G1 feedback: frantic GC cycles

Tony Printezis tony.printezis at oracle.com
Thu May 12 14:52:45 UTC 2011


On 5/4/2011 11:28 AM, Simone Bordet wrote:
>> Simone, you use 1g heap, right? Can you maybe add / set the following
>> params:
>> -Xms1g -Xmx1g -Xmn256m
>> -XX:-UseAdaptiveSizePolicy
> Disabling heap resizing, ok.

In G1 this will actually disable the automatic young gen resizing.

> Would it be possible that resizing of the young generation is way too
> aggressive in G1 ?

It might, if the behavior of the application is erratic. But what I was 
seeing in the log was way too aggressive. Also, we're currently looking 
at an issue that might be related. Can you also add +DisableExplicitGC 
just in case (this will make System.gc() noops).

>> -XX:InitiatingHeapOccupancyPercent=60
> Tony, would you mind to explain this parameter ?

It tells G1 to start a marking cycle when the heap is 60% full after a GC.

> I ask to increase my knowledge about G1 :)



> Thanks !
> Simon

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