diff --git a/src/aof.c b/src/aof.c
index bc92cdb98..6289e4dd5 100644
--- a/src/aof.c
+++ b/src/aof.c
@@ -962,6 +962,13 @@ int rewriteAppendOnlyFileBackground(void) {
         if (server.sofd > 0) close(server.sofd);
         snprintf(tmpfile,256,"temp-rewriteaof-bg-%d.aof", (int) getpid());
         if (rewriteAppendOnlyFile(tmpfile) == REDIS_OK) {
+            size_t private_dirty = zmalloc_get_private_dirty();
+
+            if (private_dirty) {
+                redisLog(REDIS_NOTICE,
+                    "AOF rewrite: %lu MB of memory used by copy-on-write",
+                    private_dirty/(1024*1024));
+            }
             exitFromChild(0);
         } else {
             exitFromChild(1);
diff --git a/src/rdb.c b/src/rdb.c
index 193ff5b3b..5a08b6346 100644
--- a/src/rdb.c
+++ b/src/rdb.c
@@ -731,6 +731,15 @@ int rdbSaveBackground(char *filename) {
         if (server.ipfd > 0) close(server.ipfd);
         if (server.sofd > 0) close(server.sofd);
         retval = rdbSave(filename);
+        if (retval == REDIS_OK) {
+            size_t private_dirty = zmalloc_get_private_dirty();
+
+            if (private_dirty) {
+                redisLog(REDIS_NOTICE,
+                    "RDB: %lu MB of memory used by copy-on-write",
+                    private_dirty/(1024*1024));
+            }
+        }
         exitFromChild((retval == REDIS_OK) ? 0 : 1);
     } else {
         /* Parent */