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Peer Device Memory Access

\brief peer device memory access functions of the CUDA runtime API (cuda_runtime_api.h)

This section describes the peer device memory access functions of the CUDA runtime application programming interface.

cudaError_t cudaDeviceCanAccessPeer (int * canAccessPeer, int device, int peerDevice)

Returns in *canAccessPeer a value of 1 if device device is capable of directly accessing memory from peerDevice and 0 otherwise. If direct access of peerDevice from device is possible, then access may be enabled by calling cudaDeviceEnablePeerAccess().

Parameters:

canAccessPeer - Returned access capability
device - Device from which allocations on peerDevice are to be directly accessed.
peerDevice - Device on which the allocations to be directly accessed by device reside.

Returns:

cudaSuccess, cudaErrorInvalidDevice

Note:

Note that this function may also return error codes from previous, asynchronous launches.

See also:

cudaDeviceEnablePeerAccess, cudaDeviceDisablePeerAccess, cuDeviceCanAccessPeer

cudaError_t cudaDeviceDisablePeerAccess (int peerDevice)

Returns cudaErrorPeerAccessNotEnabled if direct access to memory on peerDevice has not yet been enabled from the current device.

Parameters:

peerDevice - Peer device to disable direct access to

Returns:

cudaSuccess, cudaErrorPeerAccessNotEnabled, cudaErrorInvalidDevice

Note:

Note that this function may also return error codes from previous, asynchronous launches.

See also:

cudaDeviceCanAccessPeer, cudaDeviceEnablePeerAccess, cuCtxDisablePeerAccess

cudaError_t cudaDeviceEnablePeerAccess (int peerDevice, unsigned int flags)

On success, all allocations from peerDevice will immediately be accessible by the current device. They will remain accessible until access is explicitly disabled using cudaDeviceDisablePeerAccess() or either device is reset using cudaDeviceReset().

Note that access granted by this call is unidirectional and that in order to access memory on the current device from peerDevice, a separate symmetric call to cudaDeviceEnablePeerAccess() is required.

Note that there are both device-wide and system-wide limitations per system configuration, as noted in the CUDA Programming Guide under the section 'Peer-to-Peer Memory Access'.

Returns cudaErrorInvalidDevice if cudaDeviceCanAccessPeer() indicates that the current device cannot directly access memory from peerDevice.

Returns cudaErrorPeerAccessAlreadyEnabled if direct access of peerDevice from the current device has already been enabled.

Returns cudaErrorInvalidValue if flags is not 0.

Parameters:

peerDevice - Peer device to enable direct access to from the current device
flags - Reserved for future use and must be set to 0

Returns:

cudaSuccess, cudaErrorInvalidDevice, cudaErrorPeerAccessAlreadyEnabled, cudaErrorInvalidValue

Note:

Note that this function may also return error codes from previous, asynchronous launches.

See also:

cudaDeviceCanAccessPeer, cudaDeviceDisablePeerAccess, cuCtxEnablePeerAccess

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