Re: dosemu with different speed

[Ryan Underwood <nemesis-lists@icequake.net>]

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On Sat, Apr 24, 2004 at 09:32:39PM +0100, Andrew Brooks wrote:
> Ryan Underwood wrote:
> > What do you mean by "speed"?  You want different scheduling
> > priorities
> > for each one?  Can just use 'nice'.  
>
> I have a DOS application which must respond to an interrupt within a
> certain amount of time.  I have tried using nice to raise the priority
> but it still misses occasionally.

Yep. DOSEMU is not DOS.  If you have realtime constraints, we must look
into calling sched_setscheduler() on user's behalf to set policy to
SCHED_RR or SCHED_FIFO.  But that will require root permission.  It
is also possible for your machine to be completely locked-up if the DOS
task fails in any way.

> Do you think it's safe to run dosemu in the realtime scheduling class?
> (in which case I would leave hogthreshold at 1 = nicest)

I think DOSEMU itself is mostly safe.  The problem is the DOS program
you are running.  If it ever goes into an uncontrollable loop (i.e.
polling with interrupts disabled), you are screwed and will have to
reboot when running SCHED_FIFO.  SCHED_RR should not be so bad because
the scheduler is guaranteed to seize control periodically, but only
other SCHED_RR processes are guaranteed to get any CPU time.  So you
would have to have a SCHED_RR bash running too in order to be able to
gain control of the other process.

-- 
Ryan Underwood, <nemesis@icequake.net>

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