This is just standard log output and does not indicate that a garbage collection has taken place, though you can see GC is happening by looking at the free memory. You can monitor GC activity by directing your garbage collection output to a logfile.
For Sun JVM use -verbose:gc -Xloggc:/path/to/logs/gcout.log
For IBM JVM use -Xverbosegclog:/path/to/gclog
There are additional arguments for GC logging. See your JVM vendor documentation. You can also monitor GC activity using an external tool like VisualGC.
The logs above is generated by PRPC's Master Agent which wakes up every 10 mins (by default) to log health information about your JVM. To achieve this PRPC system code relies on the underlying Platform MXBeans. These log messages are INFO (informational) and causes no overhead to the application.