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(0×1806):
“VM Thread” prio=10 tid=0x0000000040ca9000 nid=0×1806 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.
Awesome work, Mr. Pepperdine. Kirk is a frequent speaker at conferences, and he does a lot of performance work. If I needed a performance guru, Kirk would be the first person I’d think of.