On Sun, Aug 01, 2010 at 03:49:04PM -0700, Arjan van de Ven wrote: > On Sun, 1 Aug 2010 12:27:08 -0700 > "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > > > 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. > > this is why operating systems for mobile devices offer heartbeat > services... where apps subscribe to and do background work like > checking email at "convenient" times. > > I'm not sure if the OS you use on your desktop has one, but MeeGo and > Maemo and I'm pretty sure Android and most other mobile Linux OSes have > one. It's a higher level activity alignment layer, well above the > kernel. Thank you, good to know! Thanx, Paul _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
