I don't know how to do this for Linux based VMs (which is what I'll need in the end) but can do some experiments with Apple Xcode Instruments.

That's something I've wanted to do for a long time as this gives deep insight on how a program is behaving.

http://en.wikipedia.org/wiki/Instruments_%28application%29
http://developer.apple.com/library/mac/#documentation/DeveloperTools/Conceptual/InstrumentsUserGuide/Introduction/Introduction.html

Thanks for looking into this.

Maybe could we do a chapter on these matters in one of the Pharo books.

The point of having idle VMs is that when one machine is hit by a peak of usage, the other instances can swallow the load. Now, I am not talking about a single EC2 VM, but a group of them, each having a set of VMs.

FWIW, AIMP3 playing MP3s all the time is 9%-11% on an old PIV 3Ghz, while Skype takes 1% idling

Phil

On Fri, May 31, 2013 at 11:26 AM, Norbert Hartl <norbert@hartl.name> wrote:

Am 27.05.2013 um 10:17 schrieb phil@highoctane.be:

I was looking at the output of "top" for while and Pharo was trusting the top spot indeed.

Well, I'll look at all that this evening and give back the impressions.

I want to run several instances of Pharo on the box and it will for sure add up. Say, 20 x 2% gives an awful lot.

What is the use of having 20 idle images on one server? :) �I think you can't easily say that it always adds on top. If your image is running at 100% the 2% off even if fully countable wouldn't be that much. But nevertheless it is a valid point and I cannot see pharo becomes more modern by stop polling in the mid-term future.

Anyway I played a little bit with the tweaks and there are things that make me wonder. I raised the limit for server mode but didn't get much benefit. Having a cycle pause of 100ms in serverMode and stopping the ui process still gave me a 1% CPU usage which is really a lot. Does anyone know in-depth what an image is doing? How to investigate? Maybe there are a lot of native polling things involved, too?�

I need to dig deeper.

Norbert

Phil

On Mon, May 27, 2013 at 10:07 AM, Norbert Hartl <norbert@hartl.name> wrote:

Am 27.05.2013 um 09:49 schrieb Sven Van Caekenberghe <sven@stfx.eu>:

BTW, load & cpu usage numbers can be very hard to interpret.�

really? CPU usage is pretty easy and you can see this in most OSses directly. 100% CPU usage is full :) Load isn't that much harder. It's just the load of the scheduler queue. So if some needs a rule of thumb

safe CPU load = number of cores/processes * 0.7
theoretical optimal CPU load = number of core/processes

Everything above should really be investigated because you entered the zone where �additional CPU load can drive your machine unresponsive.�

You have less CPU usage but high load? Investigate I/O usage!�

I know you know that, Sven. I just wanted to mention it because this comes up from time to time. Compared to memory consumption, CPU, scheduler and I/O are easier targets IMHO.

For Phil the point isn't the health of the system. It is EC2. You have to pay for the CPU usage on EC2 so I think he had the impression there is room for improvement. And indeed there is. But if you calculate it through it isn't really a factor.

Norbert