An OpenCL framework for heterogeneous multicores with local memory

  • Authors:

  • Jaejin Lee;Jungwon Kim;Sangmin Seo;Seungkyun Kim;Jungho Park;Honggyu Kim;Thanh Tuan Dao;Yongjin Cho;Sung Jong Seo;Seung Hak Lee;Seung Mo Cho;Hyo Jung Song;Sang-Bum Suh;Jong-Deok Choi

  • Affiliations:

  • Seoul National University, Seoul, South Korea;Seoul National University, Seoul, South Korea;Seoul National University, Seoul, South Korea;Seoul National University, Seoul, South Korea;Seoul National University, Seoul, South Korea;Seoul National University, Seoul, South Korea;Seoul National University, Seoul, South Korea;Seoul National University, Seoul, South Korea;Samsung Electronics, Yongin-si, South Korea;Samsung Electronics, Yongin-si, South Korea;Samsung Electronics, Yongin-si, South Korea;Samsung Electronics, Yongin-si, South Korea;Samsung Electronics, Yongin-si, South Korea;Samsung Electronics, Yongin-si, South Korea

  • Venue:
  • Proceedings of the 19th international conference on Parallel architectures and compilation techniques
  • Year:
  • 2010

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Abstract

In this paper, we present the design and implementation of an Open Computing Language (OpenCL) framework that targets heterogeneous accelerator multicore architectures with local memory. The architecture consists of a general-purpose processor core and multiple accelerator cores that typically do not have any cache. Each accelerator core, instead, has a small internal local memory. Our OpenCL runtime is based on software-managed caches and coherence protocols that guarantee OpenCL memory consistency to overcome the limited size of the local memory. To boost performance, the runtime relies on three source-code transformation techniques, work-item coalescing, web-based variable expansion and preload-poststore buffering, performed by our OpenCL C source-to-source translator. Work-item coalescing is a procedure to serialize multiple SPMD-like tasks that execute concurrently in the presence of barriers and to sequentially run them on a single accelerator core. It requires the web-based variable expansion technique to allocate local memory for private variables. Preload-poststore buffering is a buffering technique that eliminates the overhead of software cache accesses. Together with work-item coalescing, it has a synergistic effect on boosting performance. We show the effectiveness of our OpenCL framework, evaluating its performance with a system that consists of two Cell BE processors. The experimental result shows that our approach is promising.