big project ported

[Jeff Sturm]

Anthony Green wrote:
> - I believe Jeff Sturm hacked the gc code to start off with a larger
>   heap size and that made a big difference for him.  Now that we have
>   system properties working, we should make a property for initializing
>   this.  Jeff, can you offer some guidance here?

Depending on how you use the heap, a larger initial heap can make a
difference, especially to avoid frequent collection.  I hacked in a call
to GC_expand_hp() in libjava/boehm.cc (_Jv_InitGC).  I used a
environment variable to set the initial size, but a Java property would
probably be more appropriate, especially now that we have compiler
support for properties.

Some GC profiling code would also be a great addition, to measure the
frequency and duration of GC, among other things... I don't know if such
a thing exists for the boehm collector.

> - I'm guess your app does lots of array accesses.  We have sub-optimal
>   runtime checking code, and the compiler is still not so smart about
>   automatically removing array checks.  If you're code is ready,
>   and it doesn't rely on them, try compiling with --no-bounds-check.

Also, for object arrays, type checking is inefficient.  This was
discussed a while back, in the ShellSort thread (I think).  Under some
circumstances the compiler can optimize away the test.  The ShellSort
program ran about 4x faster simply changing the Double[] array to an
Object[] array, IIRC...


-- 
Jeff Sturm
jsturm@sigma6.com