G1:long remark pauses

Bengt Rutisson bengt.rutisson at oracle.com
Fri May 16 11:18:13 UTC 2014


Hi Thomas,

On 2014-05-16 13:10, Thomas Viessmann wrote:
> Hi Bengt,
>
> Well, that's already done and it did improve things.
> argv[21]: -XX:+ParallelRefProcEnabled
> argv[22]: -XX:ParallelGCThreads=48

Sorry, I missed that.

>
> before -XX:+ParallelRefProcEnabled was set the stop times were in the range of 20 to 60 seconds.

OK. Glad it helped some. :)

> The application is a Cacao by Oracle. So they cannot change it.

Is there some way of reducing the amount of reference objects that Cacao 
uses? Does it have cache sizes or similar that can be tuned. With a JFR 
recording we might be able to figure out where the reference objects 
come from.

Thanks,
Bengt

>
> Thanks and Regards
>
> Thomas
>
>
>
>
>
>
> On 05/16/14 12:58, Bengt Rutisson wrote:
>>
>> Hi Thomas,
>>
>> It looks like the application is using a lot of Reference objects. 
>> The time spent in remark is dominated by reference processing. See 
>> the attached graph generated from the log file you sent.
>>
>> You can try to see if adding -XX:+ParallelRefProcEnabled improves the 
>> situation.
>>
>> If the customer is interested in updating their application they 
>> might want to see if they can reduce the number of 
>> java.lang.ref.Reference objects they use.
>>
>> Hths,
>> Bengt
>>
>>
>> On 2014-05-16 10:26, Thomas Viessmann wrote:
>>> Hi,
>>>
>>>
>>> I've been tuning a Java 7u51, Solaris 10, T4 system with 24G heap.
>>> My customer is not very happy with the remark pauses of  up to 2 
>>> seconds.
>>>  -XX:ParallelGCThreads=48 turned out to be the optimum. Here is the 
>>> log file
>>> which contains the java args at the top:
>>>
>>> http://aubing.de.oracle.com/gclog/gc_log_03052014.log
>>>
>>> Any idea to drive the remark stop times further down?
>>>
>>>
>>> Thanks and Regards
>>>
>>> Thomas
>>
>
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