#Number
TR-PDS-1998-008

#Title
The Effects of Memory-Access Ordering on Multiple-Issue Uniprocessor Performance

#Author
Brian Grayson, Lizy John, and Craig Chase

#Abstract
We study the effect of memory access ordering policies on processor
performance.  Relaxed ordering policies increase available
instruction-level parallelism, but such policies must be evaluated
subject to their effect on memory consistency --- since virtually all
microprocessors are designed to be compatible with shared memory
multiprocessor systems, even uniprocessor desktop computers are
constrained by the rules of multiprocessor memory consistency models.

We define the set of potential parallelism-restricting ordering rules
found in strong memory models.  We then construct a spectrum of
possible memory models by progressively relaxing these restrictions.
Some of our models are similar to those of existing commercial
processors; other models illustrate potential alternatives.  We
simulate and analyze several uniprocessor benchmarks from the SPEC95
and SPLASH-2 suites using a superscalar processor simulator
(Armadillo) developed at the University of Texas at Austin.  This
simulator models dataflow instruction execution, branch prediction,
speculative execution, memory disambiguation and an aggressive memory
system.

Our experiments confirm the significant benefits of a weaker memory
model on processor performance.  Although the absolute performance
varies considerably from benchmark to benchmark, the relative
performance gains of relaxing specific memory ordering constraints is
surprisingly similar across most of the benchmarks.

#Bib
@techreport{YourBibNameHere,
  Author = "Brian Grayson and Lizy John and and Craig Chase",
  Title = "The Effects of Memory-Access Ordering on Multiple-Issue Uniprocessor Prformance",
  Number = "TR-PDS-1998-008",
  Institution = "Department of Electrical and Computer Engineering, The Universit of Texas at Austin",
  month = "July",
  year = "1998",
  note = "Available from {\tt
    http://maple.ece.utexas.edu/TechReports/1998/TR-PDS-1998-008.ps.Z}.  A
    version of this paper was presented at IPCCC 1999."
}