linux-kernel - Re: [PATCH 3/7] idle, thermal, acpi: Remove home grown idle implementations

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Date:	Wed, 20 Nov 2013 20:38:03 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Arjan van de Ven <arjan@...ux.intel.com>
cc:	Peter Zijlstra <peterz@...radead.org>, lenb@...nel.org,
	rjw@...ysocki.net, Eliezer Tamir <eliezer.tamir@...ux.intel.com>,
	Chris Leech <christopher.leech@...el.com>,
	David Miller <davem@...emloft.net>, rui.zhang@...el.com,
	jacob.jun.pan@...ux.intel.com,
	Mike Galbraith <bitbucket@...ine.de>,
	Ingo Molnar <mingo@...nel.org>, hpa@...or.com,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 3/7] idle, thermal, acpi: Remove home grown idle
 implementations

On Wed, 20 Nov 2013, Arjan van de Ven wrote:
> 
> but for powerclamp to work, it needs to inject a deep idle....  I'm
> very ok using generic abstractions for that, but the abstraction
> needs to then include a "don't be nice about picking shallow C
> states for performance reasons, just pick something very deep"
> parameter.

And that's what you should have done in the first place. Make the
generic code take a parameter to indicate that. Or tell the scheduler
to throttle the machine and go deep idle. That would also be helpful
to others who might need some similar thing.

No, you went with the worst design:

    - Hack it into some random driver
    - Export random core interfaces so it's harder to change them
    - Let others deal with the fallout

I'm cleaning up that kind of mess for more than 9 years now and I'm
really disappointed that you went over to the "who cares, works for
me" camp.

I can lively remember our discussions when we were cleaning up the
whole timer mess together in order to make NOHZ actually useful. Your
cursing about such code was definitely impressive back then.

Thanks,

	tglx

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