diff options
| author | Dave Hansen <dave@linux.vnet.ibm.com> | 2012-11-21 14:21:51 -0500 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-11-21 12:33:16 -1000 |
| commit | ef6c5be658f6a70c1256fbd18e18ee0dc24c3386 (patch) | |
| tree | d81dfda3c7a7e6a93e5ec6d158e0b42f545bd537 /mm | |
| parent | db9d8c60266a5010e905829e10cd722519e14777 (diff) | |
fix incorrect NR_FREE_PAGES accounting (appears like memory leak)
There have been some 3.7-rc reports of vm issues, including some kswapd
bugs and, more importantly, some memory "leaks":
http://www.spinics.net/lists/linux-mm/msg46187.html
https://bugzilla.kernel.org/show_bug.cgi?id=50181
Commit 1fb3f8ca0e92 ("mm: compaction: capture a suitable high-order page
immediately when it is made available") took split_free_page() and
reused it for the compaction code. It does something curious with
capture_free_page() (previously known as split_free_page()):
int capture_free_page(struct page *page, int alloc_order,
...
__mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order));
- /* Split into individual pages */
- set_page_refcounted(page);
- split_page(page, order);
+ if (alloc_order != order)
+ expand(zone, page, alloc_order, order,
+ &zone->free_area[order], migratetype);
Note that expand() puts the pages _back_ in the allocator, but it does
not bump NR_FREE_PAGES. We "return" 'alloc_order' worth of pages, but
we accounted for removing 'order' in the __mod_zone_page_state() call.
For the old split_page()-style use (order==alloc_order) the bug will not
trigger. But, when called from the compaction code where we
occasionally get a larger page out of the buddy allocator than we need,
we will run in to this.
This patch simply changes the NR_FREE_PAGES manipulation to the correct
'alloc_order' instead of 'order'.
I've been able to repeatedly trigger this in my testing environment.
The amount "leaked" very closely tracks the imbalance I see in buddy
pages vs. NR_FREE_PAGES. I have confirmed that this patch fixes the
imbalance
Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/page_alloc.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 7bb35ac0964a..bcb72c6e2b2d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1405,7 +1405,7 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype) mt = get_pageblock_migratetype(page); if (unlikely(mt != MIGRATE_ISOLATE)) - __mod_zone_freepage_state(zone, -(1UL << order), mt); + __mod_zone_freepage_state(zone, -(1UL << alloc_order), mt); if (alloc_order != order) expand(zone, page, alloc_order, order, |