Performance Optimizations for Isolated Driver Domains
Shirole, Sushrut Madhukar
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In most of today's operating system architectures, device drivers are tightly coupled with other kernel components. In such systems, a fault caused by a malicious or faulty device driver often leads to complete system failure, thereby reducing the overall reliability of the system. Even though a majority of the operating systems provide protection mechanisms at the user level, they do not provide the same level of protection for kernel components. Using virtualization, device drivers can be executed in separate, isolated virtual machines, called driver domains. Such domains provide the same level of isolation to device drivers as operating systems provide to user level applications. Domain-based isolation has the advantage that it is compatible with existing drivers and transparent to the kernel. However, domain-based isolation incurs significant performance overhead due to the necessary interdomain communication. This thesis investigates techniques for reducing this overhead. The key idea is to replace the interrupt-based notification between domains with a spinning-based approach, thus trading CPU capacity for increased throughput. We implemented a prototype, called the Isolated Device Driver system (IDDR), which includes front-end and back-end drivers and a communication module. We evaluated the impact of our optimizations for a variety of block devices. Our results show that our solution matches or outperforms Xen's isolated driver domain in most scenarios we considered.
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