Threaded Prefetching: A New Instruction Memory Hierarchy for Real-TimeSystems

  • Authors:
  • Minsuk Lee;Sang Lyul Min;Heonshik Shin;Chong Sang Kim;Chang Yun Park

  • Affiliations:
  • Dept. of Computer Engineering, Hansung University, 389 Samsun-dong 2 ga, Sungbook-gu, Seoul, 136-792, Korea. E-mail: mslee@ice.hansung.ac.kr;Dept. of Computer Engineering, Seoul National University, San 56-1 Shinlim-dong, Kwanak-gu, Seoul, 151-742, Korea. E-mail: symin@dandelion.snu.ac.kr;Dept. of Computer Engineering, Seoul National University, San 56-1 Shinlim-dong, Kwanak-gu, Seoul, 151-742, Korea. E-mail: symin@dandelion.snu.ac.kr;Dept. of Computer Engineering, Seoul National University, San 56-1 Shinlim-dong, Kwanak-gu, Seoul, 151-742, Korea. E-mail: symin@dandelion.snu.ac.kr;Dept. of Computer Engineering, Chung-Ang University, 221 Heuksok-dong, Dongjak-gu, Seoul, 156-756, Korea. E-mail: cypark@net1.cse.cau.ac.kr

  • Venue:
  • Real-Time Systems
  • Year:
  • 1997

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Abstract

Cache memories have been extensively used to bridge the speed gap betweenhigh speed processors and relatively slow main memory. However, they are notwidely used in real-time systems due to their unpredictable performance. Thispaper proposes an instruction prefetching scheme called threaded prefetchingas an alternative to instruction caching in real-time systems. In theproposed threaded prefetching, an instruction block pointer called a threadis assigned to each instruction memory block and is made to point to the nextblock on the worst case execution path that is determined by a compile-timeanalysis. Also, the thread is not updated throughout the entire programexecution to guarantee predictability. This paper also compares the worstcase performances of various previous instruction prefetching schemes withthat of the proposed threaded prefetching. By analyzing several benchmarkprograms, we show that the worst case performance of the proposed scheme issignificantly better than those of previous instruction prefetching schemes.The results also show that when the block size is large enough the worst caseperformance of the proposed threaded prefetching scheme is almost as good asthat of an instruction cache with 100 % hit ratio.