[rrd-users] Re: memory graphing

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Sun Feb 11 14:22:44 MET 2001


Cody Brugh wrote:
> 
> 
> Hello,
> 
> I am graphing my memory in my box and the memory currently being used.. at
> www.codybrugh.com/~brugh14/cgi-bin/rrdscript.cgi as you can see the "memory
> being used" has went over the "actual memory in the box" Why did this
> happen?  the memory being used should never go over the line for actual RAM
> in the box.. any ideas?

You also asked:

> what one of these would I use to graph how much memory I am useing?

> enterprises.ucdavis.memory.memTotalSwap.0 = 131504
> enterprises.ucdavis.memory.memAvailSwap.0 = 131504
> enterprises.ucdavis.memory.memTotalReal.0 = 192872
> enterprises.ucdavis.memory.memAvailReal.0 = 88588
> enterprises.ucdavis.memory.memTotalFree.0 = 220092
> enterprises.ucdavis.memory.memMinimumSwap.0 = 16000

Apart from the real memory in your machine, you can also use virtual
memory. This is called swap.  It is a bit more complicated than I'm
going to describe here but it is sufficiently explained for this
purpose:

When you run out of memory, (parts of) programs that are not in use
at the moment are taken out of real memory and placed on disk in the
swap area.  When your computer needs those programs again, another
program is placed on the swap and the desired program is loaded back
into real memory.

Memory in use can therefore be memTotalReal.0+memTotalSwap.0 and
memory in use can be (memTotalReal.0+memTotalSwap.0)-memTotalFree.0

I don't know how UCD snmp handles this but it is common to count
the number of memory pages, size is then 512 or 1024 bytes.

If you are on a Linux system, have a look at /proc/meminfo

cheers,
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