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authorRafael Aquini <aquini@redhat.com>2012-12-12 04:02:38 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-12 05:22:26 +0400
commit18468d93e53b037e1a04ec58398eab763d054064 (patch)
tree74392b876400391567f55bb5292107b65e3791a2 /include/linux/migrate.h
parent252aa6f5be64c90c67b9f066ccff880f6b487d32 (diff)
downloadlinux-18468d93e53b037e1a04ec58398eab763d054064.tar.xz
mm: introduce a common interface for balloon pages mobility
Memory fragmentation introduced by ballooning might reduce significantly the number of 2MB contiguous memory blocks that can be used within a guest, thus imposing performance penalties associated with the reduced number of transparent huge pages that could be used by the guest workload. This patch introduces a common interface to help a balloon driver on making its page set movable to compaction, and thus allowing the system to better leverage the compation efforts on memory defragmentation. [akpm@linux-foundation.org: use PAGE_FLAGS_CHECK_AT_PREP, s/__balloon_page_flags/page_flags_cleared/, small cleanups] [rientjes@google.com: allow balloon compaction for any system with memory compaction enabled, which is the defconfig] Signed-off-by: Rafael Aquini <aquini@redhat.com> Acked-by: Mel Gorman <mel@csn.ul.ie> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/migrate.h')
-rw-r--r--include/linux/migrate.h10
1 files changed, 10 insertions, 0 deletions
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index a4e886d17f87..ce42847ed35f 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -11,8 +11,18 @@ typedef struct page *new_page_t(struct page *, unsigned long private, int **);
* Return values from addresss_space_operations.migratepage():
* - negative errno on page migration failure;
* - zero on page migration success;
+ *
+ * The balloon page migration introduces this special case where a 'distinct'
+ * return code is used to flag a successful page migration to unmap_and_move().
+ * This approach is necessary because page migration can race against balloon
+ * deflation procedure, and for such case we could introduce a nasty page leak
+ * if a successfully migrated balloon page gets released concurrently with
+ * migration's unmap_and_move() wrap-up steps.
*/
#define MIGRATEPAGE_SUCCESS 0
+#define MIGRATEPAGE_BALLOON_SUCCESS 1 /* special ret code for balloon page
+ * sucessful migration case.
+ */
#ifdef CONFIG_MIGRATION