We propose a method to reuse unmodified device drivers and to improve system dependability using virtual machines. We run the unmodified device driver, with its original operating system, in a virtual machine. This approach enables extensive reuse of existing and unmodified drivers, independent of the OS or device vendor, significantly reducing the barrier to building new OS endeavors. By allowing distinct device drivers to reside in separate virtual machines, this technique isolates faults caused by defective or malicious drivers, thus improving a system’s dependability. We show that our technique requires minimal support infrastructure and provides strong fault isolation. Our prototype’s network performance is within 3–8 % of a native Linux system. Each additional virtual machine increases the CPU utilization by about 0.12%. We have successfully reused a wide variety of unmodified Linux network, disk, and PCI device drivers. 1

Quickly transmitting large datasets in the context of distributed computing on wide area networks can be achieved by compressing data before transmission. However, such an approach is not efficient when dealing with higher speed networks. Indeed, the time to compress a large file and to send it is greater than the time to send the uncompressed file. In this paper, we explore and enhance an algorithm that allows us to overlap communications with compression and to automatically adapt the compression effort to currently available network and processor resources. 1

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The performance of memory-intensive applications tends to be poor due to the high overhead added by the swapping mechanism. The same problem may be found in highly-loaded multi-programming systems where all running applications have to use the swap space in order to be able to execute at the same time. In this paper, we present a solution to these problems. The idea consists of compressing the swapped pages and keeping them in a swap cache whenever possible. The idea of a compressed swap cache was proposed a few years ago, but it did not achieve the expected results due to hardware limitations. As processors are much faster and the performance gap between processors and disk is also much bigger, we believe that now it is the right time to revisit this idea. In this paper, we present a new implementation of the compressed cache, plus some enhancements that significantly improve the performance of the swapping mechanism. Copyright © 2000 John Wiley & Sons, Ltd. KEY WORDS: compressed cache; swap mechanism; virtual memory; out-of-core applications

Cache and memory compression systems have been developed for improving memory system performance of high-performance parallel computers. Cache compression systems can reduce onchip cache miss rate and off-chip memory traffic by storing and transferring cache lines in compressed form, while memory compression systems can expand main memory capacity by storing memory pages in compressed form. However, these systems have not been quantitatively evaluated on an identical condition, making it difficult to understand the performance of a new system relative to the existing systems. In this paper, we provide an identical execution-driven simulation environment for these systems. To the best of our knowledge, none has been evaluated the performance of cache and memory compression systems by using an execution-driven simulator. Experimental results show that cache compression systems reduce cache miss rate by 16 % and memory traffic by 30%, while it expands memory capacity by less than 160%. The results also show that memory compression systems significantly expand memory capacity by over 270%. Based on these experimental analyses, we finally provide future research directions on the compression systems.

In this paper, we reevaluate the use of adaptive compressed caching in order to improve system performance through reduction of accesses to the backing stores. We propose a new and simple adaptability policy that adjusts the compressed cache size on-the-fly, and evaluate a compressed caching system with this policy through an implementation in a widely used operating system, Linux. We also redesign compressed caching in order to provide performance improvements for all tested workloads and address the problems faced in previous works and implementations that led to non-conclusive results. Among these fundamental modifications, our compressed cache is the first one to also compress file cache pages, to adaptively disable compression of clean pages when necessary and to address applications with poor compressibility. We tested a system with our adaptive compressed cache under many applications and benchmarks, each one with different memory pressures. The results showed performance improvements (up to 171.4%) in all of them if under memory pressure, and minimal overhead (up to 0.39%) when there is very light memory pressure. We believe this work shows that this adaptive compressed cache design should be actually considered as an effective mechanism for improvement in system performance. 1.

Many applications with large data spaces that cannot run on a typical workstation (due to page faults) call for techniques to expand the effective memory size. One such technique is memory compression.

Device drivers constitute a significant portion of an operating system’s source code. The effort to develop a new driver set is a sobering hurdle to the pursuit of novel operating system ventures. A practical solution is to reuse drivers, but this can contradict design goals in a new operating system. We offer a new approach to device-driver reuse, with a focus on promoting novel operating-system construction, which insulates the new operating system from the invariants of the reused drivers, while also addressing development effort. Our solution runs the drivers along with their original operating systems inside virtual machines, with some minor reuse infrastructure added to the driver’s operating system to interface with the rest of the system. This approach turns the drivers into de-privileged applications of the new operating system, which separates their architectures and reduces cross-influences, and improves system dependability. Virtual machines help reuse drivers, but they also penalize performance. The known solution for improving virtual machine performance, para-virtualization, modifies the operating system to run on a hypervisor, which has an enormous cost:

Since large-scale and data-intensive applications have been widely deployed, there is a growing demand for high-performance storage systems to support data-intensive applications. Compared with traditional storage systems, next-generation systems will embrace dedicated processor to reduce computational load of host machines and will have hybrid combinations of different storage devices. We present a new architecture of active storage system, which leverage the computational power of the dedicated processor, and show how it utilizes the multi-core processor and offloads the computation from the host machine. We then solve the challenge of applying the active storage node to cooperate with the other nodes in the cluster environment by design a pipeline-parallel processing pattern and report the effectiveness of the mechanism. In order to evaluate the design, an open-source bioinformatics application is extended based on the pipeline-parallel mechanism. We also explore the hybrid configuration of storage devices within the active storage. The advent of flash-memory-based solid state disk has become a critical role in revolutionizing the storage world. However, instead of simply replacing the traditional magnetic harddisk with thesolid state disk, researchers believe that finding a complementary approach to corporate both of