Technologies are generally described for runtime management of processes on multicore processing systems using process affinity graphs. Two or more processes may be determined to be related when the processes share interprocess messaging traffic. These related processes may be allocated to neighboring or nearby processor cores within a multicore processor using graph theory techniques as well as communication analysis techniques to evaluate interprocess communication needs. Process affinity graphs may be established to aid in determining grouping of processors and evaluating interprocess message traffic between groups of processes. The process affinity graphs may be based upon process affinity scores determined by monitoring and analyzing interprocess messaging traffic. Process affinity graphs may further inform splitting process affinity groups from one core onto two or more cores.