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fi_mrail(7)			   @VERSION@			   fi_mrail(7)

NAME
       fi_mrail	- The Multi-Rail Utility Provider

OVERVIEW
       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.

REQUIREMENTS
   Requirements	for underlying provider
       mrail  provider requires	the underlying provider	to support the follow-
       ing capabilities	/ modes:

       o Buffered receive (FI_BUFFERED_RECV)

       o FI_SOURCE

       o FI_AV_TABLE

   Requirements	for applications
       Applications need to: * Support FI_MR_RAW MR mode bit to	 make  use  of
       FI_RMA  capability.   * Set FI_OFI_MRAIL_ADDR env variable (see RUNTIME
       PARAMETERS section below).

SUPPORTED FEATURES
       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  un-
       derlying	provider.

   Unsupported features
       The  following are the major libfabric features that are	not supported.
       Any other feature not listed in "Supported features" can	be assumed  as
       unsupported.

       o FI_ATOMIC

       o Scalable endpoints

       o Shared	contexts

       o FABRIC_DIRECT

       o Multicast

       o Triggered operations

FUNCTIONALITY OVERVIEW
       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.

RUNTIME	PARAMETERS
       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 ad-
	      dress, 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 as-
	      cending order of <max_size>.  Each pair indicated	the rail shar-
	      ing 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 in-
	      put as -1.

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

AUTHORS
       OpenFabrics.

Libfabric Programmer's Manual	  2020-04-14			   fi_mrail(7)

NAME | OVERVIEW | REQUIREMENTS | SUPPORTED FEATURES | FUNCTIONALITY OVERVIEW | RUNTIME PARAMETERS | SEE ALSO | AUTHORS

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