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

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Date:	Wed, 2 Jun 2010 11:07:07 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Arve Hjønnevåg <arve@...roid.com>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Florian Mickler <florian@...kler.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Peter Zijlstra <peterz@...radead.org>,
	Paul@...p1.linux-foundation.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>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

On Wed, 2 Jun 2010, Arve Hjønnevåg wrote:
> 2010/6/2 Thomas Gleixner <tglx@...utronix.de>:
> > On Tue, 1 Jun 2010, Arve Hjønnevåg wrote:
> >>
> >> Because suspend itself causes you to not be idle you cannot abort
> >> suspend just because you are not idle anymore.
> >
> > You still are addicted to the current suspend mechanism. :)
> >
> 
> No I want you to stop confusing low power idle modes with suspend. I
> know how to enter low power modes from idle if that low power mode is
> not too disruptive.

What prevents us from going into a disruptive mode from idle ? I don't
see a reason - except crappy ACPI stuff, which I'm happy to ignore.

> > If I understood you correctly then you can shutdown the CPU in idle
> > completelty already, but that's not enough due to:
> >
> >    1) crappy applications keeping the cpu away from idle
> >    2) timers firing
> >
> > Would solving those two issues be sufficient for you or am I missing
> > something ?
> 
> Solving those two is enough for current android phones, but it may not
> be enough for other android devices.

In which way ? May not be enough is a pretty vague statement.

> 1 is not solvable (meaning we cannot fix all apps),

We can mitigate it with cgroups and confine crap there, i.e. force
idle them.

> and 2 is difficult to fix since the periodic
> work is useful while the device is actually in use. One possible way
> to solve 2 is to allow timers on a not-idle clock.

That's what I had in mind.

> Unrelated to Android, I also want to use opportunistic suspend on my
> desktop.

I expect that intel/amd fixing their stuff is going to happen way
before we sprinkled suspend blockers over a full featured desktop
distro.

Thanks,

	tglx