OPTIMIZING THE JAVA VIRTUAL MACHINE INSTRUCTION SET BY ...

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ences in background processes, memory management, process scheduling
and disk performance to be ignored.
Category 2: All benchmarks that showed a general slowing trend (bars
in the histogram become higher) as the number of despecializations performed
increases were included in this category. Any benchmark that met
this criteria was placed is this category including both those benchmarks
that showed a decrease in performance as each set of despecializations was
applied and those benchmarks that only showed a performance loss when
the later despecializations were performed.
Category 3: Any benchmark that did not meet the criteria for either
Category 1 or Category 2 was placed in this category. This category was
divided into 4 sub-categories as described in section 5.2.4.
Table 5.3 presents the performance results observed for each virtual machine
tested. The number of benchmarks residing in each of the categories described previously
is reported. Summary results are included at the right side of the table
including a count of the total number of benchmarks in each category across all
benchmarks. The final column expresses these values as a percentage of all of the
benchmarks considered during testing. As the bottom row in the table indicates, it
was necessary to omit 6 benchmarks from consideration. These benchmarks included
5 benchmarks tested using IBM’s Jikes RVM on the Pentium 4 (JGF Series, JGF
Euler, JGF MolDyn, JGF RayTracer and 227 mtrt) and 1 benchmark tested using
IBM’s Jikes RVM on the Pentium III (JGF MonteCarlo). In five cases, these benchmarks
were omitted from consideration because error messages were generated during
the execution of the benchmark which indicated that the result of the benchmark’s
computation was not valid. The final benchmark was excluded because it showed
widely varying run times even in its original unmodified form. As a result, timing results
could not be used to measure the impact the impact despecialization had on the
benchmark’s runtime because variation in the run times within each test condition
was far larger than the anticipated change in performance across test conditions.
5.2.2 Category 1: Benchmarks that Show Little Difference
In Performance
Examining the data presented in Figures 5.2 through 5.9 reveals that the majority
of the benchmarks tested during this study fall into this category, showing little