[rrd-users] rrdtool backed mrtg using massive amounts of memory

Steven Hartland killing at multiplay.co.uk
Wed May 13 03:13:20 CEST 2009

Having an issue here where mrtg which rrdtool backed in our
case is using a massive amount memory 5GB+ after a short
period of time.

The config isn't that big just 371 targets. I seem to remember
a thread a while back suspecting mmap causing an issue so
I disabled it on the off chance this would help and sure
enough the mrtg perl process is now ~500MB.

So why would mmap option cause such massive memory usage?

rrdtool version: 1.3.7
mrtg version: 2.16.2,1 
FreeBSD version: 7.0-RELEASE AMD64

Its not just memory though actual processing speeds are
massively effected. The machine this runs on does two things
mrtg network port starts and server stats read from mysql DB

With mmap enabled the a run of the server stats was taking
over 15mins without it ~1 1/2mins, so a massive difference.

The machine has only got 4GB of ram so I expect the memory
usage is seriously dragging down the speed but obviously
the end result is a major slow down when enabling an option
which should be increasing performance.

Comments, thoughts etc?


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