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POiOS 5 + iPad 1 = Less Memory Available
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  1. POiOS 5 + iPad 1 = Less Memory Available
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    copied!<p>I have a problem with an existing application for iPad. It is quite sophisticated application written partly native (downloading, local caching and so on), partly using Sencha Touch for UI (without PhoneGap).</p> <p>Application runs fine on both iPad 1 and iPad 2 under iOS4. But with public release of iOS 5 aproblem appears for iPad 1 users. Application crashes after several seconds of work. Some guys <a href="https://discussions.apple.com/thread/3400742?start=15&amp;tstart=0" rel="nofollow">write</a> that instead of 78 there are only 30 megs of memory available for iPad 1 under iOS 5. And the other blackbox is the UIWebView. Nobody knows its internal limitations.</p> <p>I have a few ideas how to optimize JavaScript and HTML aspect. For example I've optimized structure and reduce memory allocations in scripts as I could. I've also replaced IMG tags with DIV + background-image. But crashes remains.</p> <p>Below is the insane solution to the problem.</p> <p><strong>Solution</strong></p> <p>There are memory warnings but I can release neither something native nor anything inside JavaScript, I thought. So I decided to do ridiculous thing - to allocate the dummy array of several megabytes and release it on memory warning. This is nuts but it works for me: I could allocate up to 100 megs of RAM on start with simple malloc()</p> <pre><code>// Member variable void* dummy; // - (void)init dummy = malloc(100000000L); </code></pre> <p>and free it with free() when system asks.</p> <pre><code>- (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; if (dummy) { free(dummy); dummy = nil; } } </code></pre> <p>This time app works longer. So far so good... Next step - make possible repeated memory freeing.</p> <pre><code>// Member variable NSMutableArray* _memoryWorkaround; // - (void)init int chunkCount = 100; int chunkSize = 1L * 1024L * 1024L; // 1 megabyte _memoryWorkaround = [[NSMutableArray alloc] initWithCapacity:chunkCount]; for (int i = 0; i &lt; chunkCount; i++) [_memoryWorkaround addObject:[NSValue valueWithPointer:malloc(chunkSize)]]; </code></pre> <p>Here it is - 100 chunks of memory by 1 megabyte allocated. This parameters is subject to revise.</p> <p>Now we can free up as much memory as needed:</p> <pre><code>- (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; if ([_memoryWorkaround count]) { NSValue* val = [_memoryWorkaround objectAtIndex:0]; free([val pointerValue]); [_memoryWorkaround removeObject:val]; } } </code></pre> <p>On exit free remaining:</p> <pre><code>- (void)dealloc { if ([_memoryWorkaround count]) { for (NSValue* val in _memoryWorkaround) free([val pointerValue]); [_memoryWorkaround removeAllObjects]; } [_memoryWorkaround release]; [super dealloc]; } </code></pre> <p>The last thing to do - is to fill buffer back to chunkCount with NSTimer one by one block.</p> <p>Seems crazy I know. Is better solution exists?</p>
 

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