CentOS 5, 'usage' not accurate?

[neek]

Hi there,

I've downloaded and installed the latest, and though 'top' shows me
100% cpu usage for the java pid, the javasysmon library seems to
return a consistently low value. However, top does not report 100%
overall, so javasysmon may be doing The Right Thing and something else
is going wrong.

Please excuse this paste, I don't know how better to do this with
google groups:

top - 08:28:14 up 123 days, 4:40, 2 users, load average: 1.43,
1.70, 1.81
Tasks: 79 total, 2 running, 77 sleeping, 0 stopped, 0 zombie
Cpu(s): 3.1%us, 9.8%sy, 0.0%ni, 87.1%id, 0.0%wa, 0.0%hi,
0.0%si, 0.0%st
Mem: 786432k total, 488532k used, 297900k free, 0k
buffers
Swap: 0k total, 0k used, 0k free, 0k
cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+
COMMAND
8018 premier 20 0 324m 206m 10m S 98.2 26.9 204:25.27
java
5673 premier 15 0 2284 1048 816 R 1.0 0.1 0:00.02
top
1 root 15 0 2152 664 572 S 0.0 0.1 0:11.34
init

Note the low "user" percentage, the machine is 87.1% idle.. yet the
java process has 98.2% CPU reported on its line.

The bug in my code is my problem, but I'm trying to use javasysmon to
let me know _when_ the cpu sticks at 100%, which happens erratically
during the day and needs restarting. It's a jetty based web server,
and I start a new Thread-derived class which owns its own instance of
JavaSysMon and reports to a custom log file like this:

[usage 0.14302027] [55823304 bytes free of 101384192]
SystemMonitor: 11-03-11 08:19:24 - pid 8018 [physical total: 768Mb
free: 299Mb] [usage 0.15071768] [43454504 bytes free of 101384192]
SystemMonitor: 11-03-11 08:19:29 - pid 8018 [physical total: 768Mb
free: 299Mb] [usage 0.15027028] [46255576 bytes free of 101384192]
SystemMonitor: 11-03-11 08:19:34 - pid 8018 [physical total: 768Mb
free: 298Mb] [usage 0.16804487] [58059736 bytes free of 101384192]

the 'usage' reported is always low, 0.1 - 0.18 or so.

The pid reported by 'top' and javasysmon are consistent (8018 in the
above examples). Is there something obvious I might be doing wrong?
I don't understand how my java app can be at 100% yet top report a low
actual usage.

Thanks
Nick