A Performance Optimization Mechanism for SSD in Virtualized Environment

摘要

Applications in the cloud computing era have the emergent requirement of fast I/O support. Compared with a hard drive disk, a solid state disk (SSD) has low delay, low energy consumption, high throughput and other advantages. However, the semantics of an SSD cannot be recognized by current virtual machine monitors. The trim instruction, which plays an important role in space management of an SSD, cannot be passed to the underlying SSD device in a virtualized environment. So, how to bridge the semantics gap between the application layer and virtualization layer for SSD devices should be an important problem. We propose Vtrim to solve the above problem in this paper. Vtrim monitors the operations in the virtual machine and sends the SSD semantics to the Domain 0 immediately. And then the semantics are translated into the operations of Domain 0, which can trigger the SSD's local instructions. To improve the write performance in multiple guest operating systems, we set a Vtrim cache to buffer all instructions from the guests and flush them into an SSD in a well-scheduled way. Experiment results in the para-virtualization environments with Vtrim show that the random write performance is improved by even up to 100% and the average response time is reduced by up to 40%.