linux-kernel - Re: [ANNOUNCE] RSDL completely fair starvation free interactive cpu scheduler

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Date:	Tue, 13 Mar 2007 05:05:04 +1100
From:	Con Kolivas <kernel@...ivas.org>
To:	Al Boldi <a1426z@...ab.com>
Cc:	ck list <ck@....kolivas.org>, linux-kernel@...r.kernel.org
Subject: Re: [ANNOUNCE] RSDL completely fair starvation free interactive cpu scheduler

On Tuesday 13 March 2007 01:14, Al Boldi wrote:
> Con Kolivas wrote:
> > > > The higher priority one always get 6-7ms whereas the lower priority
> > > > one runs 6-7ms and then one larger perfectly bound expiration amount.
> > > > Basically exactly as I'd expect. The higher priority task gets
> > > > precisely RR_INTERVAL maximum latency whereas the lower priority task
> > > > gets RR_INTERVAL min and full expiration (according to the virtual
> > > > deadline) as a maximum. That's exactly how I intend it to work. Yes I
> > > > realise that the max latency ends up being longer intermittently on
> > > > the niced task but that's -in my opinion- perfectly fine as a
> > > > compromise to ensure the nice 0 one always gets low latency.
> > >
> > > I think, it should be possible to spread this max expiration latency
> > > across the rotation, should it not?
> >
> > There is a way that I toyed with of creating maps of slots to use for
> > each different priority, but it broke the O(1) nature of the virtual
> > deadline management. Minimising algorithmic complexity seemed more
> > important to maintain than getting slightly better latency spreads for
> > niced tasks. It also appeared to be less cache friendly in design. I
> > could certainly try and implement it but how much importance are we to
> > place on latency of niced tasks? Are you aware of any usage scenario
> > where latency sensitive tasks are ever significantly niced in the real
> > world?
>
> It only takes one negatively nice'd proc to affect X adversely.

I have an idea. Give me some time to code up my idea. Lack of sleep is making 
me very unpleasant.

-- 
-ck
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