如何释放 MTLBuffer 和 MTLTexture

Question

我知道如何创建 MTLBuffer 和/或 MTLTexture，但如何在不再需要这些资源时释放 GPU 内存？

Answer 1

MTLBuffer 和 MTLTexture 是 Objective-C 对象，因此引用计数。如果您在 Objective-C 项目中使用自动引用计数或通过 Swift 使用 Metal，只需确保您不再持有对缓冲区或纹理的引用即可释放任何相关的硬件资源。

let texture: MTLTexture? = device.newTexture(with: descriptor)
texture = nil // <- resources will be released

可以通过在将 nil 分配给 texture 时逐步执行相关程序集来确认这一点，这首先会导致我们 [MTLDebugTexture dealloc]

MetalTools`-[MTLDebugTexture dealloc]:
    ...
->  0x100af569e <+34>: call   0x100af87ee               ; symbol stub for: objc_msgSendSuper2
    0x100af56a3 <+39>: add    rsp, 0x10
    0x100af56a7 <+43>: pop    rbp
    0x100af56a8 <+44>: ret

...并通过 [MTLToolsObject dealloc]

MetalTools`-[MTLToolsObject dealloc]:
    0x100ac6c7a <+0>:   push   rbp
    0x100ac6c7b <+1>:   mov    rbp, rsp
    0x100ac6c7e <+4>:   push   r14
    ...

...并通过 GeForceMTLDriver

GeForceMTLDriver`___lldb_unnamed_symbol1095$$GeForceMTLDriver:
->  0x7fffd2e57b14 <+0>:  push   rbp
    0x7fffd2e57b15 <+1>:  mov    rbp, rsp

一直以来，通过各种dealloc方法释放任何资源。

Answer 2

如果您正在使用自动引用计数，正如接受的答案所说，只需设置为零。

但是如果你使用手动引用计数，Metal有两种动态分配的资源(MTLBuffer && MTLTexture)，你可以释放他们在下面的方式。

id<MTLDevice> m_Device = MTLCreateSystemDefaultDevice();
// allocate Buffer
NSUInteger BufferLength = 100;
id<MTLBuffer> m_Buffer = [m_Device newBufferWithLength:BufferLength options:0]; 

// allocate Texture
MTLTextureDescriptor *shadowTextureDesc = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat: MTLPixelFormatDepth32Float width: 1024 height: 1024 mipmapped: NO];
id<MTLTexture> m_Texture = [m_Device newTextureWithDescriptor:shadowTextureDesc];

// release Buffer
[m_Buffer setPurgeableState:MTLPurgeableStateEmpty]; 
[m_Buffer release];

// release Texture
[m_Texture setPurgeableState:MTLPurgeableStateEmpty];
[m_Texture release];

关于setPurgeableState，可以参考link(https://developer.apple.com/documentation/metal/mtlresource/1515898-setpurgeablestate)

如何释放 MTLBuffer 和 MTLTexture

How to deallocate a MTLBuffer and MTLTexture

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