fi_efa(7)

NAME

fi_efa - The Amazon Elastic Fabric Adapter (EFA) Provider

OVERVIEW

The EFA provider supports the Elastic Fabric Adapter (EFA) device on Amazon EC2. EFA provides reliable and unreliable datagram send/receive with direct hardware access from userspace (OS bypass).

SUPPORTED FEATURES

The following features are supported:

Endpoint types
    The provider supports endpoint type FI_EP_DGRAM, and FI_EP_RDM on a new Scalable (unordered) Reliable Datagram protocol (SRD). SRD provides support for reliable datagrams and more complete error handling than typically seen with other Reliable Datagram (RD) implementations. The EFA provider provides segmentation, reassembly of out-of-order packets to provide send-after-send ordering guarantees to applications via its FI_EP_RDM endpoint.

RDM Endpoint capabilities
    The following data transfer interfaces are supported via the FI_EP_RDM endpoint: FI_MSG, FI_TAGGED, and FI_RMA. FI_SEND, FI_RECV, FI_DIRECTED_RECV, FI_MULTI_RECV, and FI_SOURCE capabilities are supported. The endpoint provides send-after-send guarantees for data operations. The FI_EP_RDM endpoint does not have a maximum message size.

DGRAM Endpoint capabilities
    The DGRAM endpoint only supports FI_MSG capability with a maximum message size of the MTU of the underlying hardware (approximately 8 KiB).

Address vectors
    The provider supports FI_AV_TABLE and FI_AV_MAP address vector types. FI_EVENT is unsupported.

Completion events
    The provider supports FI_CQ_FORMAT_CONTEXT, FI_CQ_FORMAT_MSG, and FI_CQ_FORMAT_DATA. FI_CQ_FORMAT_TAGGED is supported on the RDM endpoint. Wait objects are not currently supported.

Modes
    The provider requires the use of FI_MSG_PREFIX when running over the DGRAM endpoint, and requires FI_MR_LOCAL for all memory registrations on the DGRAM endpoint.

Memory registration modes
    The RDM endpoint does not require memory registration for send and receive operations, i.e. it does not require FI_MR_LOCAL. Applications may specify FI_MR_LOCAL in the MR mode flags in order to use descriptors provided by the application. The FI_EP_DGRAM endpoint only supports FI_MR_LOCAL.

Progress
    RDM and DGRAM endpoints support FI_PROGRESS_MANUAL. EFA erroneously claims the support for FI_PROGRESS_AUTO, despite not properly supporting automatic progress. Unfortunately, some Libfabric consumers also ask for FI_PROGRESS_AUTO when they only require FI_PROGRESS_MANUAL, and fixing this bug would break those applications. This will be fixed in a future version of the EFA provider by adding proper support for FI_PROGRESS_AUTO.

Threading
    The RDM endpoint supports FI_THREAD_SAFE, the DGRAM endpoint supports FI_THREAD_DOMAIN, i.e. the provider is not thread safe when using the DGRAM endpoint.

LIMITATIONS

The DGRAM endpoint does not support FI_ATOMIC interfaces. For RMA operations, completion events for RMA targets (FI_RMA_EVENT) is not supported. The DGRAM endpoint does not fully protect against resource overruns, so resource management is disabled for this endpoint (FI_RM_DISABLED).

No support for selective completions.

No support for counters for the DGRAM endpoint.

No support for inject.

When using FI_HMEM for either CUDA and Neuron buffers, the provider requires peer to peer transaction support between the EFA and the FI_HMEM device. Therefore, the FI_HMEM_P2P_DISABLED option is not supported by the EFA provider.

PROVIDER SPECIFIC ENDPOINT LEVEL OPTION

FI_OPT_EFA_RNR_RETRY
    Defines the number of RNR retry. The application can use it to reset RNR retry counter via the call to fi_setopt. Note that this option must be set before the endpoint is enabled. Otherwise, the call will fail. Also note that this option only applies to RDM endpoint.

RUNTIME PARAMETERS

FI_EFA_TX_SIZE
    Maximum number of transmit operations before the provider returns -FI_EAGAIN. For only the RDM endpoint, this parameter will cause transmit operations to be queued when this value is set higher than the default and the transmit queue is full.

FI_EFA_RX_SIZE
    Maximum number of receive operations before the provider returns -FI_EAGAIN.

FI_EFA_TX_IOV_LIMIT
    Maximum number of IOVs for a transmit operation.

FI_EFA_RX_IOV_LIMIT
    Maximum number of IOVs for a receive operation.

RUNTIME PARAMETERS SPECIFIC TO RDM ENDPOINT

These OFI runtime parameters apply only to the RDM endpoint.

FI_EFA_RX_WINDOW_SIZE
    Maximum number of MTU-sized messages that can be in flight from any single endpoint as part of long message data transfer.

FI_EFA_TX_QUEUE_SIZE
    Depth of transmit queue opened with the NIC. This may not be set to a value greater than what the NIC supports.

FI_EFA_RECVWIN_SIZE
    Size of out of order reorder buffer (in messages). Messages received out of this window will result in an error.

FI_EFA_CQ_SIZE
    Size of any cq created, in number of entries.

FI_EFA_MR_CACHE_ENABLE
    Enables using the mr cache and in-line registration instead of a bounce buffer for iov’s larger than max_memcpy_size. Defaults to true. When disabled, only uses a bounce buffer

FI_EFA_MR_MAX_CACHED_COUNT
    Sets the maximum number of memory registrations that can be cached at any time.

FI_EFA_MR_MAX_CACHED_SIZE
    Sets the maximum amount of memory that cached memory registrations can hold onto at any time.

FI_EFA_MAX_MEMCPY_SIZE
    Threshold size switch between using memory copy into a pre-registered bounce buffer and memory registration on the user buffer.

FI_EFA_MTU_SIZE
    Overrides the default MTU size of the device.

FI_EFA_RX_COPY_UNEXP
    Enables the use of a separate pool of bounce-buffers to copy unexpected messages out of the pre-posted receive buffers.

FI_EFA_RX_COPY_OOO
    Enables the use of a separate pool of bounce-buffers to copy out-of-order RTS packets out of the pre-posted receive buffers.

FI_EFA_MAX_TIMEOUT
    Maximum timeout (us) for backoff to a peer after a receiver not ready error.

FI_EFA_TIMEOUT_INTERVAL
    Time interval (us) for the base timeout to use for exponential backoff to a peer after a receiver not ready error.

FI_EFA_ENABLE_SHM_TRANSFER
    Enable SHM provider to provide the communication across all intra-node processes. SHM transfer will be disabled in the case where ptrace protection is turned on. You can turn it off to enable shm transfer.

FI_EFA_SHM_AV_SIZE
    Defines the maximum number of entries in SHM provider’s address vector.

FI_EFA_SHM_MAX_MEDIUM_SIZE
    Defines the switch point between small/medium message and large message. The message larger than this switch point will be transferred with large message protocol. NOTE: This parameter is now deprecated.

FI_EFA_INTER_MAX_MEDIUM_MESSAGE_SIZE
    The maximum size for inter EFA messages to be sent by using medium message protocol. Messages which can fit in one packet will be sent as eager message. Messages whose sizes are smaller than this value will be sent using medium message protocol. Other messages will be sent using CTS based long message protocol.

FI_EFA_FORK_SAFE
    Enable fork() support. This may have a small performance impact and should only be set when required. Applications that require to register regions backed by huge pages and also require fork support are not supported.

SEE ALSO

fabric(7), fi_provider(7), fi_getinfo(3)

AUTHORS
OpenFabrics.