Re: More thread scheduling observations
Re: More thread scheduling observations
- Subject: Re: More thread scheduling observations
- From: Ian Ollmann <email@hidden>
- Date: Mon, 6 May 2002 18:48:31 -0700
>
After hearing the arguments from Bill and Ian, I have decided to
>
implement a user "prefs" scheme which will allow the user to setup a
>
feeder priority according to their requirements. I am designing it so
>
it will range from "cooperative" to "greedy".
Hmm, that doesn't quite seem like the right thing to do to me. Let me make
a categorical statement here -- I agree 100% with Bill, and to the extent
that we may appear to differ, he is correct.
I never intended to advocate or even appear to advocate using "low
priority" fixed-priority threads in preference to real time threads for
real time needs. If you have a real time need, use a real time thread.
That is where you get your guarantee. I was just pointing out that fixed
priority threads are preferable to standard timeshare threads for (more)
steady data delivery because they do not dip towards 0 priority in the way
that timeshare threads do. The real time thread has a fixed priority, by
the way. It also has an exceptionally high priority to make sure that you
do get the time you need when you need it.
The whole thing about choosing the lowest safe priority level was for
threads that obviously can afford to be preempted by some things --
threads that do not need a real time guarantee, but which do perform best
if they get CPU access fairly frequently. For these, a lower priority
fixed priority thread is probably appropriate, especially if they take up
a lot of CPU, or do other things that might make executing at a 96
priority problematic. Now, whether you believe that it is vital or just
merely important that your feeder thread always gets time is up to you to
decide.
Ian
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Ian Ollmann, Ph.D. email@hidden
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