[hobbit] vmstat graphing with CPU io wait

[Henrik Stoerner]

On Tue, Jan 25, 2005 at 08:27:37AM -0500, Tom Georgoulias wrote:
> Henrik Storner wrote:
> 
> >Where do you get the I/O wait information from ?
> 
> On RHEL3 (procps-2.0.17-10), there is a value for it in column 14 of 
> vmstat's output, labeled "wa" under "cpu"

Aha! So that's it - I had been wondering a bit why my load graphs
didn't always add up to 100% !

This is quite interesting, and definitely something that should be
tracked. So I hope you don't mind that I've tried adding it myself ...

One annoying bit with the RRD files is that changing the dataset
(e.g. adding an extra variable) is not possible. So adding the
cpu_wait data will break any existing vmstat data that has been
collected. So if we're gonna break the vmstat RRD layout for Linux
clients, we might as well do it now before the official release.  And
that should also include getting the very old layout (the one from
Linux 2.2 kernels, with the "r b w" proces-counts) aligned with the
new layout - effectively creating a single vmstat RRD format
regardless of what Linux version you are running.

So: I've modified the Linux vmstat RRD layout to always include the
"cpu_w" (from the very old vmstat version) and "cpu_wait" columns
(from the latest vmstat versions). If the client doesn't report a
value for these, they are set to the special RRD-value "undefined". So
when someone upgrades a system from Linux 2.2. to 2.4, or from 2.4 to
2.6, the vmstat data will still work.

I've also defined a "vmstat1" graph similar to the normal "vmstat"
graph, but with the cpu_wait data added (it stacks on top of the
"system" time, below "user" time).

Some sample graphs (they don't have any data yet, so you're probably
better off waiting a couple of hours before you view them):


Linux 2.6 host:
http://www.hswn.dk/hobbit-cgi/hobbitgraph.sh?host=voodoo.hswn.dk&service=vmstat1&graph=hourly

Linux 2.4 host:
http://www.hswn.dk/hobbit-cgi/hobbitgraph.sh?host=tyge.sslug.dk&service=vmstat1&graph=hourly

Linux 2.2 host (actually 2.4, but an old vmstat version):
http://www.hswn.dk/hobbit-cgi/hobbitgraph.sh?host=fenris.hswn.dk&service=vmstat1&graph=hourly


Henrik