linux-kernel - Re: Renice X for cpu schedulers

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Message-ID: <20070420053412.GA628@gnuppy.monkey.org>
Date:	Thu, 19 Apr 2007 22:34:12 -0700
From:	Bill Huey (hui) <billh@...ppy.monkey.org>
To:	"Michael K. Edwards" <medwards.linux@...il.com>
Cc:	Con Kolivas <kernel@...ivas.org>, ray-gmail@...rabbit.org,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Matt Mackall <mpm@...enic.com>,
	William Lee Irwin III <wli@...omorphy.com>,
	Peter Williams <pwil3058@...pond.net.au>,
	Mike Galbraith <efault@....de>, ck list <ck@....kolivas.org>,
	linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Bill Huey (hui)" <billh@...ppy.monkey.org>
Subject: Re: Renice X for cpu schedulers

On Thu, Apr 19, 2007 at 05:20:53PM -0700, Michael K. Edwards wrote:
> Embedded systems are already in 2007, and the mainline Linux scheduler
> frankly sucks on them, because it thinks it's back in the 1960's with
> a fixed supply and captive demand, pissing away "CPU bandwidth" as
> waste heat.  Not to say it's an easy problem; even academics with a
> dozen publications in this area don't seem to be able to model energy
> usage to the nearest big O, let alone design a stable economic
> dispatch engine.  But it helps to acknowledge what the problem is:
> even in a 1960's raised-floor screaming-air-conditioners
> screw-the-power-bill machine room, you can't actually run a
> half-decent CPU flat out any more without burning it to a crisp.
> stupid.  What's your excuse?  ;-)

It's now possible to QoS significant parts of the kernel since we now
have a deadline mechanism in place. In the original 2.4 kernel, TimeSys's
irq-thread allowed for the processing of skbuffs in a thread under a CPU
reservation run category which was use to provide QoS I believe. This
basic mechanish can now be generalized to many place in the kernel and
put it under scheduler control.

It's just a matter of who and when somebody is going take on this task.

bill

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