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

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Date:	Sun, 15 Apr 2007 17:39:33 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Willy Tarreau <w@....eu>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	hui Bill Huey <billh@...ppy.monkey.org>,
	Con Kolivas <kernel@...ivas.org>, ck list <ck@....kolivas.org>,
	Peter Williams <pwil3058@...pond.net.au>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>, Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]


* Willy Tarreau <w@....eu> wrote:

> Ingo could have publicly spoken with them about his ideas of killing 
> the O(1) scheduler and replacing it with an rbtree-based one, [...]

yes, that's precisely what i did, via a patchset :)

[ I can even tell you when it all started: i was thinking about Mike's
  throttling patches while watching Manchester United beat the crap out
  of AS Roma (7 to 1 end result), Thuesday evening. I started coding it
  Wednesday morning and sent the patch Friday evening. I very much
  believe in low-latency when it comes to development too ;) ]

(if this had been done via a comittee then today we'd probably still be 
trying to find a suitable timeslot for the initial conference call where 
we'd discuss the election of a chair who would be tasked with writing up 
an initial document of feature requests, on which we'd take a vote, 
possibly this year already, because the matter is really urgent you know 
;-)

> [...] and using part of Bill's work to speed up development.

ok, let me make this absolutely clear: i didnt use any bit of plugsched 
- in fact the most difficult bits of the modularization was for areas of 
sched.c that plugsched never even touched AFAIK. (the load-balancer for 
example.)

Plugsched simply does something else: i modularized scheduling policies 
in essence that have to cooperate with each other, while plugsched 
modularized complete schedulers which are compile-time or boot-time 
selected, with no runtime cooperation between them. (one has to be 
selected at a time)

(and i have no trouble at all with crediting Will's work either: a few 
years ago i used Will's PID rework concepts for an NPTL related speedup 
and Will is very much credited for it in today's kernel/pid.c and he 
continued to contribute to it later on.)

(the tree walking bits of sched_fair.c were in fact derived from 
kernel/hrtimer.c, the rbtree code written by Thomas and me :-)

	Ingo
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