[rhn-users] memory management on RHE3

[GREG WOJTAK]

The way I understand it (and someone please correct me if I'm wrong),
when a process launches, it allocates memory as it needs it.  When it
frees up memory either by calling free() or something equivalent, or by
exiting, the memory is marked as free by the kernel but that it does not
show up as free until the kernel needs to reallocate it again.  So,
using top or any other memory utilization tool will show that there is a
lot less free memory than there really is.

I'm sure there's a more elegant algorithm for the memory management,
but I think this is the gist of why you never see your memory free up.


Greg Wojtak
Unix Systems Administrator
Sallie Mae
(317) 598-4058

>>> dczarkowski at infinitesource.ca 5/31/2005 2:26:31 PM >>>
I have a problem with performance on RHE3 web server. Current Kernel
is
2.4.21-27.0.4.ELsmp


Free -m shows:

. total used free shared buffers cached

Mem: 5897 5839 57 0 283 4653

-/+ buffers/cache: 902 4994

Swap: 12001 0 12001


Server is running postgresql-7.3.4, jakarta-tomcat-4.1.31 and java
j2sdk1.4.2_08, apache 2 with mod_jk. There is also small ftp activity.

JVM parameters used are TOMCAT_OPTS="-Xms1640m -Xmx2048m"


When the server is rebooted, output of free shows about 500M used
memory, when tomcat is started up it only takes/commits small amount
of
memory.

After a few days however the free output is as above.


I don't know where the rest of the memory is allocated, I am not sure
how to trace what is using it. If you can not answer my questions can
you tell me where can I find resources that would help me to
troubleshoot my problems? 


DarekC



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