When Virtual Is Better Than Real
HOTOS '01 Proceedings of the Eighth Workshop on Hot Topics in Operating Systems
Hardware support for spin management in overcommitted virtual machines
Proceedings of the 15th international conference on Parallel architectures and compilation techniques
Towards scalable multiprocessor virtual machines
VM'04 Proceedings of the 3rd conference on Virtual Machine Research And Technology Symposium - Volume 3
Is co-scheduling too expensive for SMP VMs?
Proceedings of the sixth conference on Computer systems
Dynamic adaptive scheduling for virtual machines
Proceedings of the 20th international symposium on High performance distributed computing
Preemption adaptivity in time-published queue-based spin locks
HiPC'05 Proceedings of the 12th international conference on High Performance Computing
Lock-Visor: An Efficient Transitory Co-scheduling for MP Guest
ICPP '12 Proceedings of the 2012 41st International Conference on Parallel Processing
The Journal of Supercomputing
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When executing inside a virtual machine environment, OS level synchronization primitives are faced with significant challenges due to the scheduling behavior of the underlying virtual machine monitor. Operations that are ensured to last only a short amount of time on real hardware, are capable of taking considerably longer when running virtualized. This change in assumptions has significant impact when an OS is executing inside a critical region that is protected by a spinlock. The interaction between OS level spinlocks and VMM scheduling is known as the Lock Holder Preemption problem and has a significant impact on overall VM performance. However, with the use of ticket locks instead of generic spinlocks, virtual environments must also contend with waiters being preempted before they are able to acquire the lock. This has the effect of blocking access to a lock, even if the lock itself is available. We identify this scenario as the Lock Waiter Preemption problem. In order to solve both problems we introduce Preemptable Ticket spinlocks, a new locking primitive that is designed to enable a VM to always make forward progress by relaxing the ordering guarantees offered by ticket locks. We show that the use of Preemptable Ticket spinlocks improves VM performance by 5.32X on average, when running on a non paravirtual VMM, and by 7.91X when running on a VMM that supports a paravirtual locking interface, when executing a set of microbenchmarks as well as a realistic e-commerce benchmark.