On Tue, Aug 10, 2010 at 06:28:39PM -0700, david@xxxxxxx wrote: > On Tue, 10 Aug 2010, Paul E. McKenney wrote: > > >On Tue, Aug 10, 2010 at 09:38:49AM +0100, Alan Cox wrote: > >>>situation you call out can occur with manual suspend-to-RAM already: > >>>the fact is that this is a design choice. You could indeed make a > >> > >>Losing data is a design choice ? The application set a timer, the OS > >>shouldn't be ignoring it in that situation. It might want to delay it, it > >>might want to warn the user its hogging things it shouldnt (powertop, > >>battery usage monitors in Android etc) > > > >Hmmm... Let's put the two approaches side by side so that we can compare > >them more easily: > > > > Opportunistic Suspend Idle + Timer Jitter > > > > Set timer Set timer > > Suspend OS delays timer > > Resume OS continues delaying timer > > Timer fires Timer fires > > > >These two cases look quite similar to me. > > > >But as you say, the battery can run out. So let's add that to the > >comparison: > > > > Opportunistic Suspend Idle + Timer Jitter > > > > Set timer Set timer > > Suspend OS delays timer > > Battery runs out Battery runs out > > Data loss Data loss > > > >The two cases still look quite similar. You might note, quite correctly, > >that the time between suspend and resume might be quite a bit longer than > >the typical time that the OS delays a timer. But the power consumption > >on some platforms is quite a bit lower in the suspend case than it is > >in the delayed-timer case. > > it has been stated that the android can hit the exact same power > state either with sleep or suspend, and that the same clock can wake > it up (it appears as a timer expiring for sleep, or an alarm for > suspend, but it's the same clock firing the signal) > > so in at least some cases the hardware supports doing both with > equal efficiency. It indeed has been so stated. But in this section we were discussing data loss, not hardware power-state capabilities. > >>>But that doesn't guarantee that solutions developed for PCs and laptops > >>>will be optimal (or even usable) on cellphones. Sufficient difference > >> > >>Your cellphone is to all intents a laptop from ten years ago, it even has > >>a similar display resolution and internet availability. The underlying > >>difference between the two is solely form factor - the laptop had a > >>better keyboard. > > > >There are similarities and differences. You have called out some of > >the similarities. Differences include the more-aggressive hardware > >power management on cellphones, the greater number and variety of > >hardware accelerators on cellphones, battery capacity, and, as you say, > >physical size. People currently use cellphones differently than they > >do laptops or desktops. The usage might converge, but we will see. > >There is as much reason to expect increasing specialization as there > >is to expect increasing convergence. > > You are talking about Android as if it was a cell phone only thing, > it's not. there are shipping tablets (and I believe netbooks, i.e. > laptops) running andoid. I was talking about cellphones. But yes, Android (and thus suspend blockers) are used for tablets as well as cellphones, thank you for reminding me! > >>>As to busting all apps, lthough there have been situations where busting > >>>all the apps turned out to be the right thing to do, I agree that these > >>>situations are extremely rare. Such situations are usually associated > >>>with the emergence of a new high-volume platform. > >> > >>Like Microsoft Windows 16bit co-operative multi-tasking ? It's rarely > >>right. It's merely that in certain cases the value in the market is large > >>enough that it can be used as a big stick to beat people into doing lots > >>of usually wasted work. > > > >Interesting choice of example. I do well remember the Sequent hardware > >guys' frustration when the old printer driver would monopolize the desktop > >while printing their large documents. The fact was that Microsoft's > >co-operative multi-tasking required all applications to be well behaved, > >just as does your approach to power efficiency. > > and wakelocks require all applications that can take a wakelock be > well behaved. and applications that do nt take a wakelock directly > cannot expect to run unless something else takes a wakelock on their > behalf Almost. Suspend blockers require that only those portions of a PM-driving application that hold a suspend blocker be carefully written to avoid wasting power. Thanx, Paul _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
