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A. Pathania, V. Venkataramani, M. Shafique, T. Mitra, J. Henkel:
"Defragmentation of Tasks in Many-Core Architecture";
ACM TRANSACTIONS ON ARCHITECTURE AND CODE OPTIMIZATION, 14 (2017), 1; S. 2:1 - 2:21.

Many-cores can execute multiple multithreaded tasks in parallel. A task performs most efficiently when it is executed over a spatially connected and compact subset of cores so that performance loss due to communication overhead imposed by the task´s threads spread across the allocated cores is minimal. Over a span of time, unallocated cores can get scattered all over the many-core, creating fragments in the task mapping. These fragments can prevent efficient contiguous mapping of incoming new tasks leading to loss of performance. This problem can be alleviated by using a task defragmenter, which consolidates smaller fragments into larger fragments wherein the incoming tasks can be efficiently executed. Optimal defragmentation of a many-core is an NP-hard problem in the general case. Therefore, we simplify the original problem to a problem that can be solved optimally in polynomial time. In this work, we introduce a concept of exponentially separable mapping (ESM), which defines a set of task mapping constraints on a many-core. We prove that an ESM enforcing many-core can be defragmented optimally in polynomial time.

Many-core, task defragmentation, multiagent systems

http://dx.doi.org/10.1145/3050437