Strange Performance Tests

Lars Andersen lars@rimfaxe.com
Wed Jul 10 13:09:00 GMT 2002


On Wed, 2002-07-10 at 21:48, Michael Smith wrote:
> Lars Andersen wrote:
> > On Wed, 2002-07-10 at 21:21, Andrew Pinski wrote:
> > 
> >>I think the spikes in both are the gc (garbage collector) running.
> >>The gc for gcj is boehm's which might be slower than the one 
> >>used by Sun.
> >>
> >>Thanks,
> >>Andrew Pinski
> > 

> 
> try increasing the initial heap size.
> 
> For gcj,
> export GC_INITIAL_HEAP_SIZE=<size>
> 
> For the jdk,
> java -Xmx<size>
> 
> If the spikes occur less frequently, but have longer times, that would 
> be indicative of the GC.
> 


OK, the plot thickens!

I tried with following settings  of GC_INITIAL_HEAP_SIZE:

16000000, 32000000 and 128000000

GCJ now runs as fast or faster than SUN jdk1.4 regardless of what
initial heapsize I choose!

Apparently, just setting the initial heap size to something more than
doubles the performance of my app!!!

/Lars Andersen






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