linux-kernel - Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.

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Message-ID: <20100507175025.GA23952@srcf.ucam.org>
Date:	Fri, 7 May 2010 18:50:25 +0100
From:	Matthew Garrett <mjg@...hat.com>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Brian Swetland <swetland@...gle.com>,
	Alan Stern <stern@...land.harvard.edu>,
	mark gross <mgross@...ux.intel.com>, markgross@...gnar.org,
	Len Brown <len.brown@...el.com>, linux-doc@...r.kernel.org,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.

On Fri, May 07, 2010 at 10:35:49AM -0700, Tony Lindgren wrote:
> * Matthew Garrett <mjg@...hat.com> [100507 10:08]:
> > The situation is this. You've frozen most of your userspace because you 
> > don't trust the applications. One of those applications has an open 
> > network socket, and policy indicates that receiving a network packet 
> > should generate a wakeup, allow the userspace application to handle the 
> > packet and then return to sleep. What mechanism do you use to do that?
> 
> I think the ideal way of doing this would be to have the system running
> and hitting some deeper idle states using cpuidle. Then fix the apps
> so timers don't wake up the system too often. Then everything would
> just run in a normal way.

Effective power management in the face of real-world applications is a 
reasonable usecase.

> For the misbehaving stopped apps, maybe they could be woken
> to deal with the incoming network data with sysfs_notify?

How would that work? Have the kernel send a sysfs_notify on every netwrk 
packet and have a monitor app listen for it and unfreeze the rest of 
userspace if it's frozen? That sounds expensive.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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