CMS and Parallel GC consumes high CPU-Need Help

Question

Hi,
We are using Hot Spot 64 bit JVM(java.runtime.version=1.6.0_26-b03,java.vm.version=20.1-b02),And in production we are facing a issue with long pause time during GC.While monitoring we also observed that CPU consumption(Almost >90%) during GC was very high.
Currently we use three 8 core 32 GB RHEL server each having total of 4 JVM with following config
Box(Server) 1:
1)2 online JVM with xms=xmx=4g and xmn=1g,GC-CMS,initialoccupationfrequency=50%
2)2 batch JVM with xmx=4GB,xms=512MB,GC-parallelGC
Box(Server) 2:
1)2 online JVM with xms=xmx=4g and xmn=1g,GC-CMS,initialoccupationfrequency=50%
2)2 batch JVM with xmx=4GB,xms=512MB ,GC-parallelGC
Box(Server) 3:
1)2 online JVM with xms=xmx=4g and xmn=1g,GC-parallelGC
2)2 batch JVM with xmx=4GB,xms=512MB GC-parallelGC
We are facing similar issue in all the three servers,At first we had CMS for all the online JVM's.We suspected CMS as the reason for CPU consumption so we swapped to ParallelGC on one box but still facing the same issue.We have a dependency from an external system,if the GC is more than 60 sec the extrenal system will disconnect.thisi is hampering our daily activities a lot.This issue is occuring during less load on the system with less network utilization Can any one help on this.
My quesstions
1)How much resource normally CMS or Parallel GC consumes?
2)Does having 4 JVM in a server causes this problem?What is the optimum to have?
3)What will happen if all the four JVM triggers GC

Answer 1

Hi,
We are using Hot Spot 64 bit JVM(java.runtime.version=1.6.0_26-b03,java.vm.version=20.1-b02),And in production we are facing a issue with long pause time during GC.While monitoring we also observed that CPU consumption(Almost >90%) during GC was very high.
Currently we use three 8 core 32 GB RHEL server each having total of 4 JVM with following config
Box(Server) 1:
1)2 online JVM with xms=xmx=4g and xmn=1g,GC-CMS,initialoccupationfrequency=50%
2)2 batch JVM with xmx=4GB,xms=512MB,GC-parallelGC
Box(Server) 2:
1)2 online JVM with xms=xmx=4g and xmn=1g,GC-CMS,initialoccupationfrequency=50%
2)2 batch JVM with xmx=4GB,xms=512MB ,GC-parallelGC
Box(Server) 3:
1)2 online JVM with xms=xmx=4g and xmn=1g,GC-parallelGC
2)2 batch JVM with xmx=4GB,xms=512MB GC-parallelGC
We are facing similar issue in all the three servers,At first we had CMS for all the online JVM's.We suspected CMS as the reason for CPU consumption so we swapped to ParallelGC on one box but still facing the same issue.We have a dependency from an external system,if the GC is more than 60 sec the extrenal system will disconnect.thisi is hampering our daily activities a lot.This issue is occuring during less load on the system with less network utilization Can any one help on this.
My quesstions
1)How much resource normally CMS or Parallel GC consumes?
2)Does having 4 JVM in a server causes this problem?What is the optimum to have?
3)What will happen if all the four JVM triggers GC