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

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Date:	Thu, 27 May 2010 19:13:11 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arve Hjønnevåg <arve@...roid.com>,
	Florian Mickler <florian@...kler.org>,
	Vitaly Wool <vitalywool@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Paul@...p1.linux-foundation.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 Thu, 2010-05-27 at 18:07 +0100, Matthew Garrett wrote:
> On Thu, May 27, 2010 at 07:04:38PM +0200, Thomas Gleixner wrote:
> > On Thu, 27 May 2010, Matthew Garrett wrote:
> > > Sure, if you're not using opportunistic suspend then I don't think 
> > > there's any real need for the userspace side of this. The question is 
> > > how to implement something with the useful properties of opportunistic 
> > > suspend without without implementing something pretty much equivalent to 
> > > the userspace suspend blockers. I've sent another mail expressing why I 
> > > don't think your proposed QoS style behaviour provides that.
> > 
> > Opportunistic suspend is just a deep idle state, nothing else.
> 
> No. The useful property of opportunistic suspend is that nothing gets 
> scheduled. That's fundamentally different to a deep idle state.

I think Alan and Thomas but certainly I am saying is that you can get to
the same state without suspend.

Either you suspend (forcefully don't schedule stuff), or you end up
blocking all tasks on QoS/resource limits and end up with an idle system
that goes into a deep idle state (aka suspend).

So why isn't blocking every task on a QoS/resource good enough for you?
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