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authorAndrea Arcangeli <aarcange@redhat.com>2011-01-13 15:47:00 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-13 17:32:43 -0800
commit5f24ce5fd34c3ca1b3d10d30da754732da64d5c0 (patch)
treec82d27461f2adda210e77808b7dd04eaec017f2f /mm/page_alloc.c
parent21ae5b01750f14140809508a478a4413792e0261 (diff)
downloadop-kernel-dev-5f24ce5fd34c3ca1b3d10d30da754732da64d5c0.zip
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thp: remove PG_buddy
PG_buddy can be converted to _mapcount == -2. So the PG_compound_lock can be added to page->flags without overflowing (because of the sparse section bits increasing) with CONFIG_X86_PAE=y and CONFIG_X86_PAT=y. This also has to move the memory hotplug code from _mapcount to lru.next to avoid any risk of clashes. We can't use lru.next for PG_buddy removal, but memory hotplug can use lru.next even more easily than the mapcount instead. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> 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.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e7664b9..9dfe49b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -449,8 +449,8 @@ __find_combined_index(unsigned long page_idx, unsigned int order)
* (c) a page and its buddy have the same order &&
* (d) a page and its buddy are in the same zone.
*
- * For recording whether a page is in the buddy system, we use PG_buddy.
- * Setting, clearing, and testing PG_buddy is serialized by zone->lock.
+ * For recording whether a page is in the buddy system, we set ->_mapcount -2.
+ * Setting, clearing, and testing _mapcount -2 is serialized by zone->lock.
*
* For recording page's order, we use page_private(page).
*/
@@ -483,7 +483,7 @@ static inline int page_is_buddy(struct page *page, struct page *buddy,
* as necessary, plus some accounting needed to play nicely with other
* parts of the VM system.
* At each level, we keep a list of pages, which are heads of continuous
- * free pages of length of (1 << order) and marked with PG_buddy. Page's
+ * free pages of length of (1 << order) and marked with _mapcount -2. Page's
* order is recorded in page_private(page) field.
* So when we are allocating or freeing one, we can derive the state of the
* other. That is, if we allocate a small block, and both were
@@ -5574,7 +5574,6 @@ static struct trace_print_flags pageflag_names[] = {
{1UL << PG_swapcache, "swapcache" },
{1UL << PG_mappedtodisk, "mappedtodisk" },
{1UL << PG_reclaim, "reclaim" },
- {1UL << PG_buddy, "buddy" },
{1UL << PG_swapbacked, "swapbacked" },
{1UL << PG_unevictable, "unevictable" },
#ifdef CONFIG_MMU
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