[PATCHv2 1/3] zsmalloc: do not scan for allocated objects in empty zspage

[Sergey Senozhatsky]

zspage migration can terminate as soon as it moves the last
allocated object from the source zspage.  Add a simple helper
zspage_empty() that tests zspage ->inuse on each migration
iteration.

Suggested-by: Alexey Romanov <AVRomanov@xxxxxxxxxxxxxx>
Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
---
 mm/zsmalloc.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 3f057970504e..5d60eaedc3b7 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1147,6 +1147,11 @@ static bool zspage_full(struct size_class *class, struct zspage *zspage)
 	return get_zspage_inuse(zspage) == class->objs_per_zspage;
 }
 
+static bool zspage_empty(struct zspage *zspage)
+{
+	return get_zspage_inuse(zspage) == 0;
+}
+
 /**
  * zs_lookup_class_index() - Returns index of the zsmalloc &size_class
  * that hold objects of the provided size.
@@ -1625,6 +1630,10 @@ static void migrate_zspage(struct zs_pool *pool, struct size_class *class,
 		obj_idx++;
 		record_obj(handle, free_obj);
 		obj_free(class->size, used_obj);
+
+		/* Stop if there are no more objects to migrate */
+		if (zspage_empty(get_zspage(s_page)))
+			break;
 	}
 
 	/* Remember last position in this iteration */
-- 
2.41.0.162.gfafddb0af9-goog