Index: memtester.c
--- memtester.c.orig
+++ memtester.c
@@ -343,7 +343,7 @@ int main(int argc, char **argv) {
                         wantbytes = wantbytes_orig;
                         break;
                     default:
-                        printf("failed for unknown reason.\n");
+                        printf("mlock: %s\n", strerror(errno));
                         do_mlock = 0;
                         done_mem = 1;
                 }