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.