Last summer I announced that I had released a performance monitoring
tool called collectl and just wanted to let people know I've since
significantly improved the website at http://collectl.sourceforge.net/
to include examples, a block diagram and even included a couple of pages
on some interesting kernel problems it helped identify, though they've
since been addressed. Perhaps one of the more interesting ones is that
not too long ago, and I'm really not sure when it actually got fixed, it
was impossible to accurately measure network traffic at 1 second
intervals and worse, you'd periodically see double the actual rate
reported. Try it out on an older kernel and see for yourself!
However, since collectl can monitor at subsecond intervals you could
monitor those older kernels at 0.9765 seconds and see accurate data.
Rather than me try to explain it, take a look at
http://collectl.sourceforge.net/NetworkStats.html to read more.

I think a couple of other features I may not have said enough about is
monitoring Infiniband and Lustre performance, for which I don't believe
there are any good tools available. You can get IB data from asking the
switch, but you can't easily get it from the local system. There is
actually a wealth of information Lustre provides but no good tools to
mine it. Now there is. With collectl you can see a second-by-second
(or any other interval you prefer) snapshot of just what is happening to
these key resources and can even watch the load on cpu, memory and
network at the same time. If you prefer, and most people do, just run
collectl as a service and it will maintain a set of compressed rolling
logs containing 10 second samples (all customizable) and do it all at
<0.1% of system overhead.

Enough rambling already. Download it and see for yourselves...

-mark


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