Memory usage of CCTexture2D is doubled during load

cocos2d for iPhone » Programming » cocos2d support (graphics engine)

Memory usage of CCTexture2D is doubled during load

(16 posts) (9 voices)

Started 1 year ago by gaminghorror
Latest reply from goatlinks

Tags:

gaminghorror
Member
I noticed that loading a Texture consumes twice the memory it should but only while the texture is being loaded. I think i once read about it here but i'm not sure, which is why i'm posting this. It could also be a bug because i'm using 32-bit PNG in RGBA8888 format. I stepped through CCTexture2D and there is certainly no conversion being done.

When i load my texture atlases i ran into memory warnings. I have >20 MBs free in all cases, and am loading at most 14 MB of textures. Yet i got memory warnings. So i dove in to figure out what is going on.

I found out that each 1024x1024x32 PNG image takes twice the amount (8 MB) of memory but only while loading (in the same tick/step/frame), which is why i can't load my texture atlases all at once. After refactoring the texture loading into a scheduled method that runs at 0.1f interval i get the following output and no more memory warnings. Notice how each texture takes 8 MB during load, but when the next one is being loaded 4 MB have re-appeared.
```
Loading: Atlas_Tierteile1
 start KB = 27516.000000	final KB = 18972.000000	diff = 8544.000000
Loading: Atlas_Tierteile2
 start KB = 23144.000000	final KB = 15840.000000	diff = 7304.000000
Loading: Atlas_Tierteile3
 start KB = 19960.000000	final KB = 12196.000000	diff = 7764.000000
Loading: Atlas_Tierteile4
 start KB = 16632.000000	final KB = 15660.000000	diff = 972.000000
 start KB = 16180.000000	final KB = 16180.000000	diff = 0.000000
```
`

I wonder, did anyone else run into this problem and how did you solve it? I'm currently thinking about writing a scheduled texture loader that loads them in sequence. But maybe it's also possible to force freeing the memory within the same step, possibly by draining the autorelease pool somehow?

I also came across "async" methods, can i use those or are they simply for thread-safe texture loading?
Posted 1 year ago #
bradparks
Member

this sounds alot like the issue identified by @karl here:

http://www.cocos2d-iphone.org/forum/topic/3185#post-19889

but you were in that conversation too, so it's probably not it! but just in case ;-)

Posted 1 year ago #
zombie
Member

I would be interested,too, if the async loading of textures loads the textures after each other or all at once.

Posted 1 year ago #
CJ
Moderator

I think this is a known issue, and if it is to be fixed it should probably be fixed at the same time as this one:
http://code.google.com/p/cocos2d-iphone/issues/detail?id=697&sort=-id&colspec=ID%20Type%20Status%20Priority%20Milestone%20Component%20Owner%20Summary

Posted 1 year ago #
gaminghorror
Member

In any case i need a solution that loads textures one after the other with a delay, or by forcing the memory to be freed before loading the next texture.

Since reloading of textures needs to be done in applicationDidBecomeActive as well i'll have to find a solution, or make my own. If i come up with something i'll let you know.

Posted 1 year ago #
Karl
Member

The images take double the memory while loading because the UIImage being loaded by the OS takes memory, and the malloc'd ram the pixels are copied into also takes memory.

The only way to get around this is to load the pixels directly into your texture memory from a custom format, which is how I solved it (halved my load time, too!).

Posted 1 year ago #
zombie
Member

@Karl: Thats a great idea. Any chance you share your code or integrate it into cocos?

Posted 1 year ago #
CJ
Moderator

Any chance using libpng avoids this?

Posted 1 year ago #
riq
Key Master

@CJ: yes, I think that libpng solves this.

Posted 1 year ago #
zombie
Member

I do not really understand the memory consumption of our app...

I took a look at instruments (object allocations) but what I see does not make any sense. At startup the memory goes up to around 17MB. When leaving the loading Scene it goes down to 6 MB. In that next Scene we use two 1024 textures in 32bit so each one is 4MB and there is also loaded other stuff.

Posted 1 year ago #
javy
Member

"I think that libpng solves this."

If this is referring to the doubled memory use on loading, is there a plan to integrate libpng (or something similar) in image loading routines to reduce the memory use?

I could implement libpng in my own app, but I don't have a need to for another month or so. It would be nice to see something like it in Cocos.

Maybe cut-n-paste code someone more knowledgable could post? An addition to the Cocos cookbook?

Posted 1 year ago #
Karl
Member

@zombie: The code I have right now is too specific to the game I'm writing. Once I get this game into the app store I'll make it more generic.

libpng will help with the memory requirements, but you'll still have to do some bit twiddling to get the image to display properly. All pixel colors must be normalized to the alpha value. XCode does this automatically as part of the build process, but it results in PNG files that libpng won't recognize. You can turn this feature off, but then you'll have to do those modifications at runtime, which involves 4 floating point divisions and 7 floating point multiplications PER PIXEL.

Posted 1 year ago #
zombie
Member

I tested to load my images with libpng (like in the Texture2D test of Cocos2D. The memory consumption and load time was the same as for loading with the default Cocos2D method.

But as I mentioned all that memory stuff shown by Instruments does not make any sense to me :)

But my test showed me that loading asynchronously is way slower than loading synchronously.

Posted 1 year ago #
goatlinks
Member

Hey, I have run into the same issue. Our app runs mostly fine on an iPad 2, but crashes without warning on an iPad 1 whenever I start allocating new textures. I have run it through the Allocations Profiler in Instruments, and it looks like memory consumption spikes to around 30MB whenever I change scenes. I have tried to implement a staggered loading approach, where the scenes get loaded in a method that looks kinda like the following

- (void) loadTick { if (counter==0) { //Load Part 1 } else if (counter==1) { //Load Part 2 } else if (counter==2) { ... } else { //Signal Load Complete } counter++; }

This doesn't seem to change the memory use at all. I am not sure what is going on. I am diving into the Cocos Code now to try to figure it out, but I was wondering if there was any more insight along these lines since the last post.

BTW, I am using cocos v1.0.1

Posted 3 months ago #
crmagicxxx
Member

@goatlinks You're aware that previous scene isn't deallocated before you completely load next scene? So maybe your previous and next scene combine to more than your iPad can handle. If so, then use some "blank" intermediary scene to free memory and then go to next scene...

Posted 3 months ago #
goatlinks
Member

Hey, yeah I already have a LoadingScene class that allows the previous scene to be freed before starting to load the new scene. I think I am going to write a class that will load textures asynchronously and makes sure any extra copies are released before attempting to load the next. I'm still pouring through the cocos source to make sure there isn't already a way around this mess.

Thanks for the tip though. I only recently ran into the scene stacking issue.

Posted 3 months ago #

RSS feed for this topic

Reply

You must log in to post.