nmon - I can't see all the CPUs on-screen. Please Help! (AIXpert Blog)

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nmon - I can't see all the CPUs on-screen. Please Help!

nagger Visits (18570)

Here is another question from that larger Power 7 machine customer. They have large Virtual Machines (Logical Partitions) and can't see all the CPUs on the screen. This is made worst by Power 7 machines - not a problem with the processors or machines but there are:

So many CPUs on larger machines like Power 770/780 and the mighty Power 795
Then the new Simultaneous Multi-Threading (SMT) now means four threads per physical CPU (core).

This means lots of physical CPUs and each has four logical CPUs. So what happens on the screen - you see a warning like this "Warning: Some Statistics may not be shown":

If you have 64 CPUs in your Virtual Machine and SMT=4 that is 256 lines of output - even the biggest screen will not cope. We tried reducing the font in PuTTY to 6 point and still no luck. Amazingly, we learnt to read it this size font but it was easy to confuse "3" and "8" it is only one or two pixels different.

So what is the answer?

We have two answers!

First - Instead of using "c" to see the logical CPUs use "C" (Capital "c") and you get the graphs smaller and vertically. See below:

This shows 64 CPUs at a time and if you have more CPUs it will show another set below - this covers us up to 256 logical CPUs.

Second - What I call "Long Term stats" instead of dozens individual CPUs, we just monitor the machine level utilisation. This is started with "l" (lower case L). See below:

I added this mode when watching an Apache web server at a customer doing a benchmark a long time ago. It would change utilisation rapidly and this longer term view lets you visually see an average (see the "+" on the horizontal bar which is the current last update point. At 2 second updates and 72 data points = roughly two and a half minutes.

This view also gets the Auto-scaling Physical CPU view (hit "#") from May 2011 - see the other AIXpert blog about that feature.

Hope this helps, thanks, Nigel Griffiths.

Tags: powervm nmon term power aix cpu longer physical

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