Video: Windows Phone multitasking explained.

A 21 minute video about multitasking on Windows Phone appeared yesterday on WMPU.

You might want to take a look at Andre’s post about multitasking on Windows Phone.

Nokia phone have been doing multitasking since possibly forever (well in phone world anyway). One of Symbian’s many assets was true multitasking. Apps all live running in the background. This sometimes caused problems when you left too many things in the background. Over time apps got bigger, but Symbian phones got stuck with less and less percentage of free RAM. N900 with Maemo 5 had more RAM + virtual RAM and with the new live grid screens let users switch between applications quickly and effortlessly. However, like Symbian^3, the more things that were left running, the quicker the battery died. Another issue even on both is that when the limits were pushed (at it happens earlier on S^3) that the phone severely slows down (worse if you have apps at start up that then run in the background).

The folks from Microsoft say they weren’t ready with letting developers let apps run in the background, taking up resources and killing the battery. (I’m not sure how much multitasking affects the MeeGo way).

This is why Windows Phone did not have 3rd party multitasking (though core apps are able to run, e.g. music player)

• In WP7, when an app goes into the background, the process is terminated. Switching back creates a new process and it is brought to the foreground.
• In Mango, instead of the process being terminated, the threads instead are frozen so it cannot use CPU/Battery/Bandwidth, but the memory is marked reclaimable.  If  you run another app that needs the memory that app was using, the process can instantly be killed.
• If there’s enough memory in the phone (there is a minimum requirement for Windows Phone, but manufacturers can bring more) processes won’t be killed. But if you have too many apps, instead of the whole phone dying and crashing when opening a new app, frozen apps are then closed to free up more RAM.
• 5 are kept in the backstack, and if you need more memory, the last one used will be terminated. The reasoning behind this is that the majority of PC users apparently switch between a few apps, mostly the most recent and not the ones they used a while ago (having been forced to use chrome without firefox’s multirows, I found this the case at least when browsing). The thing I have most issue with is the linear multitasking interface (WebOS, Symbian^3, QNX) – I want grid please.
• Apps running in the foreground aren’t in the same multitasking environment as say the tiles which bring live updated information. The latter runs only for about 25 seconds per half hour, with only 6MB in use. Note – lots of things in Maemo 5 and Symbian^3 homescreen tended to kill the battery more. When low on power, these agents stop to save battery. Agents, as Andre explained, run on behalf of the app but use less resources
• There’s other things mentioned in the video that I’ve skipped (the bit about round robin management for resource intensive tasks – 14minutes in).
• You can select if an agent will run in the background or not (sort of like switching widgets to offline, except with individual management). This would be useful if say  you wanted to turn off location tracking for a particular app.
• For the most of it, this method of multitasking is designed for users to switch between applications very quickly without having to think too much or at all about task management and so not adversely affect battery life.

Video: WMPU.

Category: Windows Phone