Linux-kernel mailing list archive 1999-23,: Re: I: [OT] R: R: How does Linux work?

# Re: I: [OT] R: R: How does Linux work?

Bert Thomas (bert@brothom.nl)
Wed, 09 Jun 1999 10:02:11 +0100

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In <19990608213447.C7067@pcep-jamie.cern.ch>, on 06/08/99
at 09:34 PM, Jamie Lokier <lkd@tantalophile.demon.co.uk> said:

>Marco Ermini wrote:
>> > This is false. I'm not an NT fan, but its rt scheduling algorithms
>> > are similar to Linux. There is a range of priorities that use an
>> > adaptive scheduling algorithm for time-sharing, like linux, and
>>
>> Try it yourself: open the task manager and
>> change the priority of a multimedia player
>> to real-time on a Pentium 200. Then wait
>> until the player it's over (mouse locked too).

>Do you mean everything stops *even if the RT task blocks*?

>Otherwise Linux has the same problem. If you set a task to have RT
>priority, ordinary tasks stop running until the RT task blocks or
>terminates.

>I don't know if NT's multimedia player blocks or not, but I'd guess not.
>A typical video game would never block so of course would lock out
>ordinary tasks if it had RT priority.

>RT priority is not to be used lightly. Games shouldn't use it except for
>special things: maybe for the sound mixer thread. Then those threads
>should take great care not to hog the CPU.

If memory serves me well, I believe that NT doesn't do priority inversions
so that a high-priority thread can be blocked by a lower-priority thread
and therefore miss a deadline.

-----------------------------------------------------------
Bert Thomas <bert@brothom.nl>
-----------------------------------------------------------

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