Date: Sun, 1 Aug 2010 12:27:08 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Mikael Abrahamsson <swmike@swm.pp.se>
Cc: Arjan van de Ven <arjan@infradead.org>,
        linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        arve@android.com, mjg59@srcf.ucam.org, pavel@ucw.cz,
        florian@mickler.org, rjw@sisk.pl, stern@rowland.harvard.edu,
        swetland@google.com, peterz@infradead.org, tglx@linutronix.de,
        alan@lxorguk.ukuu.org.uk
Subject: Re: Attempted summary of suspend-blockers LKML thread
Message-ID: <20100801192708.GM2470@linux.vnet.ibm.com>
Reply-To: paulmck@linux.vnet.ibm.com
References: <20100731175841.GA9367@linux.vnet.ibm.com>
 <20100731215214.2543c07e@infradead.org>
 <20100801054816.GI2470@linux.vnet.ibm.com>
 <alpine.DEB.1.10.1008010812450.24755@uplift.swm.pp.se>
 <alpine.DEB.1.10.1008010838430.24755@uplift.swm.pp.se>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.1.10.1008010838430.24755@uplift.swm.pp.se>
User-Agent: Mutt/1.5.20 (2009-06-14)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2924
Lines: 58

On Sun, Aug 01, 2010 at 08:49:43AM +0200, Mikael Abrahamsson wrote:
> On Sun, 1 Aug 2010, Mikael Abrahamsson wrote:
> 
> >it's just that mobile (low power) wasn't the intended target of
> >the application when it was written, and this commonly shows.

Good points in both this and your earlier post!!!

> I have another aspect I just thought about. I work for a telephony
> company. We provide Internet connectivity throught various means,
> DSL, Ethernet to the Home, mobile etc.
> 
> For ETTH and DSL, network usage is pretty straight forward, you send
> packets, they get delivered pretty quickly with low marginal cost
> per packet. For mobile, this is not quite so simple. Mobile networks
> are designed for terminal/UE (user equipment) to use low power, so
> they go down in low power state after a while. Let's take the case
> of 3G/HSPA:
> 
> After a short while (second) of idleness (no packets being sent),
> the mobile network negotiates away the high speed resources (the one
> that enables multimegabit/s transfers) and tries to give it to
> someone else. After approximately 30 seconds, the terminal goes to
> "idle", meaning it has no network resources at all. Next time it
> wants to send something (or the network wants to deliver something
> to it), network resources need to be negotiated again. This can take
> 1-2 seconds and uses battery power of course. It also consumes
> resources in the operator network (because mobility control units
> need to talk to base stations, tunnels need to be re-negotiated
> etc).
> 
> Anyhow, my point is that not only is there a benefit in having
> multiple applications wake up at the same time for power reasons
> within the device, there is also a point in having coordination of
> their network access. If a device is running 3 IM programs at the
> same time, it'd be beneficial if they were coordinated in their
> communication with their Internet servers. Same goes for the "check
> for new email" application. If they all were optimized to only wake
> up the network connectivity once every 180 seconds instead of doing
> it when the individual application felt like it, power and other
> resources would be saved by all involved parties.

This is a good point.  Within some limits, the timer-aggregation
changes that have gone into Linux can handle this, but I am not sure
whether or not 180 seconds is within the reasonable boundaries for
timer jitter.

Of course, the timers might be synchronized upon wakeup after a
sufficiently long suspension, but they would not necessarily stay
synchronized without the help of some other mechanism, such as the
afore-mentioned timer-aggregation changes.

						Thanx, Paul
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/