gcc 3.3 garbage collector defaults

[Zack Weinberg]

Ziemowit Laski <zlaski@apple.com> writes:

>
> FWIW, I believe the defaults have _not_ changed.  The 3.2.1 ggc has
> (in ggc-page.c)
>
>    #define GGC_MIN_EXPAND_FOR_GC (1.3)
>    #define GGC_MIN_LAST_ALLOCATED (4 * 1024 * 1024)
>
> whereas the 3.3 branch has (in params.def)
>
>    # define GGC_MIN_EXPAND_DEFAULT 30
>    # define GGC_MIN_HEAPSIZE_DEFAULT 4096
>
> These _seem_ to be used in a semantically equivalent fashion
> by the ggc_collect() routines in the two compilers.

cvs annotate says that the #defines in 3.2.x have not changed since
version 1.1 of ggc-page.c.  It was my intent, when I replaced the
#defines with parameters, not to change the values.

What I suspect was either that these settings were chosen without much
testing, or that they were good at the time they were chosen, but are
not so good for newer machines and/or newer compiler's allocation
thresholds.

zw