1fi_direct(7)                   Libfabric v1.17.0                  fi_direct(7)
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NAME

6       fi_direct - Direct fabric provider access
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SYNOPSIS

9              -DFABRIC_DIRECT
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11              #define FABRIC_DIRECT
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13       Fabric  direct provides a mechanism for applications to compile against
14       a specific fabric providers without going through the libfabric  frame‐
15       work  or  function vector tables.  This allows for extreme optimization
16       via function inlining at the cost of supporting multiple  providers  or
17       different versions of the same provider.
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DESCRIPTION

20       The use of fabric direct is intended only for applications that require
21       the absolute minimum software latency, and are  willing  to  re-compile
22       for specific fabric hardware.  Providers that support fabric direct im‐
23       plement their own versions of the static inline calls which are  define
24       in the libfabric header files, define selected enum values, and provide
25       defines for compile-time optimizations.   Applications  can  then  code
26       against  the  standard  libfabric  calls, but link directly against the
27       provider calls by defining FABRIC_DIRECT as part of their build.
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29       In general, the use of  fabric  direct  does  not  require  application
30       source code changes, and, instead, is limited to the build process.
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32       Providers  supporting  fabric  direct must install `direct' versions of
33       all libfabric header files.  For  convenience,  the  libfabric  sources
34       contain  sample  header  files that may be modified by a provider.  The
35       `direct' header file names have `fi_direct'  as  their  prefix:  fi_di‐
36       rect.h, fi_direct_endpoint.h, etc.
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38       Direct  providers  are prohibited from overriding or modifying existing
39       data structures.   However,  provider  specific  extensions  are  still
40       available.   In  addition to provider direct function calls to provider
41       code, a fabric direct provider may define zero of more of the following
42       capability  definitions.  Applications can check for these capabilities
43       in order to optimize code paths at compile time, versus relying on run-
44       time checks.
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CAPABILITY DEFINITIONS

47       In  order  that  application code may be optimized during compile time,
48       direct providers must provide definitions for various capabilities  and
49       modes, if those capabilities are supported.  The following #define val‐
50       ues may be used by an application to test for provider support of  sup‐
51       ported features.
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53       FI_DIRECT_CONTEXT
54              The  provider  sets  FI_CONTEXT or FI_CONTEXT2 for fi_info:mode.
55              See fi_getinfo for additional details.   When  FI_DIRECT_CONTEXT
56              is  defined,  applications should use struct fi_context in their
57              definitions, even if FI_CONTEXT2 is set.
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59       FI_DIRECT_LOCAL_MR
60              The provider sets FI_LOCAL_MR for fi_info:mode.  See  fi_getinfo
61              for additional details.
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SEE ALSO

64       fi_getinfo(3), fi_endpoint(3), fi_domain(3)
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AUTHORS

67       OpenFabrics.
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71Libfabric Programmer’s Manual     2022-12-11                      fi_direct(7)
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