G1 heap growth very aggressive in spite of low heap usage

Peter Schuller peter.schuller at infidyne.com
Mon Mar 22 20:53:52 UTC 2010

>> Yes, right now G1 expands the heap a bit too aggressively. It checks the
>> overall GC overhead and, if it's higher than the goal, it'd expand the heap
>> hoping that it will reach the required GC overhead (typically, the larger
>> the heap, the lower the GC overhead).
> Interesting. Looking at G1CollectorPolicy::expansion_amount(), this
> seems to be determined by average pause time ratio.

For the record, changing G1GCPercent to 100 (from the default of 10)
did indeed eliminate this behavior.

(Should this option be enabled in non-development builds so that it
can be tweaked on an out-of-the-box JVM?)

/ Peter Schuller
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