Sunday, May 23, 2010

KAR 0.2

I've just released an updated version of KAR, the kstat activity reporter, and a matching JKstat update.

This version carries on with the original aim of simply saving all the kstats and processing them at point of use, rather than trying to predict which output might be useful at the start.

Originally, I was using kstat -p output, and I've had to move on from that. There were a couple of minor issues with the kstat -p output that I ended up having to fix. The major one was that the times from IO kstats were converted from nanoseconds into floating-point seconds. I had a quick look to see if I could supply a modified kstat, but the conversion takes place deep inside perl - it's not just a simple presentation tweak. I could have written special-case parsing code, but it's easier and more reliable to simple generate the correct data in the first place. (Simply printing kstats is pretty trivial to code, so I did.) Having fixed that, I made a couple of other minor changes to make the output more complete (including the kstat type) and smaller and quicker to parse (eliminating all duplicates of the name of the kstat).

The overhead of running kar is reduced. The storage requirement is halved from the first version, and the cpu for a data collection is cut from over 0.2s to about 0.01s on my machine. Which is all good - you want to minimise the perturbation on the system caused by any monitoring.

I added a little sar output emulator. Just to prove that I could, printing out the cpu utilization like the default sar output. The more interesting one was to generate iostat output, which is what led me to create a custom data collector. Of course, now that I have a complete set of kstats to munge, most of the stat tools in Solaris could be replicated to show what they would have looked like over time (albeit at fairly low time resolution). And, once the CLI tools are exhausted, generation of graphs is next on the list.


jamesd_wi said...

Peter your KAR and JKstat links are broken

Peter Tribble said...

Ugh. The perils of cutting and pasting. Links fixed, and thanks for the heads up.