Re: [PATCH] O13int for interactivity

[Con Kolivas <kernel@kolivas.org>]

On Tue, 5 Aug 2003 12:11, Nick Piggin wrote:
> Con Kolivas wrote:
> >Changes:
> >
> >Reverted the child penalty to 95 as new changes help this from hurting
> >
> >Changed the logic behind loss of interactive credits to those that burn
> > off all their sleep_avg
> >
> >Now all tasks get proportionately more sleep as their relative bonus drops
> >off. This has the effect of detecting a change from a cpu burner to an
> >interactive task more rapidly as in O10.
> >
> >The _major_ change in this patch is that tasks on uninterruptible sleep do
> > not earn any sleep avg during that sleep; it is not voluntary sleep so
> > they should not get it. This has the effect of stopping cpu hogs from
> > gaining dynamic priority during periods of heavy I/O. Very good for the
> > jerks you may see in X or audio skips when you start a whole swag of disk
> > intensive cpu hogs (eg make -j large number). I've simply dropped all
> > their sleep_avg, but weighting it may be more appropriate. This has the
> > side effect that pure disk tasks (eg cp) have relatively low priority
> > which is why weighting may be better. We shall see.
>
> I don't think this is a good idea. Uninterruptible does not mean its
> not a voluntary sleep. Its more to do with how a syscall is implemented.
> I don't think it should be treated any differently to any other type of
> sleep.
>
> Any task which calls schedule in kernel context is sleeping volintarily
> - if implicity due to having called a blocking syscall.
>
> >Please test this one extensively. It should _not_ affect I/O throughput
> > per se, but I'd like to see some of the I/O benchmarks on this. I do not
> > want to have detrimental effects elsewhere.
>
> Well the reason it can affect IO thoughput is for example when there is
> an IO bound process and a CPU hog on the same processor: the longer the
> IO process has to wait (after being woken) before being run, the more
> chance the disk will fall idle for a longer period. And of course the
> CPU uncontended case is somewhat uninteresting when it comes to a CPU
> scheduler.

I've already posted a better solution in O13.1

Con