Re: [2.4.17/18pre] VM and swap - it's really unusable

yodaiken
2002-01-14T13:52:01Z

I forgot the line that says: "Oliver pointed out the immediate problem but .."

On Mon, Jan 14, 2002 at 06:45:48AM -0700, yodaiken@fsmlabs.com wrote:
> On Mon, Jan 14, 2002 at 02:17:46PM +0200, Momchil Velikov wrote:
> > >>>>> "yodaiken" == yodaiken <yodaiken@fsmlabs.com> writes:
> > yodaiken> It's not even clear how preempt is supposed to interact with SCHED_FIFO.
> >
> > How so ? The POSIX specification is not clear enough or it is not to be followed ?
>
> POSIX makes no specification of how scheduling classes interact - unless something changed
> in the new version.
>
> But more than that, the problem of preemption is much more complex when you have
> task that do not share the "goodness fade" with everything else. That is, given a
> set of SCHED_OTHER processes at time T0, it is reasonable to design the scheduler so
> that there is some D so that by time T0+D each process has become the highest priority
> and has received cpu up to either a complete time slice or a I/O block. Linux kind of
> has this property now, and I believe that making this more robust and easier to analyze
> is going to be an enormously important issue. However, once you add SCHED_FIFO in the
> current scheme, this becomes more complex. And with preempt, you cannot even offer the
> assurance that once a process gets the cpu it will make _any_ advance at all.
>
>
>
> --
> ---------------------------------------------------------
> Victor Yodaiken
> Finite State Machine Labs: The RTLinux Company.
> www.fsmlabs.com www.rtlinux.com

--
---------------------------------------------------------
Victor Yodaiken
Finite State Machine Labs: The RTLinux Company.
www.fsmlabs.com www.rtlinux.com