How much real memory should my iphone app be using? What's going too high?
A:
I think available memory may depend on several factors such as device model, how long it has not been rebooted etc.
You should not rely on some fixed values but instead try to use as little memory as possible and implement -(void)applicationDidReceiveMemoryWarning:(UIApplication *)application in your application delegate and/or -didReceiveMemoryWarning in your view controllers to handle low memory warnings there and free unused memory.
Vladimir
2010-02-04 08:13:47
+1
A:
Keeping an eye on -(void)applicationDidReceiveMemoryWarning:(UIApplication *)application is definitely important, but if this is game, chances are the assets (notably textures presently on screen) can't simply be deallocated when that warning is received.
If you're a bit on the high side (20 MB +) I would recommend doing a bit of testing. Using Instruments and the Object Allocation tool (Run > Run with Performance Tool > Object Allocations) you can monitor how large your memory footprint gets. Then, try running Safari and fill the pages, then a few games and whatever else you can to get the memory higher, and see how your app performs.
In my testing for a recent release, 24 MB seemed to be pretty safe, and is a number I've heard elsewhere. Once you get above 30 or so MB, chances are your users will start having rare crashes (which happens to be the case for us, verified by crash reports). The higher you go, the more crashes users will see. There's no specific limit though, for the sake of testing I've pushed my app on an iPhone 3G up to 70 MB before, it just isn't likely to work for most, nor for long.
Requesting on the iTunes page that users restart their devices can help, though there's no guarantees it'll be effective.
Also, this is all assuming devices prior to the 3GS / 3rd Gen iPod Touch. If the app merely runs on an older device, it should have no problem on the newer ones (which have twice as much ram, 256 MB).
Jazon
2010-02-04 09:48:57