PMQS: Scalable Linux Scheduling for High End Servers

The Linux kernel scheduler for large SMP and NUMA systems needs to address conflicting requirements of system througput and application response times. This paper presents a pooled multiqueue scheduler (PMQS) designed for such high-end SMP and NUMA systems. PMQS is based on MQS, a multiqueue scheduler that has previously been shown to significantly improve upon the scalability of the current Linux 2.4 scheduler. Load imbalances introduced by the pooling approach are reduced by a load balancing module. The paper presents different kinds of load balancers and compares their efficacy. The performance evaluation of PMQS and the load balancer is carried out using application and microbenchmarks with mixed results. Pooling is shown to have potential for further improving MQS' performance though more work needs to be done on the load balancers.