High memory usage in RNFI

[jochem725]

Hi,

I'm using SDWebImageWebPCoder with react-native-fast-image and I found that the memory usage is quite high. We use non-animated WebP images but it seems like RNFI uses SDAnimatedImageView to load the images. After profiling I found both _canvas and imageRef in safeAnimatedImageFrameAtIndex are retained. Which makes sense I guess since the canvas is reused for the animation. However for images this causes unnecessary memory usage.

As a temporary workaround I altered animatedImageFrameAtIndex so it releases the canvas after the final frame of the animation (which for an image is immediately)

- (UIImage *)animatedImageFrameAtIndex:(NSUInteger)index {
    UIImage *image;
    if (index >= _frameCount) {
        return nil;
    }
    SD_LOCK(_lock);
    image = [self safeAnimatedImageFrameAtIndex:index];
    SD_UNLOCK(_lock);
    
    if (index + 1 >= _frameCount) {
        CGContextRelease(_canvas);
        _canvas = NULL;
    }

    return image;
}

I don't think this is a great workaround since it impacts the behavior for animated WebP images (but it may be unnecessary to keep two copies of the image in memory?) so I wondered if there is another way to reduce the memory usage of WebP in SDWebImage and possibly improve RNFI.

[dreampiggy]

You can not do this. Because each frame does not guranteed to kept in the RAM. You assume after each frame was decoded, they're all cached., but actually, this is wrong.

Check our wiki for detail about the Animated Image Rerndering solution, you'll know how and why we design the animated image like this.

[dreampiggy]

There are one control behavior, the SDAnimatedImage.preloadAllFrames, this will actually load each frame into RAM, and does not decode them any more.

But, since this preload can be reverted using unloadAllFrames, so, we still can not release the CGContext.

A better solution is that for non-animated image, we does not use the SDAnimatedImage instance at all.

The init method in SDAnimatedImage should just check the frame count. If the frame count is 1, then we return nil, this can solve the problem from scratch.

Move this discussion to https://github.com/SDWebImage/SDWebImage is better.

[jochem725]

@dreampiggy Great, thank you for your quick response. I expected something like that was happening. I agree that a better solution would be to not use SDAnimatedImage in these cases.

[dreampiggy]

@jochem725 I release a quick fix via SDWebImageWebPCoder v0.3.1. Please update and have a check again for this.

[jochem725]

@dreampiggy v0.3.1 solves the issue, again thanks for the quick fix 😄

[dreampiggy]

@jochem725 SDWebImage 5.4.2 released as well. This WebPCoder can only fix for WebP, but not other thing like APNG/HEIF/AVIF format. It's better to upgrade to 5.4.2 version as well, which fix the issue from scratch.

[jochem725]

@dreampiggy I updated to SDWebImage 5.4.2, it works great.
Again, thanks for your quick response :)

[Stafox]

hey @dreampiggy . Looks like the issue still exists for ios < 14.0
Can reproduce on devices with ios 12 and ios 13 while trying to render static WebP images (I see huge memory usage which cause app crash due to memory).
On ios14 works fine because in 5.9.0 started used native coder implementation.

Any idea how to fix it?

[dreampiggy]

@Stafox Could you please provide your instrument profile result (https://developer.apple.com/documentation/xcode/improving_your_app_s_performance/reducing_your_app_s_memory_use/gathering_information_about_memory_use). And usage sample code ?

High memory usage != memory leak. There are different things.

And, for WebP images, the decoding algorithm of standard WebP need a canvas to draw animated images. For static image it does not need. So it may be some different cases between these animation/static.