Paired Gang Scheduling

Conventional gang scheduling has the disadvantage that when processes perform I/O or blocking communication, their processors remain idle because alternative processes cannot be run independently of their own gangs. To alleviate this problem, we suggest a slight relaxation of this rule: match gangs that make heavy use of the CPU with gangs that make light use of the CPU (presumably due to I/O or communication activity), and schedule such pairs together, allowing the local scheduler on each node to select either of the two processes at any instant. As I/O-intensive gangs make light use of the CPU, this only causes a minor degradation in the service to compute-bound jobs. This degradation is more than offset by the overall improvement in system performance due to the better utilization of the resources.