longer ParNew collection in JDK8?

[Joy Xiong]

Hi Jon,
The graph showing ParNew pauses are as attached. Yes, it has a similar shape as the occupancy in the different ages. What experiments would you like me to try? I don't have experimental set up at hand, but I may be able to try some tests on prod machines.
The logs are as attached in the previous email.
thanks,-Joy 

     On Wednesday, February 4, 2015 10:34 AM, Joy Xiong <joyxiong at yahoo.com> wrote:
   

 It seems the files are too big. Let me try with compressed version 

     On Wednesday, February 4, 2015 10:25 AM, Joy Xiong <joyxiong at yahoo.com> wrote:
   

 Hi Jon,
The graph showing ParNew pauses are as attached. Yes, it has a similar shape as the occupancy in the different ages. What experiments would you like me to try? I don't have experimental set up at hand, but I may be able to try some tests on prod machines.
The logs are as attached.
thanks,-Joy 

     On Wednesday, February 4, 2015 8:41 AM, Jon Masamitsu <jon.masamitsu at oracle.com> wrote:
   

  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> 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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