mm: migrate: Introduce migrate_misplaced_page()

Note: This was originally based on Peter's patch "mm/migrate: Introduce
	migrate_misplaced_page()" but borrows extremely heavily from Andrea's
	"autonuma: memory follows CPU algorithm and task/mm_autonuma stats
	collection". The end result is barely recognisable so signed-offs
	had to be dropped. If original authors are ok with it, I'll
	re-add the signed-off-bys.

Add migrate_misplaced_page() which deals with migrating pages from
faults.

Based-on-work-by: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Based-on-work-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Based-on-work-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>

1 files changed, 106 insertions, 2 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index 27be9c923dc1..d168aec98427 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -282,7 +282,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
                 struct page *newpage, struct page *page,
                 struct buffer_head *head, enum migrate_mode mode)
 {
-        int expected_count;
+        int expected_count = 0;
         void **pslot;
 
         if (!mapping) {
@@ -1415,4 +1415,108 @@ int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
         }
         return err;
 }
-#endif
+
+#ifdef CONFIG_NUMA_BALANCING
+/*
+ * Returns true if this is a safe migration target node for misplaced NUMA
+ * pages. Currently it only checks the watermarks which crude
+ */
+static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
+                                   int nr_migrate_pages)
+{
+        int z;
+        for (z = pgdat->nr_zones - 1; z >= 0; z--) {
+                struct zone *zone = pgdat->node_zones + z;
+
+                if (!populated_zone(zone))
+                        continue;
+
+                if (zone->all_unreclaimable)
+                        continue;
+
+                /* Avoid waking kswapd by allocating pages_to_migrate pages. */
+                if (!zone_watermark_ok(zone, 0,
+                                       high_wmark_pages(zone) +
+                                       nr_migrate_pages,
+                                       0, 0))
+                        continue;
+                return true;
+        }
+        return false;
+}
+
+static struct page *alloc_misplaced_dst_page(struct page *page,
+                                           unsigned long data,
+                                           int **result)
+{
+        int nid = (int) data;
+        struct page *newpage;
+
+        newpage = alloc_pages_exact_node(nid,
+                                         (GFP_HIGHUSER_MOVABLE | GFP_THISNODE |
+                                          __GFP_NOMEMALLOC | __GFP_NORETRY |
+                                          __GFP_NOWARN) &
+                                         ~GFP_IOFS, 0);
+        return newpage;
+}
+
+/*
+ * Attempt to migrate a misplaced page to the specified destination
+ * node. Caller is expected to have an elevated reference count on
+ * the page that will be dropped by this function before returning.
+ */
+int migrate_misplaced_page(struct page *page, int node)
+{
+        int isolated = 0;
+        LIST_HEAD(migratepages);
+
+        /*
+         * Don't migrate pages that are mapped in multiple processes.
+         * TODO: Handle false sharing detection instead of this hammer
+         */
+        if (page_mapcount(page) != 1) {
+                put_page(page);
+                goto out;
+        }
+
+        /* Avoid migrating to a node that is nearly full */
+        if (migrate_balanced_pgdat(NODE_DATA(node), 1)) {
+                int page_lru;
+
+                if (isolate_lru_page(page)) {
+                        put_page(page);
+                        goto out;
+                }
+                isolated = 1;
+
+                /*
+                 * Page is isolated which takes a reference count so now the
+                 * callers reference can be safely dropped without the page
+                 * disappearing underneath us during migration
+                 */
+                put_page(page);
+
+                page_lru = page_is_file_cache(page);
+                inc_zone_page_state(page, NR_ISOLATED_ANON + page_lru);
+                list_add(&page->lru, &migratepages);
+        }
+
+        if (isolated) {
+                int nr_remaining;
+
+                nr_remaining = migrate_pages(&migratepages,
+                                alloc_misplaced_dst_page,
+                                node, false, MIGRATE_ASYNC,
+                                MR_NUMA_MISPLACED);
+                if (nr_remaining) {
+                        putback_lru_pages(&migratepages);
+                        isolated = 0;
+                }
+        }
+        BUG_ON(!list_empty(&migratepages));
+out:
+        return isolated;
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
+#endif /* CONFIG_NUMA */