longer ParNew collection in JDK8?

[Jon Masamitsu]

Joy,

Do the ParNew pauses you see have a shape similar to the occupancy
seen at the different ages?

Do you have a test setup where you can do some experiments?

Can you send a gc log from jdk8 and jdk6?  I'm not looking for anything
in particular but might see something.

Jon

On 2/3/2015 2:37 PM, Joy Xiong wrote:
> Hi Jon,
>
> The tenuring distribution looks similar to me. Pls see the attached 
> graphs, which show the occupied size in age 1, age 2, age 14 and age 
> 15 after the young GC. I have graphs showing occupied size in other 
> ages too, and they all look similar to me. Let me know you'd like to 
> have all of them.
>
> thanks,
> -Joy
>
>
> On Monday, February 2, 2015 12:46 PM, Jon Masamitsu 
> <jon.masamitsu at oracle.com> wrote:
>
>
> Joy,
>
> If you look at the tenuring distribution 
> (-XX:+PrintTenuringDistribution), do
> they look similar?
>
> Jon
>
> On 02/02/2015 10:38 AM, Joy Xiong wrote:
>> Hi Jon,
>>
>> Yes, most objects in my application die young and very little 
>> promoted. As you can see from the attached figure (the occupied heap 
>> size from Sep 28 to Nov 11), CMS happened very rare. However, it 
>> seems two releases do not have much difference in promotion rate, as 
>> they have same number of CMS in the log.
>>
>> We have the same JVM parameters for both releases as below:
>>
>> CommandLine flags: -XX:+AlwaysPreTouch 
>> -XX:CMSInitiatingOccupancyFraction=70 -XX:ErrorFile=logs/hs_err.log 
>> -XX:InitialHeapSize=34271657984 -XX:+ManagementServer 
>> -XX:MaxHeapSize=34271657984 -XX:MaxNewSize=2147483648 
>> -XX:NewSize=2147483648 -XX:OldPLABSize=16 -XX:+PrintGC 
>> -XX:+PrintGCApplicationConcurrentTime 
>> -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCDateStamps 
>> -XX:+PrintGCDetails -XX:+PrintGCTimeStamps 
>> -XX:+PrintTenuringDistribution -XX:SurvivorRatio=2 
>> -XX:+UnlockDiagnosticVMOptions -XX:+UseCompressedClassPointers 
>> -XX:+UseCompressedOops -XX:+UseConcMarkSweepGC -XX:+UseParNewGC
>>
>> thanks,
>> -Joy
>>
>>
>> On Monday, February 2, 2015 10:06 AM, Jon Masamitsu 
>> <jon.masamitsu at oracle.com> <mailto:jon.masamitsu at oracle.com> wrote:
>>
>>
>> Joy,
>>
>> Is your application such that most everything dies in the
>> young generation and very little is promoted?  If yes,
>> do you know if there is a difference in how much is
>> promoted between the two releases?
>>
>> Jon
>>
>> On 01/29/2015 10:27 AM, Joy Xiong wrote:
>>>
>>> Hi,
>>>
>>> We recently move our services from JDK6 to JDK8, but observe longer 
>>> ParNew GC pause in JDK8. For example, the pause time increase from 
>>> 27ms to 43ms in one service. The service has the JVM parameters as 
>>> below:
>>> -Xms32684m -Xmx32684m -XX:NewSize=2048m -XX:MaxNewSize=2048m 
>>> -XX:+UseConcMarkSweepGC -XX:+UseParNewGC 
>>> -XX:CMSInitiatingOccupancyFraction=70 -XX:SurvivorRatio=2 
>>> -XX:+AlwaysPreTouch -XX:+UseCompressedOops 
>>> -XX:+PrintTenuringDistribution -XX:+PrintGCDetails 
>>> -XX:+PrintGCDateStamps -Xloggc:logs/gc.log 
>>> -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCApplicationConcurrentTime
>>>
>>> Is this longer ParNew pause expected? Any suggestions to mitigate 
>>> the longer pause?
>>>
>>> thanks,
>>> -Joy
>>>
>>>
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>>
>>
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