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Apple Executive Confirms: Manually Quitting Apps Doesn't Improve Battery Life (bgr.com)
An anonymous reader writes: Apple software engineering VP Craig Federighi recently dispelled one of the more long-standing myths about iPhone battery life. In short, if you spend a few minutes every day double clicking the iPhone home button and manually closing up applications in an effort to maintain battery life, you're wasting your time. The reality is that the applications you see upon opening up the multitasking pane are actually nothing more than static images intended to represent a list of your most recently used applications. Apple support documents have indicated, "generally, there's no need to force an app to close unless it's unresponsive." Apple support docs further explain: "After you switch to a different app, some apps run for a short period of time before they're set to a suspended state. Apps that are in a suspended state aren't actively in use, open, or taking up system resources."
Except Waze... Waze is a battery hog. I always quit that as soon as I'm done with its navigation features.
This is for regular apps. Apps that have background mode enabled can run in background and can consume CPU cycles. They can even use GPS, WiFi, LTE etc. That consumes battery. Most of the running or GPS apps run just fine in background. Otherwise they'd just stop recording once the screen locks or, worse, keep the screen on at all times.
Which the OS will automatically free up as necessary by killing off suspended processes. Why waste your own time doing it when it offers no real benefit and the OS will free up the memory as soon as it needs it anyhow?
Well, the thing is free memory is wasted memory.
Unless you *need* more free memory (in which case the system will GC / free on its own), there's no cost to leaving used pages in memory. Think of it like cache.
The next time you launch an app you just cleared, it has to reload it all from MMC, recreate the activity, execute the startup routines, etc.
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This was by far the most common myth about smartphone battery life I heard. The next one is to turn off GPS after use to save battery (as if it changed anything when not using an application using the GPS)
That depends on the OS. We've moved on from the days when memory taken off and put back on the heap is fragmented and can't be assigned until it's the largest remaining chunk again.
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Everyone is listing off apps that do suck cpu cycles. So apple is wrong about this. So is google. We keep getting these explanation from these vendors which doesnt seem to match real world experiences. Thats because vendors use imaginary scenarios, static apps that dont use resources like gps, cpu or network in the background, which is fine for a game, but reporting apps use cycles.
Google goes even farther and says task killers DECREASE battery life, because the task killer will run often. Total bullshit, but as its easy to test and see the results.
I think think the vendors are using unrealistic use cases, apple and google thinks the average use will just call/text and brows the web, so all other apps are a "rare" thing so its excluded.
Which the OS will automatically free up as necessary by killing off suspended processes. Why waste your own time doing it when it offers no real benefit and the OS will free up the memory as soon as it needs it anyhow?
Problem is some apps are persistent. It's like removing Skype from your tasktray if you're going into an airplane - no need for that app to constantly poll.
Plus Waze essentially tracks you all the time (not just when you're asking it to navigate) - best to keep that shit off unless you're using it.
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Apps which are put to the background are allowed to run for a little while to let them finish up what they were doing (e.g. saving something). Then they're suspended - their state is written to disk and they're flushed from memory. The screenshot is saved so you can see it in the list, and if you reopen it the app will be restarted from the saved state.
Apps can register themselves as requiring to run full time in the background, examples are navigators, messaging apps, etc. These will not be suspended, and can eat the battery. If you add one of those flags to your app without actually having justification to do so, you'll be rejected from the app store.
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Depends on how smart your memory controller is. Unused RAM doesn't need to be strobed. If everything in use lives on one chip, why bother sending electrons to the other chips until you need them?
Stallman gets a lot of shit but, more often than not, he's right. People laugh him off because he presents very stark predictions of a dystopian future that is in sharp contrast to what one sees at any given moment. I think he understands The Slow Boil that we are currently experiencing while the majority of society just sees a shiny toy and covets it.
No, they're not. On iOS, no application is allowed to stay permanently resident in RAM and immune from jetsam.
If they've been set as "allowed" to update in the background, they essentially can.
On my iPhone 6 Plus, within the last 6-12 months I've had multiple occasions where I'd be sitting at home in the evening, and a pop-up window would open saying something along the lines of "Waze is still accessing your location information - do you want to let that continue?"
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Horsesh*t. Or rather, Stalman Foot-cheese.
Stalman was talking about software. You' can change your system image on your phone. You can even make one yourself if you want to. You can make your own apps that work the way you want. And for those who aren't so fanatical, they're free to stick with stock system images that come with that all-important support (even if it's less than 2 years in most cases - it's not like it stops working after support ends).
If everyone did it Stalman's way, small cheap and smart smartphones wouldn't exist. "Everything should be open" - well, no manufacturer is going to put the big bucks into r & d making a product that anyone else can just legally knock off. Thus there would be no economies of scale, and too many hardware and software incompatibilities.
Them's the facts. Or do you want to go back to the time of home-brew computers, and a slew of different architectures and operating systems with software only available on any one particular system in a hit or miss fashion? It was fun, but it was also a bit of a PITA.
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Push all apps you don't actually need to the cloud (delete).
"Storing your apps in the cloud" and deleting the local copy is stupid. It takes time and energy to upload them, and more to download them each time you want to use them.
"Transparent" is a shit show that trades on every stereotype going. A man in drag is NOT a transsexual.
On an iPad2 with newest iOS, several resource hungry apps will NOT be able to run unless you manually go in and remove all apps from the list.
That's with several gb free, so it seems very likely that some RAM must be used.
The reason task killers can decrease battery life on Android is that when an app subscribed to an event and isn't running, it is started. So the task killer may cause the app to be regularly restarted instead of just staying in memory.
Task killers only help with buggy apps that can sometimes go crazy instead of properly getting into standby.
Some task killers are a bit better and can prevent apps from restarting. These can really improve your battery life, in exchange, you usually lose all background features from the app (notifications, sync, ...)