Re: [SCHED] wrong priority calc - SIMPLE test case

At 02:52 PM 12/30/2005 +0100, Paolo Ornati wrote: 
WAS: [SCHED] Totally WRONG prority calculation with specific test-case
(since 2.6.10-bk12)
http://lkml.org/lkml/2005/12/27/114/index.html

On Wed, 28 Dec 2005 10:26:58 +1100
Con Kolivas <kernel@xxxxxxxxxxx> wrote:

> The issue is that the scheduler interactivity estimator is a state machine and
> can be fooled to some degree, and a cpu intensive task that just happens to
> sleep a little bit gets significantly better priority than one that is fully
> cpu bound all the time. Reverting that change is not a solution because it
> can still be fooled by the same process sleeping lots for a few seconds or so
> at startup and then changing to the cpu mostly-sleeping slightly behaviour.
> This "fluctuating" behaviour is in my opinion worse which is why I removed
> it.

Trying to find a "as simple as possible" test case for this problem
(that I consider a BUG in priority calculation) I've come up with this
very simple program:

------ sched_fooler.c -------------------------------

Ingo seems to have done something in 2.6.15-rc7-rt1 which defeats your little proggy. Taking a quick peek at the rt scheduler changes, nothing poked me in the eye, but by golly, I can't get this kernel to act up, whereas 2.6.14-virgin does.

-Mike (off to stare harder rt patch) 

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