Comments on: I Want My Memory, Apple!

By: Keith Lazuka

Keith Lazuka — Thu, 23 Jul 2009 00:49:22 +0000

Apple engineer “eskimo1″ wrote a detailed reply about the iPhone’s virtual memory system on the Apple Developer Forums: https://devforums.apple.com/message/49187#49187

By: A First Exposure to Memory Managment on the iphone

A First Exposure to Memory Managment on the iphone — Fri, 17 Jul 2009 03:53:56 +0000

[...] http://gamesfromwithin.com/?p=428 has a great blog post/discussion about memory concerns with regard to iphone development; much more [...]

By: Noel

Noel — Mon, 01 Jun 2009 00:40:56 +0000

Valentin, you should read my next post on memory and virtual memory systems

By: Valentin

Valentin — Sat, 30 May 2009 19:24:46 +0000

I’m not an OS programmer nor a dev. , but I’m just wondering why isn’t there an appication for the iPhone that can solve this issue like the Paging file in the Windows OS? On the smallest iPhones there are 8GB of HDD memory. With the OS on them there still are more than 6.5 GB of space. Why not create a program that allows ppl to allocate an amount of virtual memory to the OS? 64, 128 or 256 extra MB would solve all those problems users/devs are facing with.

Sorry if I’m talking nonsense for you guys, but as I said, I’m not a connaisseur .

By: Virtual Memory Paging Is The Lazy Man’s Caching Scheme

Virtual Memory Paging Is The Lazy Man’s Caching Scheme — Fri, 22 May 2009 18:11:36 +0000

[...] of the unintended side effects of my previous post on the horrible memory situation on the iPhone, was that some people pointed out it was possible to hook up a disk storage back end to the [...]

By: Where’d That Memory Go?

Where’d That Memory Go? — Fri, 15 May 2009 22:26:31 +0000

[...] My recent rant about the dismal situation of memory in the iPhone quickly became quite popular. Most people were either unaware of the situation, or completely agreed that it was a major stumbling block for any app that tries to make good use of the hardware. [...]

By: Tip: iPhone Virtual Memory at Under The Bridge

Tip: iPhone Virtual Memory at Under The Bridge — Fri, 15 May 2009 05:39:02 +0000

[...] us correct your misconception. It turns out that, indeed, there actually is. Take a look through this moderately amusing rant about the indeterminacy of memory allotments on the iPhone and into the comments. There’s a [...]

By: Owen

Owen — Thu, 14 May 2009 12:25:05 +0000

@Chuck – I actually experimented with that in Dapple during Alpha/Beta testing. The problem was that as soon as that popup comes up, the user immediately thinks that it’s something your app has done wrong, not the phone. I got a bunch of emails from testers after I put that in saying “I think *your app* broke…I got a warning telling me to reboot my phone” (emphasis mine). The problem being that they blame the app, not the OS. It’s a tricky problem to deal with; you want to provide the user with information, but not have them think it’s your fault.

By: Chuck Smith

Chuck Smith — Thu, 07 May 2009 21:58:05 +0000

I noticed that the Monopoly app gives a warning pretty much every time I run it that it recommends me to reboot my phone. I remember another wild west shooter that did the same. It’s a solution, but I admit not a very elegant one. I also really hope Apple fixes this in 3.0. I can also imagine that many 1-star app reviews have come from apps crashing on iPhones that were dangerously low on memory.

By: Hendrik

Hendrik — Thu, 07 May 2009 20:45:17 +0000

There actually is a virtual memory system pager. However you have to manually set it up.
Search for ‘mmap’ in Apple’s iPhone Developer Forum and you’ll find a very informative thread.
Basically, it works like this: In place of malloc, you create a file of the appropriate size and then memory map that file using mmap. The virtual memory pager will page in and out the memory pages as needed. This works both for read-only data (you can just use [NSData dataWithContentsOfMappedFile: ] for that) as well as read-write memory.

By: Stephen Darlington

Stephen Darlington — Thu, 07 May 2009 19:52:57 +0000

One other thing that affects the amount of memory you have available is when a user has jail broken their handset. If it’s also customised with weird versions of SpringBoard you can get up to 10Mb less than a stock iPhone — and the users complain when your app doesn’t work properly!

No convenient answers I’m afraid. I wrote about this a little more on my blog, but I definitely agree that one of the nice things about programming for the iPhone is that you’re not working with a moving target.

By: Villain

Villain — Thu, 07 May 2009 19:49:39 +0000

Our company is getting into iPhone development. At this point it's only been prep and research, but we will be hitting it full board soon. This information is good and will be something for which I now know to watch out. Great post. Thanks.

By: Noel

Noel — Thu, 07 May 2009 19:37:49 +0000

Graf, I wish I could just allocate all the memory up front. That’s the way I prefer to do it, but there are problems with that. You need to wait for other processes to free memory in order to get your memory, which could be a while (how long? No idea, need to time it). Also, background processes might need more memory all of a sudden (incoming phone call), so you might still be forced to free memory.

I definitely want to experiment with a lot of the suggestions so far. Some of these ways allow us to get around some of the memory problems, or at least make them more predictable. I still wish that Apple could just guarantee a minimum amount of memory though. It would make life a LOT easier!

By: Vezquex

Vezquex — Thu, 07 May 2009 19:26:01 +0000

How lame of Apple. There should be a special game mode that swaps everything to disk so that you can just use all the memory.

And Fisherman, you don’t have to apologize for your English. It’s easily above average.

By: Graf Algar

Graf Algar — Thu, 07 May 2009 19:12:22 +0000

Why not build your own heap class, and at the very start of your game, allocate the max you’ll ever need (say, 20mb or whatever). For the purposes of your game, only ever alloc/free from that custom heap.

A couple of benefits to this approach:

- You can, at startup, immediately see whether or not you have enough memory available for your game. If you don’t, either try scrubbing memory, or inform the user to reboot.
- Tighter control of allocations, memory leaks, and so on. Activity inside of that heap is specific to your game, and so you have the maximum amount of control possible.
- Less chance of running out of memory midgame by way of fragmentation from external parties, assuming you were able to alloc the initial 20mb chunk or whatever. Basically, if you were able to alloc your heap, you’re 99% guaranteed to run your game without a hitch (memory-wise).
- Makes porting the game to other platforms a little easier – since you’d just have to worry about where the initial mem alloc comes from. Everything else remains the same.