After a full-gc, young-gen is usually empty. However, it is also possible that young-gen is not empty after full-gc, for example when the heap is too full. In this particular scenario, the old-gen might not be completely full, since the first obj in young-gen is too large to be moved there. Future small allocation, if can't satisfied by young-gen, will trigger full-gc repeatedly, because old-gen allocation is permitted only for small obj before running a GC. This can result in back-to-back full-gc. If `UseGCOverheadLimit` is disabled, some tests can timeout.

Try to relax the condition for old-gen allocation when heap is almost full. This is similar to what is covered in JDK-8346920 for Serial GC.