---
title: gpuStartTime
framework: metal
role: symbol
role_heading: Instance Property
path: metal/mtlcommandbuffer/gpustarttime
---

# gpuStartTime

The host time, in seconds, when the GPU starts command buffer execution.

## Declaration

```swift
var gpuStartTime: CFTimeInterval { get }
```

## Discussion

Discussion You can calculate how much time the GPU spends running a command buffer by subtracting this value from gpuEndTime. Both values are relative to system mach time. The GPU start and end times remain 0.0 until the GPU finishes running the command buffer. Check this value after the waitUntilCompleted() method returns, or within a completion handler passed to the addCompletedHandler(_:) method.

## See Also

### Checking execution times on the GPU

- [gpuEndTime](metal/mtlcommandbuffer/gpuendtime.md)