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I have a set of labels that are placed within a set of UIViews inside a single UIScrollView. They have not been assigned an outlet. I am using Avenir Next Ultralight font for all of them, and they have varying sizes.

The main view has a single view controller which is nested in a navigation controller.

I was just running through a check of allocations and noticed that with this single view upon loading consumes about 10MB of memory of which 8MB are these labels, and when I go to the next view, that allocation remains live.

What could be causing this?

This is a snapshot from recording allocations. 

Snapshot    Timestamp   Growth  # Persistent
 VM: UILabel (CALayer)      7.90 MB 10
  0x5417000 00:02.950.428   1.23 MB  
  0x5553000 00:02.967.675   1.23 MB  
  0x568f000 00:02.978.283   1.23 MB  
  0x591d000 00:03.013.095   832.00 KB    
  0x57cb000 00:03.004.334   832.00 KB    
  0x50a7000 00:02.919.040   832.00 KB    
  0x5177000 00:02.937.076   832.00 KB    
  0x5347000 00:02.940.969   832.00 KB    
  0x52d3000 00:02.998.823   120.00 KB    
  0x52f1000 00:03.023.068   16.00 KB

This is the stack trace for the first one, and the rest are the same:

   0 libsystem_kernel.dylib mach_vm_allocate
   1 libsystem_kernel.dylib vm_allocate
   2 QuartzCore CA::Render::Shmem::new_shmem(unsigned long)
   3 QuartzCore CA::Render::Shmem::new_bitmap(unsigned int, unsigned int, unsigned int, unsigned int)
   4 QuartzCore CABackingStoreUpdate_
   5 QuartzCore ___ZN2CA5Layer8display_Ev_block_invoke
   6 QuartzCore x_blame_allocations
   7 QuartzCore CA::Layer::display_()
   8 QuartzCore CA::Layer::display_if_needed(CA::Transaction*)
   9 QuartzCore CA::Layer::layout_and_display_if_needed(CA::Transaction*)
  10 QuartzCore CA::Context::commit_transaction(CA::Transaction*)
  11 QuartzCore CA::Transaction::commit()
  12 UIKit -[UIApplication _reportAppLaunchFinished]
  13 UIKit -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:]
  14 UIKit -[UIApplication handleEvent:withNewEvent:]
  15 UIKit -[UIApplication sendEvent:]
  16 UIKit _UIApplicationHandleEvent
  17 GraphicsServices _PurpleEventCallback
  18 GraphicsServices PurpleEventCallback
  19 CoreFoundation __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__
  20 CoreFoundation __CFRunLoopDoSource1
  21 CoreFoundation __CFRunLoopRun
  22 CoreFoundation CFRunLoopRunSpecific
  23 CoreFoundation CFRunLoopRunInMode
  24 UIKit -[UIApplication _run]
  25 UIKit UIApplicationMain
  26 main 
  27 libdyld.dylib start

SOLUTION

Thought I would share how I managed to reduce this. It turns out that if you have labels which word wrap, and have a significant amount of empty space around the sides, and top and bottom, this adds to the memory required to display them. So, the solution is to reduce that space to an absolute minimum.

Here is the resulting snapshot:

Snapshot    Timestamp   Growth  # Persistent
 VM: UILabel (CALayer)      2.37 MB 9
  0x5321000 00:02.503.255   208.00 KB    
  0x5248000 00:02.474.045   392.00 KB    
  0x5087000 00:02.432.317   208.00 KB    
  0x50bb000 00:02.445.927   64.00 KB     
  0x5303000 00:02.498.137   120.00 KB    
  0x52aa000 00:02.481.354   292.00 KB    
  0x50cb000 00:02.449.625   180.00 KB    
  0x5355000 00:02.505.638   112.00 KB    
  0x50f9000 00:02.455.350   848.00 KB
Andriy
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user2916031
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  • This overhead does not strike me as excessive. Could you make a test without the labels? - Also, are the labels instantiated via storyboard? – Mundi Oct 24 '13 at 14:06
  • I did a test, and memory use was 8Mb less. Yes, via the labels are instantiated via storyboard. I did wind up doing another test, by reducing the size of each label to remove areas where the label is empty. Doing that with just two labels managed to reduce it by a 1.5Mb. – user2916031 Oct 24 '13 at 17:32
  • So as it turns out that was the issue. The empty space in the labels was increasing memory requirements significantly. I have managed to get the labels down to 2.4Mb. – user2916031 Oct 24 '13 at 17:50
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    OK - that means it was the *transparency*. The more transparent layers you have, the more memory intensive it is. Glad you resolved this. – Mundi Oct 24 '13 at 18:01
  • Thanks for your insight Mundi. – user2916031 Oct 25 '13 at 20:37

1 Answers1

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I am having the same issue. I will try what you suggested with the size. But, maybe changing the background color from clearColor could correct the issue as well.

Tim Walsh
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