How much memory an application can use ?

Did you read this in Appendix A of the iOS App Programming Guide? Also, the Performance Tuning section describes your responsibility to use memory efficiently and provides some ideas on how to use lazy loading to reduce memory footprint.

To manage program memory, iOS uses essentially the same virtual memory system found in Mac OS X. In iOS, each program still has its own virtual address space, but unlike Mac OS X, the amount of usable virtual memory is constrained by the amount of physical memory available. This is because iOS does not support paging to disk when memory gets full. Instead, the virtual memory system simply releases read-only memory pages, such as code pages, when it needs more space. Such pages can always be loaded back into memory later if they are needed again.

The OS manages memory - asking how much your app can use is a windows-centric idea, I think...

As of iOS 5 there is only 1 level of memory warning – free up memory or be killed. If you are getting the warning, you are on the chopping block, period :).

See Cocoa Memory Management [ https://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/MemoryMg mt/MemoryMgmt.html]

Use Instruments to test if you must.

And remember, unused memory is wasted memory 🙂

Ken

The OS manages memory - asking how much your app can use is a windows-centric idea, I think...

Windows manages memory just like OS X. And probaby every other operating system with a virtual memory manager and protected addressing.

http://msdn.microsoft.com/en-us/library/windows/desktop/aa366525

I thought we were talking about iOS...

Mobile is same story. Even the old Windows Mobile used the same memory management approach. I remember long ago when Microsoft removed the ability for users to explicity terminate apps from the UI because there was no need, it only slowed things down when the user later switched back to that app. And there was a low memory notification for apps to reduce memory footprint, just like iOS.

How to you 'set' the memory for an OS app?

The concept of application memory 'requirements' is non-existent on iOS... It's simply not the same. Unlike desktop apps that come with a minimum spec, etc.

Totally common in Windows/Mac....show me one iOS app in the store that comes with anything like that spec. There are none, because it isn't the same environment at all.

On iOS, an app will get what it needs dynamically....and be killed if it gets greedy in the process. Windows/OS X won't blindly kill an app...they just restrict it's performance. If an app misbehaves in terms of memory it leads to a crash. On iOS, it leads to shot to the head.

I have never 'set' the memory on a Windows app. Is there a way to do that?

iOS does an excellent job managing memory, but I have not seen a fundamental difference in the way iOS manages memory to other operating systems that include memory management services.

For me, the difference begins with the fact that unlike OS X, iOS has no garbage collection. The two seem to be converging, w/OS X moving towards iOS, however, so how that plays out going forward remains to be seen.

For now, they don't work the same...I suppose that's a good thing at this point in time 🙂

Ken

True.

I wonder when required adherence to the application life-cycle management model (app states and transition events) that are part of iOS, Android, and WP will migrate to the deskop operating systems. That really pushes the developer to play nice with resources.