Re: Calculating real cpu usage of Xen domains correctly! (PATCH)

[Rob Gardner <rob.gardner@hp.com>]

Ian Pratt wrote:
>>OK, here is a patch which provides fine grained cpu utilization 
>>reporting. Some notes:
> 
> 
> I really can't see the point of this patch -- it isn't necessary to log
> every scheduling operation to record CPU usage for a domain over
> multiple time scales. 

Yes, obviously you are correct. I am sorry for not explaining this patch 
better. Let me start from the beginning. We developed this code to 
collect various kinds of data. One of the things it does is measure cpu 
usage. However, that is not all it does, since as you rightly say, such 
complicated code is not necessary to to just measure cpu usage. When 
several people started talking about measuring cpu usage, I just 
volunteered this code to solve the problem. So I do not propose this 
code solely to measure cpu usage.

For instance, one thing the code can do is to measure how much time 
elapses while a domain is runnable, versus how much cpu time it actually 
receives. This metric might be one simple way of expressing 'quality of 
service.' In order to do this, some scheduler activity needs to be 
monitored. Hence the more heavy handed approach. We have other ideas in 
mind that require very fine grained measurements, some have been 
implemented, some not. I hope to share some of the other metrics soon.

Additionally, this is somewhat experimental code in that it was written 
this way in order to facilitate future measurements that we may not have 
  considered yet. Can we let some people try it out and see if it 
provides this framework?

Thanks,
Rob


-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click