A lock-aware virtual machine scheduling scheme for synchronization performance

Abstract

In virtualized environments, multiprocessor virtual machines encounter synchronization problems such as lock holder preemption (LHP) and lock waiter preemption (LWP). When the issue happens, a virtual CPU (VCPU) waiting for such locks spins for an extraordinarily long time and wastes CPU cycles seriously, resulting in a significant degradation of system performance. Recent research that addresses this issue has some shortcomings. To address these problems, this paper proposes an efficient lock-aware virtual machine scheduling scheme to avoid LHP and LWP. Our approach detects lock holders and waiters from the virtual machine monitor side, and gives preempted lock holders and waiters multiple, continuous, extra scheduling chances to release locks, assuring that the de-scheduled VCPUs are not lock holders or waiters with high probability. We implement a Xen-based prototype and evaluate the performance of lock-intensive workloads. The experimental results demonstrate that our scheduling scheme fundamentally eliminates lock holder preemptions and lock waiter preemptions.