Evaluation of strategies to reduce the impact of machine reclaim in cycle-stealing environments

Abstract

We investigate the scheduling problem that arises in parallel applications executing on a network of machines by using a mode of cycle-stealing. In this mode of execution a parallel application executes its tasks in several machines whenever they are idle. When the user reclaims the machine, tasks must relinquish control immediately. In this case, the parallel application has the risk of losing work in progress on reclaimed machines and, therefore, the total execution time of the parallel application will be affected by the need for rescheduling the pre-empted task. We first evaluate the impact on the performance of an application when it runs on two different scenarios: a set of N dedicated machines, and a set of N non-dedicated machines (in which pre-emption may occur). This study shows that losing machines may have a considerable impact on the execution time of the application and therefore, we propose and evaluate three simple strategies to alleviate this problem. All strategies are based on the use of additional machines, but they differ in the way that these extra machines are used. In the first strategy additional machines are added to the common pool of machines used by the application. The other two are based on task replication, in which the additional machines are used to execute certain tasks that are already running in other machines.