[CentOS] CentOS server running java - won't let go of swap

Les Mikesell lesmikesell at gmail.com
Sun Mar 7 17:35:54 UTC 2010

Sean Carolan wrote:
> I'm monitoring some CentOS 5 servers running Sun Java.  We have set 
> things up so 2048 MB of RAM are available for the base operating system, 
> taking into account the xMx and permgen settings.  What we're seeing is 
> the swap space getting used up, and not released.  Is this normal 
> behavior?  Performance doesn't seem to be affected, however I'm a bit 
> concerned that the swap file is completely full:
> free -m
>              total       used       free     shared    buffers     cached
> Mem:          9993       9945         48          0        174       1695
> -/+ buffers/cache:       8074       1919
> Swap:         2047       2033         14
> Here are the xMx and permgen settings:
> -Xms7177m -Xmx7177m -XX:MaxPermSize=768m
> Apart from Java/Tomcat/Apache and some HP hardware monitoring tools we 
> are not running anything else on this server.

I think Xms/x is java's heap space for program object storage.  It doesn't take 
into account the space needed for the JVM itself.  Top should show you the 
actual memory usage - along with any other programs that might be using a lot.

   Les Mikesell
    lesmikesell at gmail.com

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