June 22–26, 2014
Leipzig, Germany

Presentation Details

Name: CoreTSAR: Adaptive Worksharing for Heterogeneous Systems
Time: Tuesday, June 24, 2014
08:30 am - 09:00 am
Room:   Hall 3
CCL - Congress Center Leipzig
Breaks:07:30 am - 11:00 am Welcome Coffee
Speaker:   Tom Scogland, Virginia Tech
Abstract:   The popularity of heterogeneous computing continues to in- crease rapidly due to the high peak performance, favorable energy efficiency, and comparatively low cost of accelerators. However, heterogeneous programming models still lack the flexibility of their CPU-only counterparts. Accelerated OpenMP models, including OpenMP 4.0 and OpenACC, ease the migration code from CPUs to GPUs but lack much of OpenMP’s flexibility: OpenMP applications can run on any number of CPUs without extra user effort, but GPU implementations do not offer similar adaptive worksharing across GPUs in a node, nor do they employ a mix of CPUs and GPUs. To address these shortcomings, we present CoreTSAR, our library for scheduling cores via a task-size adapting runtime system by supporting worksharing of loop nests across arbitrary heterogeneous resources. Beyond scheduling the computational load across devices, CoreTSAR includes a memory-management system that operates based on task association, enabling the runtime to dynamically manage memory movement and task granularity. Our evaluation shows that CoreTSAR can provide nearly linear scaling to four GPUs and all cores in a node without modifying the code within the parallel region. Furthermore, CoreTSAR provides portable performance across a variety of system configurations.

Tom Scogland, Virginia Tech; Wu-Chun Feng, Virginia Tech; Barry Rountree, LLNL; Bronis de Supinski, LLNL