[cadynce] Model CPU Utlizations Predict End-to-End Times

[Patrick Lardieri]

Hi Alan,

Interesting thoughts that I am not sure I understand fully.

At the 100,000 ft level it seems you are offering an alternative to 
scheduling theory to predict the response time.  Specifically, you seem 
to be suggesting that a linear regression model could be used to predict 
the mean end-to-end response time of an appstring by considering the  
CPU utilizations  of the critical path components  as the independent 
variables.  Is this correct?
 
A couple of questions:

1) It is not clear in the slide what the independent variables really 
are. Are the the software components specified worst case execution 
time? The software component's measured mean execution time? The 
utilization on the CPU that the application runs on?

2) The equation on slide 2 has one coefficient but slide 3 implies there 
is a coefficient per CPU term. Which is correct?

3) You are estimating mean e2e times. Correct? Typically we are also 
interested in worst case end to end times. Do you intend to consider 
that problem as well?

Thanks,

Patrick



Alan F. Karr wrote:
> Colleagues,
>
> Here is some interesting evidence that the pieces of our tool chain 
> are actually links.
>
> We took all configurations tested to date with 42, 43 or 44 processors 
> (As discussed yesterday, this is in some sense "where the action is") 
> and asked whether the /*model-derived*/ CPU utilizations along the 
> critical path predict the /*measured*/ end-to-end times, also along 
> the critical path. So far, the only models are considered are linear 
> regressions. The fits are quite remarkably good.
>
> A PowerPoint file summarizing the results is attached. Comments and 
> reactions are welcome. I will attempt to put this on the wiki.
>
> --- Alan
>
> -- 
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