G1:long remark pauses

Thomas Viessmann thomas.viessmann at oracle.com
Fri May 16 12:01:42 UTC 2014


Hi Bengt,


Thanks for confirming. ParallelOld had stop pauses in the range of 20 to 
30 seconds.
CMS was a disaster due to extreme fragmentation and high promotion rate 
even with
huge eden and survivors. There are definitely lots of references. I can 
find out
details.

Thanks and Regards

Thomas



On 05/16/14 13:53, Bengt Rutisson wrote:
>
> Hi again Thomas,
>
>
> On 2014-05-16 13:34, Thomas Viessmann wrote:
>> 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?
>
>
> How many reference objects does the application use? Can you run it 
> with -XX:+PrintReferenceGC to see how many there are?
>
> If there are a lot of them I don't think there is much more that can 
> be done for the remark phase. But if there are not that many I guess 
> it means that the remark phase is inefficient.
>
> Have you tried any of the other GCs? How do they behave with this 
> application?
>
> Thanks,
> Bengt
>
>
>>
>> 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
>>>>
>>>> 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.
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>>>>
>>>> ------------------------------------------------------------------------
>>>> ------------------------------------------------------------------------
>>>> Green Oracle <http://www.oracle.com/commitment> Oracle is committed 
>>>> to developing practices and products that help protect the environment
>>>
>>
>> -- 
>> 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
>

-- 
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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