iOS Multitasking

This is something I’ve wondered about since iOS 4.How does iOS handle the recently running apps bar in terms of memory, CPU and background tasks. I caught this post by Fraiser Speirs a couple of days ago: Misconceptions About iOS Multitasking.

John Gruber over at Daring Fireball sums it up like this:

The system suspends apps running in the background automatically. The system removes suspended apps from memory automatically, when needed. Manually zapping all apps from this list is a voodoo placebo. The whole point of iOS’s multitasking model is that you, the user, should not have to worry about managing which applications are running and which are not. If you were supposed to do that, apps would have a Quit command. They don’t. You just go home, and the system should take care of the rest.

via Daring Fireball: You Do Not Need to Manually Manage iOS Multitasking.

I’ve cleared my apps from the recently running bar more than a few times. When you double click the Home button on an iPhone, iPad or iPod Touch running iOS 4 or later, the interface slides up to reveal a bar of recently run apps. If you touch and hold on an icon in this tray, the icons will start to quiver and a red X will appear, allowing you to “quit” the app. I used to nuke any app that continues to use the GPS when I’m done with it and with early versions of the Skype app. Sounds like those were unnecessary steps.

Here is Apple’s support page about multitasking. It has the official party line and links to other useful tips.

I’m learning every day!

January 4, 2012 Link

  • shauna ehninger

    The more you know! Gracias for taking the time to research and post about this as I have often wondered these things myself.

  • A

    Interesting.  That said, when I want to do a hard reset on an app that isn’t responding properly and I don’t want to turn off my entire device, the multitasking plain works wonders.

  • Doug Springer

    Hmm. Although that makes sense (since it’s how it should be), it always seems to me that my battery drains faster when there are several forgotten (usually photo) apps still “running” in the tray, so I make a habit of killing anything I’m not using.

    • Doug Springer

      As an update, I took my fully-charged iPhone 4 out of its dock this morning at 7, and all I’ve done with it was send/receive about half a dozen texts. As of 2 PM, I’m down to 65% battery, so I checked and there were 6 apps in the tray other than Messages that I had forgotten to close. Since I can’t see a handful of txts using a third of my battery, I blame the open apps.

    • blurb

      So after you nuke all the apps in your tray does your battery life settle down?

      • Doug Springer

        Yep. If I make sure to leave ‘nothing running’, my battery meter will barely move. Half a dozen open apps, and it drops quickly. Close them, back to barely moving. I’ve done the experiment intentionally and accidentally a few times (usually after iOS upgrades). It’s easier for me to gauge because I don’t use the phone a lot – mainly screen-hungry apps or music – so voice calling doesn’t enter into it.

  • Lisa Folb

    I just recently learned about quitting the jiggly apps via multitasking bar, and was placebo’d into thinking the draining battery issue would be solved. Sorry to hear that this is not a real fix :-(
    Any thoughts, research, indicators on what one could do to improve battery life when it starts to decline rapidly?
    (leaning towards a full reset/rebuild)

    • blurb

      Turn off iCloud by logging out? I did a test where I logged out of my iCloud account and my data usage and battery life were markedly improved. I believe the phone is trying to do something no over WiFi. There are a lot of theories out there, but this simple step helped me.

  • Bumbling

    I’m with you on the GPS apps though – if you don’t manually kill them, the location pointer remains in the top right even when you’re out of the app, which surely suggests it’s still running, and therefore draining battery?

  • Bobbie

    This was so helpful. I couldn’t figure out why Words with Friends was updating on my iPhone and not on my iPad – and just discovered almost every single app was running in the background! Got rid of them all, restarted, and WWF is all fixed. Thanks!

  • christel hull

    working for AT&T we see a lot of people who complain about their battery lives.  we have found in most cases that closing out those apps each night, had helped extend the life of the battery.  be this a placebo or not, the “common man” will be the first to let us know if we are just blowing smoke or not.  and the concensus is that it works.  be that as it may, i still suggest clearing out the task bar out each night just to be on the safe side. 

  • Charles

    A note on GPS apps. There are two types of backgrounding for GPS apps. Active GPS which is what you normally see when you are using an app is only active in the background for navigation apps and such that really need a very accurate location.

    Any other app, Foursquare, Omnifocus, etc uses a passive method that determines your location based on the cell phone towers to send you alerts. That pretty much goes on all the time anyway so it uses no extra power. There isn’t much of a reason to kill GPS apps either.

  • minxlj

    I use this constantly to just make it easier to navigate between apps (if I’ve got 30 running it takes just as much time to find it as it does to look in the home screen and go into a folder to go back into an app, but if I’ve only got the key 3 or 4 there I can double click the button and access them MUCH quicker). I just like a tidy workspace, so I remove ones I’m not currently using.

    I also use this to quit apps that are hanging or misbehaving. Sadly Facebook’s app and a few others are so buggy that this is necessary.

    For battery life: I switch wifi off unless I’m connecting to a specific one, and switch Location Services off entirely via Settings if battery is really running low and I’m not near a charger.

    • blurb

      Interesting about switching wifi off. I’ve held the opinion that wifi was less of a battery hit than using 3G. If you keep wifi on and turn off “Ask to Join Networks” I’ve found that helps battery life significantly if I’m out and about.

      I think there are misbehaving apps, to be sure. And nuking it in the recent apps tray is one way to deal with them. I have to think this is why Apple included the option to delete apps in the recent apps tray.

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