NAME

       fi_direct - Direct fabric provider access

SYNOPSIS

              -DFABRIC_DIRECT

              #define FABRIC_DIRECT

       Fabric  direct  provides a mechanism for applications to compile against a specific fabric
       providers without going through the libfabric framework or function vector  tables.   This
       allows  for  extreme optimization via function inlining at the cost of supporting multiple
       providers or different versions of the same provider.

DESCRIPTION

       The use of fabric direct is intended only  for  applications  that  require  the  absolute
       minimum  software  latency,  and  are  willing to re-compile for specific fabric hardware.
       Providers that support fabric direct implement their own versions  of  the  static  inline
       calls  which  are  define  in the libfabric header files, define selected enum values, and
       provide defines for compile-time optimizations.  Applications can then  code  against  the
       standard  libfabric  calls,  but  link  directly  against  the  provider calls by defining
       FABRIC_DIRECT as part of their build.

       In general, the use of fabric direct does not require  application  source  code  changes,
       and, instead, is limited to the build process.

       Providers  supporting fabric direct must install 'direct' versions of all libfabric header
       files.  For convenience, the libfabric sources contain sample header  files  that  may  be
       modified  by a provider.  The 'direct' header file names have 'fi_direct' as their prefix:
       fi_direct.h, fi_direct_endpoint.h, etc.

       Direct providers are prohibited from overriding or  modifying  existing  data  structures.
       However, provider specific extensions are still available.  In addition to provider direct
       function calls to provider code, a fabric direct provider may define zero of more  of  the
       following  capability definitions.  Applications can check for these capabilities in order
       to optimize code paths at compile time, versus relying on run-time checks.

CAPABILITY DEFINITIONS

       In order that application code may be optimized during compile time, direct providers must
       provide  definitions  for  various  capabilities  and  modes,  if  those  capabilities are
       supported.  The following #define values may  be  used  by  an  application  to  test  for
       provider support of supported features.

       FI_DIRECT_CONTEXT  :  The  provider  sets FI_CONTEXT or FI_CONTEXT2 for fi_info:mode.  See
       fi_getinfo for additional details.  When FI_DIRECT_CONTEXT is defined, applications should
       use struct fi_context in their definitions, even if FI_CONTEXT2 is set.

       FI_DIRECT_LOCAL_MR  :  The provider sets FI_LOCAL_MR for fi_info:mode.  See fi_getinfo for
       additional details.

SEE ALSO

       fi_getinfo(3), fi_endpoint(3), fi_domain(3)

AUTHORS

       OpenFabrics.