Improved Garbage Collection performance

Bryce McKinlay bryce@mckinlay.net.nz
Wed Dec 3 22:58:00 GMT 2003


On Nov 19, 2003, at 5:42 PM, John Neil wrote:

> Following a post from Jeff Sturm, I tried two relatively simple
> modifications to gcj and boehm garbage collection and was able to gain 
> a
> 200-300% improvement on a full garbage collection (from ~150ms to 
> ~50ms).

Wow - this suggests that this optimization will go a long way towards 
closing the GC-performance gap we seem to have compared to recent 
hotspot VMs.

Incidentally, I recently stumbled across this "real world", 
allocation-intensive app which performs poorly with GCJ relative to JRE 
1.4.2:

http://www.bmsi.com/java/CN2.java

You also need these input files:

http://www.bmsi.com/java/soya.att
http://www.bmsi.com/java/soya.exs

It runs nearly twice as fast under the Sun VM. However, setting 
GC_INITIAL_HEAP_SIZE to even a modest amount such as 4MB increases its 
performance dramatically (although still a bit slower than the JRE). I 
wonder if there is also a case for tweaking the heap expansion 
heuristics?

Regards

Bryce.




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