G1:long remark pauses

Thomas Viessmann thomas.viessmann at oracle.com
Fri May 16 11:34:03 UTC 2014


Hi Bengt,

Sure, the application has lots of objects and references.
Downsizing the application has been tried The heap size of 24 g is
already at minimum. A  smaller heap gave OutOfmemory really quick.
My question was more whether the remark phases could be optimized
further. I assume this is not the case and we have reached the limitations
of G1, right?

Thanks and Regards

Thomas



On 05/16/14 13:18, Bengt Rutisson wrote:
>
> 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
>>>
>>
>> -- 
>> Oracle <http://www.oracle.com>
>> THOMAS VIESSMANN | Senior Principal Technical Support Engineer - Java
>> Phone: +498914302496 <tel:+49814302496> | Mobile: +491743005467 
>> <tel:+491743005467>
>> Oracle Customer Technical Support - Java
>>
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-- 
Oracle <http://www.oracle.com>
THOMAS VIESSMANN | Senior Principal Technical Support Engineer - Java
Phone: +498914302496 <tel:+49814302496> | Mobile: +491743005467 
<tel:+491743005467>
Oracle Customer Technical Support - Java

ORACLE Deutschland B.V. & Co. KG | Riesstr.25 | D-80992 Muenchen

ORACLE Deutschland B.V. & Co. KG
Hauptverwaltung: Riesstr. 25, D-80992 Muenchen
Registergericht: Amtsgericht Muenchen, HRA 95603
Geschäftsführere: Juergen Kunz

Komplementärin: ORACLE Deutschland Verwaltung B.V.
Hertogswetering 163/167, 3543 AS Utrecht, Niederlande
Handelsregister der Handelskammer Midden-Niederlande, Nr. 30143697
Geschäftsführer: Alexander van der Ven, Astrid Kepper, Val Maher

------------------------------------------------------------------------
------------------------------------------------------------------------
Green Oracle <http://www.oracle.com/commitment> Oracle is committed to 
developing practices and products that help protect the environment
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