NDLI: Grover: Looking for Performance Improvement by Disabling Local Memory Usage in OpenCL Kernels

Content Provider	IEEE Xplore Digital Library
Author	Jianbin Fang Sips, H. Jaaskelainen, P. Varbanescu, A.L.
Copyright Year	2014
Abstract	Due to the diversity of processor architectures and application memory access patterns, the performance impact of using local memory in OpenCL kernels has become unpredictable. For example, enabling the use of local memory for an OpenCL kernel can be beneficial for the execution on a GPU, but can lead to performance losses when running on a CPU. To address this unpredictability, we propose an empirical approach: by disabling the use of local memory in OpenCL kernels, we enable users to compare the kernel versions with and without local memory, and further choose the best performing version for a given platform. To this end, we have designed Grover, a method to automatically remove local memory usage from OpenCL kernels. In particular, we create a correspondence between the global and local memory spaces, which is used to replace local memory accesses by global memory accesses. We have implemented this scheme in the LLVM framework as a compiling pass, which automatically transforms an OpenCL kernel with local memory to a version without it. We have validated Grover with 11 applications, and found that it can successfully disable local memory usage for all of them. We have compared the kernels with and without local memory on three different processors, and found performance improvements for more than a third of the test cases after Grover disabled local memory usage. We conclude that such a compiler pass can be beneficial for performance, and, because it is fully automated, it can be used as an auto-tuning step for OpenCL kernels.
Starting Page	162
Ending Page	171
File Size	587624
Page Count	10
File Format	PDF
ISBN	9781479956180
ISSN	01903918
DOI	10.1109/ICPP.2014.25
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2014-09-09
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Indexes Kernel Equations Instruction sets Data structures Memory management Hardware Reverse Engineering OpenCL Local Memory
Content Type	Text
Resource Type	Article

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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