Xenrelay: An Efficient Data Transmitting Approach for Tracing Guest Domain

As the degree of virtualization is growing considerably, improving performance of virtual machine environments motivates deeper investigation of the internal processes and performance implications of virtualization. Several tools are currently available to help analyze performance in virtual machine environments. However, all of these cannot support users to add their own trace information. In this paper, we present Xenrelay, a unified, efficient, and simple mechanism for transferring large amounts of data from guest domain kernel to privileged domain user-space. Xenrelay allows users (who trace subsystems of guest domain to analyze performance) to record and fast relay data between domains. We provide a case of Xenrelay´s value in revealing behavior of virtualization. We build a block trace toolkit (using Xenrelay as an engine). This toolkit is used to track the block I/O virtualization procedures and evaluates overheads in the Xen environment. Our trace results identify that the main delay is the time of request transmission and block device operation. Besides, the results reveal impact of the I/O schedules on the disk performance.