Re: Guaranteeing processing speed...

Rogier Wolff (R.E.Wolff@BitWizard.nl)
Wed, 13 Oct 1999 15:26:06 +0200 (MEST)

David Woodhouse wrote:
>
> R.E.Wolff@BitWizard.nl said:
> > Well, having an application request how much bogomips are available,
> > and then tell the OS how much bogomips it will need is also less than
> > ideal. The MPEG player will need to know the number of mpeg-mips and
> > not bogo-mips.
>
> The OS would have to deal in time, not *mips of any kind. It's up to the app
> to calibrate the speed required for whatever it happens to be doing, and take
> into account any variation which it might experience.

So, setting the program to a high RT priority, and then calibrating is
going to give the same results as when the OS tells the app that it
can take 50% of the CPU.

Note that this won't work "fine". If there is nothing "realtime"
running, and I ask the OS: what percentage of the CPU do you have
available? I'm going to get the answer: "100%". If I then use (close
to) 100%, the X server for instance will be starved. Kind of useless
mpeg player then. So the developer decides that if the OS says 100%,
he will request 90%. Fine. Now someone else has a system where the X
server requires significantly more CPU horsepower to display the same
stream. Now what?

Conclusion: The "ask the OS for a guaranteed percentage of the CPU"
sysstem isn't all that easy to use anyway....

Roger.

-- 
** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 **
*-- BitWizard writes Linux device drivers for any device you may have! --*
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