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The most commonly used scheduling algorithm for parallel supercomputers is FCFS with backfilling, as originally introduced in the EASY scheduler. Backfilling means that short jobs are allowed to run ahead of their time provided they do not delay previously queued jobs (or at least the first queued job). However, predictions have not been incorporated into(More)
Direct device assignment enhances the performance of guest virtual machines by allowing them to communicate with I/O devices without host involvement. But even with device assignment, guests are still unable to approach bare-metal performance, because the host intercepts all interrupts, including those interrupts generated by assigned devices to signal to(More)
Cloud providers possessing large quantities of spare capacity must either incentivize clients to purchase it or suffer losses. Amazon is the first cloud provider to address this challenge, by allowing clients to bid on spare capacity and by granting resources to bidders while their bids exceed a periodically changing spot price. Amazon publicizes the spot(More)
As parallel jobs get bigger in size and finer in granularity, "system noise" is increasingly becoming a problem. In fact, fine-grained jobs on clusters with thousands of SMP nodes run faster if a processor is intentionally left idle (per node), thus enabling a separation of "system noise" from the computation. Paying a cost in average processing speed at a(More)
We describe a “cheat” attack, allowing an ordinary process to hijack any desirable percentage of the CPU cycles without requiring superuser/administrator privileges. Moreover, the nature of the attack is such that, at least in some systems, listing the active processes will erroneously show the cheating process as not using any CPU resources: the “missing”(More)
Over the next few years, a new model of buying and selling cloud computing resources will evolve. Instead of providers exclusively selling server equivalent virtual machines for relatively long periods of time (as done in today’s IaaS clouds), providers will increasingly sell individual resources (such as CPU, memory, and I/O resources) for a few seconds at(More)
The file-system API of contemporary systems makes programs vulnerable to TOCTTOU (time of check to time of use) race conditions. Existing solutions either help users to detect these problems (by pinpointing their locations in the code), or prevent the problem altogether (by modifying the kernel or its API). The latter alternative is not prevalent, and the(More)
SUMMARY We introduce a novel unsupervised approach for the organization and visualization of multidimensional data. At the heart of the method is a presentation of the full pairwise distance matrix of the data points, viewed in pseudocolor. The ordering of points is iteratively permuted in search of a linear ordering, which can be used to study embedded(More)
User estimates of job runtimes have emerged as an important component of the workload on parallel machines, and can have a significant impact on how a scheduler treats different jobs, and thus on overall performance. It is therefore highly desirable to have a good model of the relationship between parallel jobs and their associated estimates. We construct(More)
The overhead of a context switch is typically associated with multitasking, where several applications share a processor. But even if only one runnable application is present in the system and supposedly runs alone, it is still repeatedly preempted in favor of a different thread of execution, namely, the operating system that services periodic clock(More)