[gclist] ratio of heap size to live data?

[William D Clinger]

In Larceny, the ratio of heap size to live data is the primary policy
parameter for the garbage collectors.  This parameter can be specified
on the command line.  For Larceny's copying collectors, the usual range
of this parameter is 2.25 to 3.0.  Larceny's copying collectors try to
interpret this parameter as an upper bound, so they often do not touch
as much heap storage as this parameter would allow.

Here are a few examples from a draft of Lars Hansen's forthcoming (late
November) PhD thesis.  All of these numbers are for Larceny's
two-generational copying collector.  His thesis will contain numbers
for seven other collectors, and for more benchmarks and parameter
settings.

  benchmark    reachable     touched       heap/        command-line   GC time
              (peak, Mby)   (peak, Mby)    reachable    parameter     (CPU sec)

  5earley12        13.5
                               20.5          1.5           2.25          5.06
                               26.5          2.0           2.5           3.95
                               35.5          2.6           2.75          3.69
                               26.5          2.0           3.0           3.37
  gcbench5         16.8
                               28.0          1.7           2.25         34.13
                               32.5          1.9           2.5          26.33
                               35.5          2.1           2.75         22.28
                               38.5          2.3           3.0          20.36
  gcold1,0         26.5
                               47.0          1.8           2.25         18.07
                               52.0          2.0           2.5          11.82
                               57.5          2.2           2.75         10.52
                               62.0          2.3           3.0           8.87
  5nboyer3         13.0
                               27.5          2.1           2.25         16.50
                               30.0          2.3           2.5          12.83
                               33.5          2.6           2.75         11.13
                               26.5          2.0           3.0          10.26
  perm25,8         11.5
                               24.0          2.1           2.25         14.02
                               27.5          2.4           2.5          11.52
                               33.5          2.9           2.75          9.75
                               31.0          2.7           3.0           8.81
  twobitlong        7.9
                               17.5          2.2           2.25          5.01
                               19.5          2.5           2.5           4.65
                               21.0          2.7           2.75          4.92
                               23.0          2.9           3.0           4.57

Will