Real-time Scheduling

Real-time Scheduling

Post by Tan Teik Gu » Wed, 21 Jun 1995 04:00:00



I need to implement a real-time scheduler as part of my project.

any pointers to ftp sites, books, papers will be very much appreciated.

Tan Teik Guan

 
 
 

Real-time Scheduling

Post by Chet D. Hay » Thu, 22 Jun 1995 04:00:00



Quote:> I need to implement a real-time scheduler as part of my project.

> any pointers to ftp sites, books, papers will be very much appreciated.

> Tan Teik Guan

The University of Colorado (Denver, Colorado) has done some research with/for Hughes Aircraft in connection to Space based systems.  I know that some of items Hughes has had to deal with is real time scheduling, and I do believe that UCD might have some more information avalibale on the work they have done.  I do believe that they have discussed simulated anneling, other forms of neural nets., surgical algorithims, and a few others.  Sorry, I can't give you a site or refer you to a book, but hopefully this
might point you in the right direction.

 
 
 

1. Mixed Time-Share & real-Time scheduling

 I seem to have this problem:

 Process Proc is started in real time, it in turns creates  THR_BOUND thrA.

 And then it drops itself in time share queue and creates THR_BOUND thrB.
(Actually there are a multitude of time-share and real-time threads.)

 Now thrA runs for a while (some milliseconds, say 15 ) and then it sleeps
for some milliseconds. (This is actually done by some interrupt mechanism
but that probably is not important either) and then thrB comes in prints some
data generated by thrA and goes to sleep. So far so good. Now however
if I go to another window and do an "ls" or another command, what I am
seeing is that if "ls" starts when the time-share thread thrB is running,
it can preempt thrB, and when the time to run thrA comes again, scheduler
doesn't necessarily run thrA. Soit appears that some piece of code
in the scheduler, when it gets a level 10 interrupt, it checks the
process table, and not the LWP table to find out if any real-time
LWPs are waiting or not. So if there is NO processes in real-time
queue, it assumes that there are no real-time LWPs waiting, and skips
that portion of the scheduler.... This is pure conjecture, but I am at
a loss to explain this behaviour. This can make me sometimes lose 10 or
20 milliseconds, invalidating houirs worth of run sometimes.
It works correctly if the process is in the real-time queue. Any
suggestions. (we got and tried patch -54 just to be sure...)

Sinan

PS: platform is SS10/512MP

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