fi_mrail - Man Page

The mrail provider (ofi_mrail) is an utility provider that layers over an underlying provider to enable the use of multiple network ports (rails). This increases the total available bandwidth of an underlying provider. The current status of mrail provider is experimental - not all libfabric features are supported and performance is not guaranteed.

Endpoint types

The provider supports only FI_EP_RDM.

Endpoint capabilities

The following data transfer interface is supported: FI_MSG, FI_TAGGED, FI_RMA.

# LIMITATIONS

Limitations of the underlying provider may show up as that of mrail provider. mrail provider doesn’t allow pass-through of any mode bits to the underlying provider.

For messages (FI_MSG, FI_TAGGED), the provider uses different policies to send messages over one or more rails based on message size (See FI_OFI_MRIAL_CONFIG in the Runtime Parameters section). Ordering is guaranteed through the use of sequence numbers.

For RMA, the data is striped equally across all rails.

The ofi_mrail provider checks for the following environment variables.

FI_OFI_MRAIL_ADDR

Comma delimited list of individual rail addresses. Each address can be an address in FI_ADDR_STR format, a host name, an IP address, or a netdev interface name.

FI_OFI_MRAIL_ADDR_STRC

Deprecated. Replaced by FI_OFI_MRAIL_ADDR.

FI_OFI_MRAIL_CONFIG

Comma separated list of <max_size>:<policy> pairs, sorted in ascending order of <max_size>. Each pair indicated the rail sharing policy to be used for messages up to the size <max_size> and not covered by all previous pairs. The value of <policy> can be fixed (a fixed rail is used), round-robin (one rail per message, selected in round-robin fashion), or striping (striping across all the rails). The default configuration is 16384:fixed,ULONG_MAX:striping. The value ULONG_MAX can be input as -1.

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

OpenFabrics.