linux-kernel - RE: [RFD] Automatic suspend

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Date:	Tue, 17 Feb 2009 18:18:59 -0600
From:	"Woodruff, Richard" <r-woodruff2@...com>
To:	Arjan van de Ven <arjan@...radead.org>
CC:	Brian Swetland <swetland@...gle.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Kyle Moffett <kyle@...fetthome.net>,
	Oliver Neukum <oliver@...kum.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	Pavel Machek <pavel@....cz>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	mark gross <mgross@...ux.intel.com>,
	Uli Luckas <u.luckas@...d.de>,
	Igor Stoppa <igor.stoppa@...ia.com>,
	Len Brown <lenb@...nel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>
Subject: RE: [RFD] Automatic suspend

> On Tue, 17 Feb 2009 09:32:46 -0600
> "Woodruff, Richard" <r-woodruff2@...com> wrote:
>
> > > so use range timers / timer slack for those apps that you do not
> > > trust. That is not a big deal, and solves the issue of timer
> > > wakeups...
> >
> > I not so sure it is that straight forward in practice.  End systems
> > integrate a lot of 3rd party software who view performance 1st and
> > have no thought of power.
>
> you know that with the range timers/slack, you can control the
> "rounding" of the timer of the application, right?

I've not explored user space for this.

Can on a per-application basis some controlling application cause timers of a target process to be rounded or is it global? Or do you need to link the new application to use special glib variants (as described in OLS papers a few years ago)?

> You can *directly* throttle the number of wakeups an application causes
> that way to a value you set.

Are you talking about your work as seen in lwn.net summary?

http://lwn.net/Articles/296578/

Your change here does look like something which could be used to control timers.  Don't you still need some dynamic way to set the fuzz/slack if its globally applied?  It seems like you might want some timers precise and others fuzzy.

Would the holding of a wakelock or some activity counter be a good trigger for switching rounding time?  If wakelocks held "minor adjustment" else "major adjustment"

Thanks for the good pointer assuming I understood it in quick scan.

Thanks,
Richard W.

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