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Windows Driver Kit DDI reference (nf-d3dkmthk-d3dkmtcreatenativefence)

Description

The D3D runtime calls D3DKMTCreateNativeFence to create a native GPU fence object on a particular device.

Parameters

`unnamedParam1`

[in/out] Pointer to a D3DKMT_CREATENATIVEFENCE structure that describes the fence object to create.

Return value

D3DKMTCreateNativeFence returns STATUS_SUCCESS on successful creation. Otherwise it returns an NTSTATUS error code such as STATUS_INVALID_PARAMETER.

Remarks

The specified D3DDDI_NATIVEFENCE_TYPE dictates the type of native fence that the OS creates. These fences differ in functionality, performance characteristics, and storage requirements for CurrentValue and MonitoredValue. The following table shows these differences, where CVal stands for CurrentValue and MVal stands for MonitoredValue.

Type	CurrentValue	MonitoredValue	Supports Cross-process Sharing on CPU	Supports Cross-Adapter Sharing	UM CPUVA CVal	KM CPUVA CVal	GPU VA CVal	CMPVA CVal	UM MVal	KM MVal	GPU VA MVal	CMPVA MVal	Use Case
D3DDDI_NATIVEFENCE_TYPE_DEFAULT	Sysmem	Sysmem	Yes	Yes	ReadOnly	Read/Write	Read/Write	Read/Write	N/A	Write	ReadOnly (or Read/Write)	Read/Write	Application fences with reduced CPU interrupts. GPU waiter is unblocked without waking up CPU
D3DDDI_NATIVEFENCE_TYPE_DEFAULT (OPTIMIZED)	Sysmem	VRAM	Yes	Yes	ReadOnly	Read/Write	Read/Write	Read/Write	N/A	Write	ReadOnly (or Read/Write)	Read/Write	Same as Type 0 but with reduced PCI bus traffic as MVal reads are local to the GPU. The GPU signal command completes faster because of this reduced latency (throughput++).
D3DDDI_NATIVEFENCE_TYPE_INTRA_GPU	VRAM	VRAM	Yes	No	N/A	N/A	Read/Write	Read/Write	N/A	N/A	ReadOnly (or Read/Write)	Read/Write	Command buffer level (not application visible) synchronization within the same GPU. Read/Write to fence value (CVal) is local, so signal/unblock operations are fast.

D3DDDI_NATIVEFENCE_TYPE_DEFAULT
- Supported in Windows 11, version 24H2.
- This fence type supports all existing D3DKMT sync object Wait/Signal from CPU/GPU operations.
- Both CurrentValue and MonitoredValue storage for this fence type are allocated in system memory segment.
D3DDDI_NATIVEFENCE_TYPE_DEFAULT (Optimized)
- This capability is not currently supported by the OS.
- The optimized version of D3DDDI_NATIVEFENCE_TYPE_DEFAULT, in which the MonitoredValue storage can be allocated in VRAM, will speed up reads of MonitoredValue from the GPU engine.
- This optimization is not exposed to UMD. Instead, Dxgkrnl and KMD will decide whether the default fence type can be optimized by allocating MonitoredValue storage in VRAM.
- MonitoredValue storage allocated in VRAM may still be demoted to system memory if the system is under local memory pressure.
- If the OS supports this fence type, it sets SupportOptimizedDefaultFenceType to TRUE in the DXGKARGCB_FEATURE_NATIVEFENCE_CAPS_1 feature interface table. KMD is expected to query the feature interface table during driver initialization to determine this OS capability.
D3DDDI_NATIVEFENCE_TYPE_INTRA_GPU
- This capability is not currently supported by the OS.
- A D3DDDI_NATIVEFENCE_TYPE_INTRA_GPU fence doesn't support any CPU operations; that is, the OS doesn't allow user mode to queue wait and signals to this fence object.
- Hence, this type can't be used for DX application fences that must support CPU wait and signal semantics. This type is mainly used for internal UMD fences for synchronization between GPU engines. Creating this type as a D3DKMT native fence object provides visibility into these fences for tools such as GpuView and debugging.
- The supported segment for this fence must be a non-CPU visible local memory segment.
- Storage allocated in local memory may still be demoted to system memory if the system is under local memory pressure.
- If the OS supports this fence type, it sets SupportIntraGpuFenceType to TRUE in the DXGKARGCB_FEATURE_NATIVEFENCE_CAPS_1 feature interface table. KMD is expected to query the feature interface table during driver initialization to determine this OS capability.

For more information about native GPU fences, see Native GPU fence objects.

D3DKMTCreateNativeFence - NtDoc