CAMetalLayer nextDrawable 内存泄漏？

Question

我目前正在调查 iOS 中的内存泄漏。

我们有一个 ViewController 和该控制器的视图。
ViewController 当前被重复推送和弹出（用于调试目的）。
该视图包含一个 CAMetalLayer（class 方法 layerClass returns CAMetalLayer）和一个调用我的渲染方法的 CADisplayLink。
当我第一次调用 [metalLayer nextDrawable] 时，应用程序分配了大约 20MB。但是，当 ViewController 弹出时，只有一小部分被释放！我 100% 确定我没有保留周期或任何东西。

这是我的渲染初始化代码：

-(void)initializeRendering {
@autoreleasepool {
    id<MTLDevice> device = [[MetalRenderingSession sharedInstance] renderDevice];
    [self setCommandQueue:[device newCommandQueue]];
    CAMetalLayer* layer = static_cast<CAMetalLayer*>([self layer]);
    layer.device = device;
    layer.pixelFormat = MTLPixelFormatRGBA16Float;
    layer.framebufferOnly = true;
    layer.maximumDrawableCount = 2;
    layer.contentsScale = [self contentScaleFactor];
    [self setMetalLayer:layer];
    CGSize screenSize = [[UIScreen mainScreen] bounds].size;
    MTLTextureDescriptor* depthTextureDescriptor = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:MTLPixelFormatDepth32Float
        width:static_cast<NSUInteger>(screenSize.width) height:static_cast<NSUInteger>(screenSize.height) mipmapped:NO];
    [depthTextureDescriptor setUsage:MTLTextureUsageRenderTarget];
    id<MTLTexture> depthTexture = [device newTextureWithDescriptor:depthTextureDescriptor];
    [self setTextureDepth:depthTexture];
    [self updateOrientation:[[UIApplication sharedApplication] statusBarOrientation] size:[self frame].size];
    CADisplayLink* renderLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(render)];
    [renderLink setPreferredFramesPerSecond:30];
    [self setDisplayLink:renderLink];
    [renderLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
}
}

这是我的实际渲染代码：

-(void)render {
@autoreleasepool {
    dispatch_semaphore_wait([self renderCommandExecuting], DISPATCH_TIME_FOREVER);
    id<MTLCommandBuffer> commandBuffer = [[self commandQueue] commandBuffer];
    [[self commandQueue] insertDebugCaptureBoundary];

    //commenting next line and lines that use drawable makes memory leak disappear?
    id<CAMetalDrawable> drawable = [[self metalLayer] nextDrawable];
    id<MTLRenderCommandEncoder> encoder = [self createCommandEncoderfromCommandBuffer:commandBuffer andDrawable:drawable];
    //creating ViewPort here
    [encoder setViewport:viewport];

    //doing rendering here, but for debugging purpoeses i disabled rendering 
    [encoder endEncoding];
    [commandBuffer presentDrawable:drawable];

    [commandBuffer addCompletedHandler:^(id<MTLCommandBuffer> o) {
        dispatch_semaphore_signal([self renderCommandExecuting]);
    }];
    [commandBuffer commit];
    [commandBuffer waitUntilCompleted];
}
}

对我来说，似乎每个 CAMetalLayer，该应用都会创建一个 IOSurface ，但我怎样才能释放这些？

图表是阶梯式的，因为我在弹出视图控制器之前等待了 2 秒。 "steps" 当我按下视图控制器时出现。
我注意到只有 "VM:IOSurface" 爬上去，其余的保持不变。

这是我的清理代码（在视图中，从 viewWillDisappear 调用）：

-(void)stop {
[[self displayLink] setPaused:YES];
[[self displayLink] removeFromRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
//those are 4*4 float arrays, they are allocated in the view's init
free([self projectionMatrix]);
free([self viewMatrix]);
free([self modelMatrix]);
[self setCommandQueue:nil];
[self setMetalLayer:nil];
[self setTextureDepth:nil];
[self setRenderCommandExecuting:nil];
}

Answer 1

问题是 CADisplayLink。
您需要使用 -[[CADisplayLink]invalidate] 才能正确释放它。手动将其从 RunLoop 中移除是不够的。

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