Re: [RFC] Scheduler work, part 1: High-level goals and interface.

[Jeremy Fitzhardinge <jeremy@goop.org>]

Dan Magenheimer wrote:
> And that's the oversimplification I think.  Just
> because Intel provides a rule-of-thumb that the extra
> thread increases performance by 30% doesn't mean that
> it is a good number to choose for scheduling purposes.
>   

Actually the 70% was a number I plucked out of the air with no 
justification at all.

> I suspect (and maybe this has even already been proven)
> that this varies from 0%-100% depending on the workload,
> and may even vary from *negative* to *more* than 100%.
> (Yes, I understand that i7 is supposed to be better than
> the last round of HT... but is it always better?)
>   

The only way to know is by measurement, ideally with some specific 
performance counter which tells you what went on in that last 
timeslice.  But if this is a big issue, you can always disable HT, as 
lots of people did the last time around.

    J