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

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Message-ID: <20070415233909.GE2986@holomorphy.com>
Date:	Sun, 15 Apr 2007 16:39:09 -0700
From:	William Lee Irwin III <wli@...omorphy.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Matt Mackall <mpm@...enic.com>, Con Kolivas <kernel@...ivas.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]

On Sun, Apr 15, 2007 at 10:48:24PM +0200, Ingo Molnar wrote:
> 2) plugsched did not allow on the fly selection of schedulers, nor did
>    it allow a per CPU selection of schedulers. IO schedulers you can 
>    change per disk, on the fly, making them much more useful in
>    practice. Also, IO schedulers (while definitely not being slow!) are 
>    alot less performance sensitive than CPU schedulers.

One of the reasons I never posted my own code is that it never met its
own design goals, which absolutely included switching on the fly. I
think Peter Williams may have done something about that. It was my hope
to be able to do insmod sched_foo.ko until it became clear that the
effort it was intended to assist wasn't going to get even the limited
hardware access required, at which point I largely stopped working on
it.

On Sun, Apr 15, 2007 at 10:48:24PM +0200, Ingo Molnar wrote:
> 3) I/O schedulers are pretty damn clean code, and plugsched, at least
>    the last version i saw of it, didnt come even close.

I'm not sure what happened there. It wasn't a big enough patch to take
hits in this area due to getting overwhelmed by the programming burden
like some other efforts of mine. Maybe things started getting ugly once
on-the-fly switching entered the picture. My guess is that Peter Williams
will have to chime in here, since things have diverged enough from my
one-time contribution 4 years ago.

-- wli
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