Hello James, On Wed, Feb 12, 2020, 6:10 AM James H. H. Lampert <jam...@touchtonecorp.com> wrote:
> Ladies and Gentlemen: > > We have a customer installation in which the JVM job for our Tomcat > server is frequently using massive amounts of CPU. > > It's Tomcat 7.0.67, running on an AS/400, in a 64-bit Java 7 JVM, with > -Xms3096m and -Xmx5120m JVM arguments. > Is this a snippet from GC log or collected data? > > GC information on the JVM job shows: > > Garbage collected heap: > > Initial heap size . . . . . . . . . : 3096.000M > > Maximum heap size . . . . . . . . . : 5120.000M > > Current heap size . . . . . . . . . : 4458.562M > > Heap in use . . . . . . . . . . . . : 1907.673M > If I am reading it correctly, actual heap usage was lower than the initial heap size. JVM still got ~3GB space left for it's use. I am not seeing any reason for JVM to do frequent GC unless heap is fragmented and unusable to JVM. > Other memory: > > Internal (break) memory size . . . . : 504.982M > > JIT memory size . . . . . . . . . . : 74.000M > > Shared classes memory size . . . . . : 0.000M > > General GC information: > > Current GC cycle . . . . . . . . . . : 2184 > > GC policy type . . . . . . . . . . . : GENCON > Is this J9 JVM? Hotspot vms do not have that GC policy. > Current GC cycle time . . . . . . . : 552 > Accumulated GC time . . . . . . . . : 5108241 > Are those values are in Millisecond or second? If in MS, on avg 2.3 sec(5108241/2184) is the collection time, which is bit high. But I don't know anything about the application. Also I don't know if there were sudden spikes which might have skewed the avg. > > It seems to be doing a lot of garbage-collecting. > > Would switching to Java 8 help? Would switching to 7.0.93 help? > I will suggest to analyze the garbage collection logs thoroughly before making such decisions. You can share it with us. Upgrade to Java 8 has some effort as Permgen was removed and Metaspace was introduced which now runs on native memory. So some testing needs to be done to make sure app is not leaking in Metaspace. > > -- > James H. H. Lampert > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org > >
