| Summary: | 碩士 === 國立交通大學 === 資訊科學與工程研究所 === 97 === Nowadays, quite a few embedded processors have not only caches but also a scratch-pad memory (SPM). For these processors, it is essential to explore and develop a scheme to make good use of the SPM. There is no successful SPM allocation scheme proposed previously that can adjust SPM allocation exactly according to variations in the program behavior all the time throughout program execution. Furthermore, due to the widening speed gap between cache and main memory, stall cycles resulting from instruction cache misses have become a considerable part in the program execution time. For Java applications, we observed that over half of the instruction cache misses are caused by JIT-compiled code. Therefore, we proposed a novel dynamic SPM allocation scheme for JIT-compiled code to reduce instruction cache misses, in which the SPM allocation is adjustable according to variations in the program behavior.
In our design, every method is allocated to the SPM when it is compiled by the JIT compiler. Once the SPM lacks free space, certain methods in the SPM will be reallocated to the main memory. Throughout program execution, the information about instruction cache misses caused by JIT-compiled code is gathered, and certain JIT-compiled methods in the main memory would be reallocated to the SPM according to the gathered information.
The experimental results demonstrate that not only does our design make effective use of the SPM to reduce instruction cache misses and thus improve the program execution performance for the processors that have an instruction cache and an SPM, but it also has better performance than the processors only containing caches whose costs are higher than or the same as our design.
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