[oclug] Monitoring memory usage

[Stephen M. Webb]

On 21/02/05 04:10 pm, Mark wrote:
> I am trying to figure out how much memory a process is really using (in
> this case tomcat). I tried ps and top, they give me different numbers.
>
> Here is what top says:
>   PID USER     PRI  NI  SIZE  RSS SHARE STAT %CPU %MEM   TIME CPU COMMAND
> 23691 root      25   0 37584  36M 11300 S     0.0  1.8   0:06   0 java
>
>
> Here is what "ps vgax" says:
>   PID TTY      STAT   TIME  MAJFL   TRS   DRS  RSS %MEM COMMAND
> 23691 ?        S      0:06   3383    55 456676 37580  1.8
> /usr/java/jdk/bin/java ...bla...

Those numbers look remarkably identical.  37580 vs. 37584 vs. 36M, I can't see 
the difference, can you see the difference?   You're not even going to swap 
(must be an older kernel).

> Tomcat it self says the following (getting it from the Java-VM):
> JVM
> Free memory: 5.09 MB Total memory: 11.62 MB Max memory: 254.06 MB
>
> So what is true now?
> [...]
> But the 36MB of top vs. the 12MB tomcat reports is a little too inaccurate.
> I didnt think that the java VM had that much overhead?!

Well, now you know.

Seriously, 24 M doesn't sound unreasonable for JVM overhead to me.

--
Stephen M. Webb
stephen.webb at bregmasoft.com