present_pages)
+{
+ unsigned long pages = spanned_pages;
+
+ /*
+ * Provide a more accurate estimation if there are holes within
+ * the zone and SPARSEMEM is in use. If there are holes within the
+ * zone, each populated memory region may cost us one or two extra
+ * memmap pages due to alignment because memmap pages for each
+ * populated regions may not naturally algined on page boundary.
+ * So the (present_pages >> 4) heuristic is a tradeoff for that.
+ */
+ if (spanned_pages > present_pages + (present_pages >> 4) &&
+ IS_ENABLED(CONFIG_SPARSEMEM))
+ pages = present_pages;
+
+ return PAGE_ALIGN(pages * sizeof(struct page)) >> PAGE_SHIFT;
+}
+
/*
* Set up the zone data structures:
* - mark all pages reserved
@@ -4523,8 +4543,7 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
* is used by this zone for memmap. This affects the watermark
* and per-cpu initialisations
*/
- memmap_pages =
- PAGE_ALIGN(size * sizeof(struct page)) >> PAGE_SHIFT;
+ memmap_pages = calc_memmap_size(size, realsize);
if (freesize >= memmap_pages) {
freesize -= memmap_pages;
if (memmap_pages)
@@ -4545,6 +4564,9 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
if (!is_highmem_idx(j))
nr_kernel_pages += freesize;
+ /* Charge for highmem memmap if there are enough kernel pages */
+ else if (nr_kernel_pages > memmap_pages * 2)
+ nr_kernel_pages -= memmap_pages;
nr_all_pages += freesize;
zone->spanned_pages = size;