On the Java Posse mailing list, someone posted a question about a JVM that was eating CPU like candy from a baby.
Here's the problem from the mailing list:
I found a java process whose cpu is almost 100% at my notebook.
Here is the top output:
PID USER????? PR? NI? VIRT? RES? SHR S %CPU %MEM TIME+
6150 root????? 20?? 0 1411m 612m? 12m R 98.8 15.7? 45:49.12
and the jstack output for thread 6150(0x1806):
"VM Thread" prio=10 tid=0x0000000040ca9000 nid=0x1806 runnable
the last is jstat -gc output:
S0C??? S1C??? S0U??? S1U????? EC?????? EU??????? OC???????? OU?????? PC???? PU??? YGC???? YGCT??? FGC??? FGCT???? GCT
64.0?? 64.0?? 0.0??? 0.0?? 332992.0?? 0.0???? 666304.0?? 73192.5?? 83968.0 83967.9?? 6893?? 17.576 6882? 2705.923 2723.499
Before you read further, take a look at this and see if you can tell what the problem is...
Now for the solution. Kirk Pepperdine said this:
YGC (Young gen count) is 6893 and FGCT is 6882 which is a completely ridiculous full GC to GC ratio. As for the times, YGCT is 17.56 where as FGCT is 2705.923 giving a 99.9% Full GC to GC ratio. A normal FGC:GC ratio should be less than 5% and less than 1% is desirable.
Second observation
PC is perm gen configured @ 83968 and PU perm gen used at 83967.9
Diagnosis: Frequent Full GC's due to Perm Gen being full.
Solution: Increase the size of perm gen using -XX:MaxPermSize.