Trouble understanding resource loading. Can someone enlighten me?

Question

Hi,

so I am working on this game that has a randomly generated world. It also has different themes for the world. Only one theme is being used at the same time in the game. I put all theme files into the reosurces folder. This is the file structure I am using:

 Assets/
 - Resources/
 - - Themes/
 - - - DesertTheme/
 - - - - Materials/
 - - - - Prefabs/
 - - - - Options/
 - - - WinterTheme/
 - - - - Materials/
 - - - - Prefabs/
 - - - - Options/
 - - - AnotherTheme/
 - - - - ...
 - - - - and so on...

My problem with that is: All files are constantly loaded into memory. I want to only have the currently used theme in memory. If i for testing remove all themes but the one that is active from the resources folder, I will save 60mb on my iPhone. Which is a lot.

This is how I am loading the theme stuff:

 // Load all prefabs of the desert theme
 Resources.LoadAll("Themes/Desert/Prefabs");

 // Load specific material
 Resources.Load("Themes/Desert/Materials/sand");

I tried Resources.UnloadUnusedAssets() but there was no effect.

How do I load only the themes I am actually using into memory? What might have caused those files to load?

Answer 1

Answer by Caruzo · Oct 29, 2015 at 08:43 PM

I can see a difference between your first and second script. In the second script you Load /Themes/Desert??? Since there is no Desert folder (it should be DesertTheme) it might do buggy things. Try to follow the pathing correctly! I am almost sure this is not the solution but might be something that can help your issue :)

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0xsven · Oct 29, 2015 at 11:37 PM 0

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That's all pseudo code! I will correct it

Answer 2

Answer by Statement · Oct 29, 2015 at 09:33 PM

Did you try this on device? Can you confirm the objects are loaded in memory? What is your method to measure that? The editor can load keep resources loaded sometimes, if you were looking at it there.

If Resources.UnloadUnusedAssets have no effect it means you have a reference to it somewhere

Make sure that there isn't any reference to the objects left lingering anywhere as described below. If you add them to a list etc, clear that list before calling UnloadUnusedAssets. Did you register an event handler on one of the objects? Clear that too. And so on.

http://docs.unity3d.com/ScriptReference/Resources.UnloadUnusedAssets.html

An asset is deemed to be unused if it isn't reached after walking the whole game object hierarchy, including script components. Static variables are also examined.

The script excecution stack, however, is not examined so an asset referenced only from within the script stack will be unloaded and, if necessary, loaded back in the next time one of its properties or methods is used. This requires extra care for assets which have been modified in memory.

http://docs.unity3d.com/Manual/LoadingResourcesatRuntime.html

If you want to destroy scene objects loaded using Resources.Load() prior to loading another level, call Object.Destroy() on them. To release assets, use Resources.UnloadUnusedAssets().

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0xsven · Oct 30, 2015 at 12:46 PM 0

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The method of measuring is comparing these two scenarios: a) Deploy the app with 15 themes to my iPhone. Play with theme x for one minute and check XCode's profiler for memory usage: 200 MB b) Remove all themes but theme x and deploy to iPhone. Play theme x for one minute and check XCode's profiler for memory usage: 140 MB (even CPU usage is much lower)

In both scenarios theme x is loaded using Resources.Load(path-to-theme). I do that several times for several subfolders of the theme like described in the post. Never are the other themes loaded in my code! So they don't appear in the GameObject hierarchy.

My best guess is that I use some function that loads everything without me knowing it. Or that I configured the app to do so without knowing.

Statement · Oct 30, 2015 at 01:26 PM 0

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@0xsven: I don't want to jump to any speculations yet (I have a vague guessplination I'd rather avoid going into before eliminating straight forward, testable ideas).

Let's for simplicity sake say that you load 3 textures, called A, B and C.

 void LoadTheme(string theme)
 {        
     a = Resources.Load<Texture2D>(theme + "/A");
     b = Resources.Load<Texture2D>(theme + "/B");
     c = Resources.Load<Texture2D>(theme + "/C");
     StartCoroutine(UnloadUnusedAssets());
 }
 
 IEnumerator UnloadUnusedAssets()
 {
     yield return Resources.UnloadUnusedAssets();
     PrintLoadedTextures();
 }
 
 void PrintLoadedTextures()
 {
     StringBuilder sb = new StringBuilder();
     sb.AppendLine("Currently loaded textures");
     foreach (var t in FindObjectsOfType<Texture2D>())
     {
         sb.Append("  "); sb.AppendLine(t.name);
     }
     print(sb);
 }

Do you still see the previous textures as loaded?

Example:

 LoadTheme("Foo");
 // You should see A, B and C among the loaded textures
 
 // ...... some time passes ....
 
 LoadTheme("Bar");
 // You should see A, B and C among the loaded textures, but not twice!
 // If your see A, B, C, A, B, C then you still have a reference to the textures somewhere! (One set of textures is from the theme Foo, the other from Bar).

If you notice that your textures are still there, use the memory profiler to figure out which object is holding on to it.

Here's an example of finding out why "DeselectOnClick" is kept loaded. Open profiler, go to memory row, select detailed mode, take a sample, find & select DeselectOnClick under Assets/MonoScript and finally get a list of objects holding on to it.

However if your textures are completely gone and you still use memory, it could be something else. Try to use the memory profiler to figure out what you have loaded.

0xsven Statement · Oct 30, 2015 at 03:16 PM 0

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The textures are completely gone when loading a new theme!

Statement 0xsven · Oct 31, 2015 at 02:18 AM 0

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And still using memory? Well that sucks. I don't know for certain why Instruments (I guess that's what you're using to profile outside of Unity) says it uses the memory you've given back. Perhaps Unity or iOS is holding on to file(s) in a cache that can be evicted if you have to dump memory, but it's a guessplanation. Another guessplanation would be that Unity keeps sharedresources.asset in memory, but again that sounds dumb if it stays there forever and you have no direct control over that. If it really bothers you, I guess you could try loading and unloading them in as asset bundles. Please do make emphasis on "try", as I really wouldn't think it should solve anything. It's more a method of exhausting what you can do on your end.

If you can't get a hang of it and you produce out of memory crashes, I'd recommend to make a reproducible project that only load/unload assets in a way that clearly and simply demonstrates the issue without dependencies on anything else. Submit a bug report/share download link here and possibly contact support to see if they have any suggestions on how you can work around it, or where you may be going wrong.

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Trouble understanding resource loading. Can someone enlighten me?

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