linux-kernel - Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

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Date:	Thu, 27 May 2010 15:26:44 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
cc:	Florian Mickler <florian@...kler.org>,
	Vitaly Wool <vitalywool@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>, felipe.balbi@...ia.com,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linux PM <linux-pm@...ts.linux-foundation.org>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

On Wed, 26 May 2010, Alan Cox wrote:

> > The power efficiency of a mobile device is depending on a sane overall
> > software stack and not on the ability to mitigate crappy software in
> > some obscure way which is prone to malfunction and disappoint users.
> 
> Even if you believe the kernel should be containing junk the model that
> works and is used for everything else is resource management. Not giving
> various tasks the ability to override rules, otherwise you end up needing
> suspend blocker blockers next week.

We definitely will need them when we want to optimize the kernel
resource management on a QoS based scheme, which is the only sensible
way to go IMNSHO.

> A model based on the idea that a task can set its desired wakeup
> behaviour *subject to hard limits* (ie soft/hard process wakeup) works
> both for the sane system where its elegantly managing hard RT, and for
> the crud where you sandbox it to stop it making a nasty mess.

Right, the base system can set sensible defaults for "verified" apps,
which will work most of the time except for those which have special
requirements and need a skilled coder anyway. And for the sandbox crud
the sensible default can be "very long time" and allow the kernel to
ignore them at will.

> Do we even need a syscall or will adding RLIMIT_WAKEUP or similar do the
> trick ?

That might be a good starting point.

Thanks,

	tglx
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