The patch titled Subject: mm: fix incorrect NR_FREE_PAGES accounting (appears like memory leak) has been added to the -mm tree. Its filename is mm-fix-incorrect-nr_free_pages-accounting-appears-like-memory-leak.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> Subject: mm: 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 The post-3.6 commit 1fb3f8ca ("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@xxxxxxxxxxxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxx> Reported-by: Milos Jakovljevic <sukijaki@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN mm/page_alloc.c~mm-fix-incorrect-nr_free_pages-accounting-appears-like-memory-leak mm/page_alloc.c --- a/mm/page_alloc.c~mm-fix-incorrect-nr_free_pages-accounting-appears-like-memory-leak +++ a/mm/page_alloc.c @@ -1405,7 +1405,7 @@ int capture_free_page(struct page *page, 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, _ Patches currently in -mm which might be from dave@xxxxxxxxxxxxxxxxxx are mm-fix-incorrect-nr_free_pages-accounting-appears-like-memory-leak.patch memory-hotplug-update-mce_bad_pages-when-removing-the-memory.patch memory-hotplug-update-mce_bad_pages-when-removing-the-memory-fix.patch memory-hotplug-auto-offline-page_cgroup-when-onlining-memory-block-failed.patch memory-hotplug-fix-nr_free_pages-mismatch.patch memory-hotplug-mm-sparsec-clear-the-memory-to-store-struct-page.patch memory-hotplug-allocate-zones-pcp-before-onlining-pages.patch drop_caches-add-some-documentation-and-info-messsge.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html