High static power dissipation is one of the largest hurdles in the widespread adoption of on-chip optical networks. There are numerous proposals in literature for the reduction of static power by predicting the activity in future time intervals, and then powering off the laser, and also by sharing optical bandwidth. We propose a novel scheme called ColdBus in this paper that introduces a new method of predicting the optical NoC traffic using program counter addresses, moreover, we then propose novel structures and predictors for handling mispredictions. These units allow optical transmitters to share bandwidth between them while simultaneously minimizing static power. We show that ColdBus consumes 4.1X less optical power than other state of the art proposals. It additionally has a speedup of 3.1%, and improves ED2 by 18% for a suite of Splash, Parsec, and Parboil benchmarks.

Virtual-machine images are currently distributed as disk-image files, which are files that mirror the content of disks. This format is convenient for the virtual machine monitors that execute these images. However, it is not well-suited for administering images because storing images as disk-image files forces administrators to maintain the software on images with the same tools that they use to maintain the software on machines. Already, these tools cannot cope with physical server sprawl; in the future, because images can be snapshotted and cloned easily, enterprises that migrate from machines to images will need tools that scale to cope with the larger problem of virtual-machine image sprawl.To address this problem, this paper proposes the Mirage image format (MIF), a new storage format that exposes the rich semantic information currently buried in disk-image files. Disk-image files contain a mapping from file name to file content (and file metadata). MIF decouples this mapping into a manifest that maps file names to content descriptors (and file metadata) and a store that holds the content. Each image has its own manifest and a store may contain content for many images. As with disk-image files, images in MIF fully encapsulate application state including all software dependences. In addition, conversion between MIF and traditional disk-image formats is easy.This paper shows, through examples, that MIF makes some typical software management tasks--inventory control, customized deployment, and image update--faster and easier. The general technique is to operate on manifests instead of on content whenever possible. These tasks can be performed without starting images and, because manifests are simpler and orders of magnitude smaller than disk-image files, without accessing large amounts of data.

Power management in data centers has become an increasingly important concern. Large server installations are designed to handle peak load, which may be significantly larger than in off-peak conditions. The increasing cost of energy consumption and cooling incurred in farms of high-performance Web servers make low-power operation during off-peak hours desirable. This paper investigates adaptive algorithms for dynamic voltage scaling in QoS-enabled Web servers to minimize energy consumption subject to service delay constraints. We implement these algorithms inside the Linux kernel. The instrumented kernel supports multiple client classes with per-class deadlines. Energy consumption is minimized by using a feedback loop that regulates frequency and voltage levels to keep the synthetic utilization around the aperiodic schedulability bound derived in an earlier publication. Enforcing the bound ensures that deadlines are met. Our evaluation of an Apache server running on the modifier Linux kernel shows that non-trivial off-peak energy savings are possible without sacrificing timeliness.