mm: introduce compaction and migration for ballooned pages

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 the helper functions as well as the necessary changes
to teach compaction and migration bits how to cope with pages which are
part of a guest memory balloon, in order to make them movable by memory
compaction procedures.

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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 2 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index 694eaab..470474c 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -14,6 +14,7 @@
 #include <linux/backing-dev.h>
 #include <linux/sysctl.h>
 #include <linux/sysfs.h>
+#include <linux/balloon_compaction.h>
 #include "internal.h"
 
 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
@@ -565,9 +566,24 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
 			goto next_pageblock;
 		}
 
-		/* Check may be lockless but that's ok as we recheck later */
-		if (!PageLRU(page))
+		/*
+		 * Check may be lockless but that's ok as we recheck later.
+		 * It's possible to migrate LRU pages and balloon pages
+		 * Skip any other type of page
+		 */
+		if (!PageLRU(page)) {
+			if (unlikely(balloon_page_movable(page))) {
+				if (locked && balloon_page_isolate(page)) {
+					/* Successfully isolated */
+					cc->finished_update_migrate = true;
+					list_add(&page->lru, migratelist);
+					cc->nr_migratepages++;
+					nr_isolated++;
+					goto check_compact_cluster;
+				}
+			}
 			continue;
+		}
 
 		/*
 		 * PageLRU is set. lru_lock normally excludes isolation
@@ -621,6 +637,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
 		cc->nr_migratepages++;
 		nr_isolated++;
 
+check_compact_cluster:
 		/* Avoid isolating too much */
 		if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
 			++low_pfn;