| Popis: |
Virtualization introduces a significant amount of overhead for I/O intensive applications running inside virtual machines (VMs). Such overhead is caused by two main sources: (1) device virtualization and (2) VM scheduling. Device virtualization causes significant CPU overhead as I/O data need to be moved across several protection boundaries. VM scheduling introduces delays to the overall I/O processing path due to the wait time of VMs' virtual CPUs in the run queue. We observe that such overhead particularly affects many applications involving piped I/O data movements, such as web servers, streaming servers, big data analytics, and storage, because the data has to be transferred first into the application from the source I/O device and then back to the sink I/O device, incurring the virtualization overhead twice. In this paper, we propose vPipe, a programmable framework to mitigate this problem for a wide range of applications running in virtualized clouds. vPipe enables direct "piping" of application I/O data from source to sink devices, either files or TCP sockets, at virtual machine monitor (VMM) level. By doing so, vPipe can avoid both device virtualization overhead and VM scheduling delays, resulting in improved I/O throughput and application performance as well as significant CPU savings. |
