linux-kernel - Re: RSDL v0.31

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Message-ID: <20070317124458.GA32301@elte.hu>
Date:	Sat, 17 Mar 2007 13:44:58 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	jos poortvliet <jos@...nkamer.nl>
Cc:	Mike Galbraith <efault@....de>, Con Kolivas <kernel@...ivas.org>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: RSDL v0.31

* jos poortvliet <jos@...nkamer.nl> wrote:

> Op Saturday 17 March 2007, schreef Ingo Molnar:
> > so it is not at all clear to me that RSDL is indeed an improvement, 
> > if it does not have comparable auto-nice properties.
> 
> Wasn't the point of RSDL to get rid of the auto-nice, because it 
> caused starvation, unpredictable behaviour and other problems?

it doesnt really get rid of it, it replaces it with another mechanism 
that is fundamentally unfair too.

RSDL has _another_, albeit more hidden "auto-nice" behavior: this time 
expressed not via the plain manipulation of priorities based on the 
sleep average, but expressed via the quota-depletion flux of tasks over 
time, fed into a complex dance of rotating priorities - which 
quota-depletion flux is in essence a sleep average too, just more 
derived and more hardcoded.

or looking at it from another angle, code size:

   text    data     bss     dec     hex filename
  15750      24    6008   21782    5516 sched.o.vanilla
  15960     360    6336   22656    5880 sched.o.rsdl

there's no reduction in complexity, it just moved elsewhere.

	Ingo
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