On Monday 12 March 2007 05:11, Al Boldi wrote:
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> Al Boldi wrote:
> > BTW, another way to show these hickups would be through some kind of a
> > cpu/proc timing-tracer.  Do we have something like that?
>
> Here is something like a tracer.
>
> Original idea by Chris Friesen, thanks, from this post:
> http://marc.theaimsgroup.com/?l=linux-kernel&m=117331003029329&w=4
>
> Try attached chew.c like this:
> Boot into /bin/sh.
> Run chew in one console.
> Run nice chew in another console.
> Watch timings.
>
> Console 1: ./chew

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> Console 2: nice -10 ./chew

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> pid 669, prio  10, out for    5 ms
> pid 669, prio  10, out for   65 ms

One full expiration

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> pid 669, prio  10, out for    6 ms
> pid 669, prio  10, out for   65 ms

again

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> Console 2: nice -15 ./chew
> pid 673, prio  15, out for    6 ms
> pid 673, prio  15, out for   95 ms

again and so on..

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> OTOH, mainline is completely smooth, albeit huge drop-outs.

Heh. That's not much good either is it.

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> Thanks!

And thank you! I think I know what's going on now. I think each rotation is 
followed by another rotation before the higher priority task is getting a 
look in in schedule() to even get quota and add it to the runqueue quota. 
I'll try a simple change to see if that helps. Patch coming up shortly.

-- 
-ck
-
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