Message-ID: <40E0F1D6.5090506@yahoo.com.au>
Date: Tue, 29 Jun 2004 14:36:38 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: Felipe Alfaro Solana <felipe_alfaro@linuxmail.org>
CC: Con Kolivas <kernel@kolivas.org>,
       linux kernel mailing list <linux-kernel@vger.kernel.org>,
       Willy Tarreau <willy@w.ods.org>
Subject: Re: [PATCH] Staircase scheduler v7.4
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Felipe Alfaro Solana wrote:
> On Mon, 2004-06-28 at 22:11 +1000, Con Kolivas wrote:
> 
> 
>>The design of staircase would make renicing normal interactive things
>>- -ve values bad for the latency of other nice 0 tasks s is not
>>recommended for X or games etc. Initial scheduling latency is very
>>dependent on nice value in staircase. If you set a cpu hog to nice -5 it
>>will hurt audio at nice 0 and so on. Nicing latency unimportant things
>>with +ve values is more useful with this design. If you run X and
>>evolution at the same nice value they will get equal cpu share for
>>example so moving windows means redrawing evolution and X moving get
>>equal cpu. Nicing evolution +ve will make X smoother compared to
>>evolution redrawing and so on...
> 
> 
> OK, just a few thoughts...
> 
> 1. Both -mm3 and -np2 suffer from delays when redrawing "damaged"
> windows (windows which were covered and now are being exposed): while
> moving heavily a window over the screen, "damaged" windows are not
> redrawn. I would say this is a sign of starvation. However, this does
> not happen with -ck3 that is able to redraw "damaged' windows even while
> heavily moving a window all over the screen.
> 
> I can see this by looking at some icons that are lying on my desktop.
> With -mm3 and -np2, they are hardly redrawn while heavily moving a
> window all around. With -ck3, I can see the icons and their respective
> labels all the time.
> 
> 2. Both -mm3 and -np2 show a very smooth behavior when moving windows
> all around the screen. However, -ck3 is somewhat a little bit jerky. I
> think this is a consequence of point number 1.
> 

Try having X at a lower priority (higher nice) and it shouldn't get
as much of the CPU. I think this is really a fundamental tradeoff
that you can't do much about.

> 3. Both -mm3 and -ck3 are inmune to CPU hogs when mantaining
> interactivity: running "while true; do a=2; done" doesn't seem to affect
> the interactive behavior of them. I check this by running this CPU hog
> and hovering my mouse over KXDocker, which is a nice applet for KDE
> similar to the Mac OS X docker. KXDocker is another CPU hog by itself,
> but plays nicely with the "while true" loop. However, -np2 seems to
> suffer a little bit from starvation, as KXDocker animations don't feel
> smooth.
> 

Hmm, in that case bash should go straight down to lowest priority,
so it shouldn't impact too much on others' CPU usage... I'll see
what I can do though, timeslices could still be a little too big.
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