FW: [olug] Possible error message

[Phil Brutsche]

A long time ago, in a galaxy far, far way, someone said...

> Good point, might want to periodically check the swap freespace in
> megabytes (free -m) to find out if it is ever being used.  Is this an
> accurate way to measure it's use?

It can be; if the available amount of swap is either static or changes
VERY slowly you're not pushing it very hard.  ie if you've pushed 10 or
20MB worth of stuff out to swap, but not much more, you're in good
shape.

vmstat - which reads VM statistics in real-time - is a better tool.  It
tells you the same thing as "free", but will also tell you how much was
pushed out or pulled in during the specified interval (the "si" - swap in
and "so" - swap out subheadings under the "swap" column).  The interval is
specified on the command line - "vmstat 2" outputs a new line every 2
seconds.

If you push out AND pull in 20-30 MB every couple of seconds I think it's
time for more memory, and yes I have seen that.  My boss couldn't believe
that a mail server handling 20 people would need more than 256MB RAM ;)

Note that some details are Linux specific.  The same general idea applies
to *BSD and other Unices, though.

-- 

Phil Brutsche
phil at brutsche.us