Characterizing memory performance in vector multiprocessors

ABSTRACT

We propose a set of three memory performance measures directed at vector multiprocessors. One is the port reservation time which is closely related to the commonly-used memory bandwidth measure. The second is the vector fill time and is the latency through the memory system for an entire vector operation. The third is the slowest element time, which is the highest effective latency of all the elements of a vector. The three measures are sufficent to characterize the memory system's influence on the processor's usage of memory ports, functional units, and vector registers--the three main resources that determine vector performance. Simulation results for a next-generation-class vector multiprocessor are given to illustrate typical values for the measures and their inter-relationships. These results display a type of bimodal performance behavior where performance is better for both high and low vectorization levels than it is for moderate vectorization levels. The results are also used with a simple code sequence to illustrate the effect of memory system delays on chained and non-chained performance. These results suggest that chaining may be more efficient if longer vector lengths are used.

REFERENCES

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INDEX TERMS

Primary Classification:
  C. Computer Systems Organization
  C.1 PROCESSOR ARCHITECTURES
      C.1.2 Multiple Data Stream Architectures (Multiprocessors)
          Subjects: Array and vector processors

Additional Classification:
  B. Hardware
  B.3 MEMORY STRUCTURES
      B.3.3 Performance Analysis and Design Aids**
          Subjects: Simulation**

  C. Computer Systems Organization
  C.4 PERFORMANCE OF SYSTEMS
      Subjects: Performance attributes
  C.5 COMPUTER SYSTEM IMPLEMENTATION
      C.5.1 Large and Medium ("Mainframe") Computers
          Subjects: Super (very large) computers

General Terms:
Design, Measurement, Performance