Kinds of models (was: Lock elision test results)

[David Collier-Brown]

| On Fri, 2013-07-05 at 18:27 -0700, Andi Kleen wrote:
> Torvald Riegel <triegel@redhat.com> writes:
>
>> We need to model performance in some way
>> to be able to find robust tuning parameters,
> No, no, the right way is to run lots of work loads (that is real
> applications) and see what parameters work best.

| Andi, we're not in disagreement here.  I definitely agree that we need
| to have lots of input data.  But any tuning algorithm that we build is
| conceptually based on some model of performance.


I think you're using two different senses of "model".
Perhaps it woul be better to distinguish "mental model", which is ons's
understanding of what happens, from "mathematical model", which is a
restatement of the program in question in a different form, that of
mathematics.

--dave

-- 
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
davecb@spamcop.net           |                      -- Mark Twain
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