big project ported

Mon Oct 25 15:17:00 GMT 1999

Tom Tromey wrote:
> Jeff> Some GC profiling code would also be a great addition, to
> Jeff> measure the frequency and duration of GC, among other
> Jeff> things... I don't know if such a thing exists for the boehm
> Jeff> collector.
>> Offhand I don't know if the collector has this info. Newer versions
> might have more, though. (Upgrading is on my to-do list, still.)
> Specific suggestions for what to have would be good; we could make PRs
> for them so they wouldn't get lost.

I'd like to know:
 - how often the collector runs
 - how long (on average) the collector runs
 - how many objects (total) are allocated
 - average allocation size
...among other things. the first two are loosely reported by the
-verbosegc option of the JDK. I don't know if there are appropriate
hooks in the Boehm collector offhand. The last two measurements can be
done in libgcj proper.
At this moment I strongly suspect weaknesses in the GC. I have a JDBC
driver working under gcj now, so I can run some benchmarks against large
datasets. For small runs (<1000 rows), gcj outperforms the IBM JDK by
about 21%. For larger runs (>250000 rows), gcj is far slower than the
JDK.
Did you say you and Hans were exchanging notes about the boehm-gc
interface in libgcj? Anything interesting?
-- 
Jeff Sturm
jsturm@sigma6.com