Memory check

Ok I understand the concept.  However, I don't want to continue to receive
Alerts because Linux is doing exactly what it is designed to do.  Does
anyone have a script that can clear the buffers and stop hobbit from paging
me?  Can I modify the script to only alert when REAL memory is at 100% or
higher?  Or do I have to reboot my server ever morning to resolve this
alert?  I currently have the alerts disabled, but I am concerned that I
could miss a critical error

Dave
 

-----Original Message-----
From: hobbit-return-5584-david=user-9e293dd11111@xymon.invalid [mailto:hobbit-return-5584-david=stenhouseconsulting.com at hswn.
dk] On Behalf Of Henrik Stoerner
Sent: Wednesday, February 08, 2006 1:45 AM
To: user-ae9b8668bcde@xymon.invalid
Subject: Re: [hobbit] Memory check

On Tue, Feb 07, 2006 at 07:41:23PM -0500, David Gilmore wrote:

My hobbit server (Fedora FC4) has 1.25 gig of memory installed.  When > the server is backed, up using Retrospect client, REAL memory usage > spikes from 34% to 97% and stays at that level until a reboot.  When I > check the system performance, using the built in system monitor, user memory is at 18.9%.
Dell Open Manage is using the most memory at 3% with a few additional > processes between 1% and 2%.  Everything else is well under 1%.  What > exactly is hobbit reporting on when it says that Physical/Real memory > is at 97%, Actual memory is at 17%, and Swap is at 0%?

Hobbit reports the output from the "free" command. It probably looks somewhat like this after you've run a backup:

             total       used       free     shared    buffers cached
Mem:        646432     642172       4260          0     167676 136068
-/+ buffers/cache:     338428     308004
Swap:       511992          4     511988

The "Mem" line here tells you that there is 640 MB RAM installed, and all except 4 MB is being "used". However, a lot of that is used for "buffers" and "cache", which is the Linux kernel's dynamically resized disk cache; if an application needs more RAM that is "free", the disk cache/buffers are discarded and the memory made available to the application.

So that's why the "-/+ buffers/cache" line is interesting: This shows the used/free memory count if the buffers/cached is counted as "free"
memory. Hobbit report this as the "actual" memory count.

So a Linux system will practically always have a REAL memory usage close to 100% (Linus Torvalds once said that "unused RAM is *wasted* RAM, and there's no reason to spend lots of money on something that isn't used" - quoting from memory). The ACTUAL memory usage (should) be a lot less, and is what you'll want to keep an eye on.


Regards,
Henrik