Mark sweep garbage collection (GC) is usually implemented using a mark stack for a depth first search that marks all objects reachable from the root set. However, the required size of the mark stack depends on the application, and its upper bound is proportional to the size of the heap. It is not acceptable in most systems to reserve memory for such a large mark stack. To avoid unacceptable memory overhead, some systems limit the size of the mark stack. If the mark stack overflows, the system scans the entire heap to find objects that could not be pushed due to overflow and traverses their children. Since the scanning takes a long time, this technique is inefficient for applications that are likely to cause overflows. In this research, we propose a technique to record rough locations of objects that failed to be pushed so that they can be found without scanning the entire heap. We use a technique similar to the card table of mostly concurrent GC to record rough locations. © 2012 Information Processing Society of Japan.