Re: [PATCH] sched: rsdl improvements

[Artur Skawina <art_k@o2.pl>]

Con Kolivas wrote:
> Note no interactive boost idea here.
> 
> Patch is for 2.6.21-rc4-mm1. I have not spent the time trying to bring other
> bases in sync.

I've tried RSDLv.31+this on 2.6.20.3 as i'm not tracking -mm.

> Further improve the deterministic nature of the RSDL cpu scheduler and make
> the rr_interval tunable.
> 
> By only giving out priority slots to tasks at the current runqueue's
> prio_level or below we can make the cpu allocation not altered by accounting
> issues across major_rotation periods. This makes the cpu allocation and
> latencies more deterministic, and decreases maximum latencies substantially.
> This change removes the possibility that tasks can get bursts of cpu activity
> which can favour towards interactive tasks but also favour towards cpu bound
> tasks which happen to wait on other activity (such as I/O) and is a net
> gain.

I'm not sure this is going in the right direction... I'm writing
this while compiling a kernel w/ "nice -20 make -j2" and X is almost
unusable -- even the x pointer jumps instead of moving smoothly like
it always did; I had to stop the build to be able to quickly finish
this as the latency is making it hard to properly position the cursor...
Hmm, this is weird; I've tried various nice values for the build and
19 is the only one triggering this, w/ 18 and less the cursor moves
smoothly, but there are short sub-second stalls. nice=0 isn't much
different.
RSDL 0.31 was behaving properly, and only exhibited problems when
the box was overloaded w/ non-niced tasks; Right now even a properly
niced background job kills interactivity completely.

artur