linux-kernel - Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]

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Date:	Thu, 19 Apr 2007 09:55:04 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Mike Galbraith <efault@....de>
cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [Announce] [patch] Modular Scheduler Core and Completely Fair
 Scheduler [CFS]

On Thu, 19 Apr 2007, Mike Galbraith wrote:

> On Thu, 2007-04-19 at 09:09 +0200, Ingo Molnar wrote:
> > * Mike Galbraith <efault@....de> wrote:
> > 
> > > With a heavily reniced X (perfectly fine), that should indeed solve my 
> > > daily usage pattern nicely (always need godmode for shells, but not 
> > > for mozilla and ilk. 50/50 split automatic without renice of entire 
> > > gui)
> > 
> > how about the first-approximation solution i suggested in the previous 
> > mail: to add a per UID default nice level? (With this default defaulting 
> > to '-10' for all root-owned processes, and defaulting to '0' for 
> > everything else.) That would solve most of the current CFS regressions 
> > at hand.
> 
> That would make my kernel builds etc interfere with my other self's
> surfing and whatnot.  With it by EUID, when I'm surfing or whatnot, the
> X portion of my Joe-User activity pushes the compile portion of root
> down in bandwidth utilization automagically, which is exactly the right
> thing, because the root me in not as important as the Joe-User me using
> the GUI at that time.  If the idea of X disturbing root upsets some,
> they can move X to another UID.  Generally, it seems perfect for here.

Now guys, I did not follow the whole lengthy and feisty thread, but IIRC 
Con's scheduler has been attacked because, among other argouments, was 
requiring X to be reniced. This happened like a month ago IINM.
I did not have time to look at Con's scheduler, and I only had a brief 
look at Ingo's one (looks very promising IMO, but so was the initial O(1) 
post before all the corner-cases fixes went in).
But this is not a about technical merit, this is about applying the same 
rules of judgement to others as well to ourselves.
We went from a "renicing X to -10 is bad because the scheduler should 
be able to correctly handle the problem w/out additional external plugs" 
to a totally opposite "let's renice -10 X, the whole SCHED_NORMAL kthreads 
class, on top of all the tasks owned by root" [1].
>From a spectator POV like myself in this case, this looks rather "unfair".



[1] I think, before and now, that that's more a duck tape patch than a 
    real solution. OTOH if the "solution" is gonna be another maze of 
    macros and heuristics filled with pretty bad corner cases, I may 
    prefer the former.


- Davide


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