1. A system comprising: a processor programmed to initiate executable operations comprising: defining a symmetric heap comprising a symmetric partition for each process of a partitioned global address space (PGAS) system; wherein each symmetric partition of the symmetric heap begins at a same starting virtual memory address and has a same global symmetric break; configuring one process of a plurality of processes of the PGAS system as an allocator process that controls allocation of blocks of memory for each symmetric partition of the symmetric heap; and maintaining, by the allocator process, isomorphic fragmentation among the symmetric partitions of the symmetric heap.