Re: [QUESTION] 2.4.x nice level

[george anzinger <george@mvista.com>]

Rik van Riel wrote:
> 
> On Mon, 9 Apr 2001, george anzinger wrote:
> > SodaPop wrote:
> > >
> > > I too have noticed that nicing processes does not work nearly as
> > > effectively as I'd like it to.  I run on an underpowered machine,
> > > and have had to stop running things such as seti because it steals too
> > > much cpu time, even when maximally niced.
> 
> > In kernel/sched.c for HZ < 200 an adjustment of nice to tick is set up
> > to be nice>>2 (i.e. nice /4).  This gives the ratio of nice to time
> > slice.  Adjustments are made to make the MOST nice yield 1 jiffy, so
>         [snip 2.4 nice scale is too limited]
> 
> I'll try to come up with a recalculation change that will make
> this thing behave better, while still retaining the short time
> slices for multiple normal-priority tasks and the cache footprint
> schedule() and friends currently have...
> 
> [I've got some vague ideas ... give me a few hours to put them
> into code ;)]

You might check out this:

http://rtsched.sourceforge.net/

I did some work on leveling out the recalculation overhead.  I think, as
the code shows, that it can be done without dropping the run queue lock.

I wonder if the wave nature of the recalculation cycle is a problem.  By
this I mean after a recalculation tasks run for relatively long times
(50 ms today) but as the recalculation time approaches, the time reduces
to 10 ms.  Gets one to thinking about a way to come up with a more
uniform, over time, mix.

George

George