metal &object c

https://developer.apple.com/documentation/metal/mtlcommandencoder/1458041-pushdebuggroup

PushDebugGroups

https://developer.apple.com/documentation/metal/mtlcommandencoder

这个encoder我之前在其它api里没见过就对应我tbdr里面提到的renderpass

有四种

`MTLRenderCommandEncoder`	An encoder used for graphics rendering tasks.
`MTLComputeCommandEncoder`	An encoder used for computational tasks.
`MTLBlitCommandEncoder`	An encoder used for memory management tasks.
`MTLParallelRenderCommandEncoder`	An encoder used for multiple graphics rendering tasks encoded in parallel.

https://developer.apple.com/documentation/metal/mtlcommandbuffer/1639924-gpustarttime

https://developer.apple.com/documentation/metal/mtlcommandbuffer/1442997-addcompletedhandler

https://developer.apple.com/documentation/metal/mtlcommandbuffer?language=objc

看了下cmdqueue和cmdbuffer和其它是一致的只是往cmdbuffer上写命令的时候需要用到以上四种不同encoder来写不同功能的命令并且它们可以

按照次序（一次只能用一种）多个encoder写到一块cmdbuffer上这样是不是我还是没法用cmd的

commandBuffer.addCompletedHandler { cb in

    let executionDuration = cb.gpuEndTime - cb.gpuStartTime

    /* ... */

}
拿到renderpass的时间。。。

巴特西