1fi_endpoint(3)                 Libfabric v1.10.0                fi_endpoint(3)
2
3
4

NAME

6       fi_endpoint - Fabric endpoint operations
7
8       fi_endpoint / fi_scalable_ep / fi_passive_ep / fi_close
9              Allocate or close an endpoint.
10
11       fi_ep_bind
12              Associate  an  endpoint  with  hardware resources, such as event
13              queues, completion queues, counters, address vectors, or  shared
14              transmit/receive contexts.
15
16       fi_scalable_ep_bind
17              Associate a scalable endpoint with an address vector
18
19       fi_pep_bind
20              Associate a passive endpoint with an event queue
21
22       fi_enable
23              Transitions an active endpoint into an enabled state.
24
25       fi_cancel
26              Cancel a pending asynchronous data transfer
27
28       fi_ep_alias
29              Create an alias to the endpoint
30
31       fi_control
32              Control endpoint operation.
33
34       fi_getopt / fi_setopt
35              Get or set endpoint options.
36
37       fi_rx_context / fi_tx_context / fi_srx_context / fi_stx_context
38              Open a transmit or receive context.
39
40       fi_tc_dscp_set / fi_tc_dscp_get
41              Convert between a DSCP value and a network traffic class
42
43       fi_rx_size_left / fi_tx_size_left (DEPRECATED)
44              Query the lower bound on how many RX/TX operations may be posted
45              without an operation returning -FI_EAGAIN.  This functions  have
46              been  deprecated  and will be removed in a future version of the
47              library.
48

SYNOPSIS

50              #include <rdma/fabric.h>
51
52              #include <rdma/fi_endpoint.h>
53
54              int fi_endpoint(struct fid_domain *domain, struct fi_info *info,
55                  struct fid_ep **ep, void *context);
56
57              int fi_scalable_ep(struct fid_domain *domain, struct fi_info *info,
58                  struct fid_ep **sep, void *context);
59
60              int fi_passive_ep(struct fi_fabric *fabric, struct fi_info *info,
61                  struct fid_pep **pep, void *context);
62
63              int fi_tx_context(struct fid_ep *sep, int index,
64                  struct fi_tx_attr *attr, struct fid_ep **tx_ep,
65                  void *context);
66
67              int fi_rx_context(struct fid_ep *sep, int index,
68                  struct fi_rx_attr *attr, struct fid_ep **rx_ep,
69                  void *context);
70
71              int fi_stx_context(struct fid_domain *domain,
72                  struct fi_tx_attr *attr, struct fid_stx **stx,
73                  void *context);
74
75              int fi_srx_context(struct fid_domain *domain,
76                  struct fi_rx_attr *attr, struct fid_ep **rx_ep,
77                  void *context);
78
79              int fi_close(struct fid *ep);
80
81              int fi_ep_bind(struct fid_ep *ep, struct fid *fid, uint64_t flags);
82
83              int fi_scalable_ep_bind(struct fid_ep *sep, struct fid *fid, uint64_t flags);
84
85              int fi_pep_bind(struct fid_pep *pep, struct fid *fid, uint64_t flags);
86
87              int fi_enable(struct fid_ep *ep);
88
89              int fi_cancel(struct fid_ep *ep, void *context);
90
91              int fi_ep_alias(struct fid_ep *ep, struct fid_ep **alias_ep, uint64_t flags);
92
93              int fi_control(struct fid *ep, int command, void *arg);
94
95              int fi_getopt(struct fid *ep, int level, int optname,
96                  void *optval, size_t *optlen);
97
98              int fi_setopt(struct fid *ep, int level, int optname,
99                  const void *optval, size_t optlen);
100
101              uint32_t fi_tc_dscp_set(uint8_t dscp);
102
103              uint8_t fi_tc_dscp_get(uint32_t tclass);
104
105              DEPRECATED ssize_t fi_rx_size_left(struct fid_ep *ep);
106
107              DEPRECATED ssize_t fi_tx_size_left(struct fid_ep *ep);
108

ARGUMENTS

110       fid    On creation, specifies a fabric  or  access  domain.   On  bind,
111              identifies  the  event  queue, completion queue, counter, or ad‐
112              dress vector to bind to the endpoint.  In other  cases,  it's  a
113              fabric identifier of an associated resource.
114
115       info   Details  about  the  fabric interface endpoint to be opened, ob‐
116              tained from fi_getinfo.
117
118       ep     A fabric endpoint.
119
120       sep    A scalable fabric endpoint.
121
122       pep    A passive fabric endpoint.
123
124       context
125              Context associated with the endpoint or asynchronous operation.
126
127       index  Index to retrieve a specific transmit/receive context.
128
129       attr   Transmit or receive context attributes.
130
131       flags  Additional flags to apply to the operation.
132
133       command
134              Command of control operation to perform on endpoint.
135
136       arg    Optional control argument.
137
138       level  Protocol level at which the desired option resides.
139
140       optname
141              The protocol option to read or set.
142
143       optval The option value that was read or to set.
144
145       optlen The size of the optval buffer.
146

DESCRIPTION

148       Endpoints are transport level communication  portals.   There  are  two
149       types  of endpoints: active and passive.  Passive endpoints belong to a
150       fabric domain and are most often used to listen for incoming connection
151       requests.   However, a passive endpoint may be used to reserve a fabric
152       address that can be granted to an active  endpoint.   Active  endpoints
153       belong to access domains and can perform data transfers.
154
155       Active  endpoints may be connection-oriented or connectionless, and may
156       provide data reliability.  The data  transfer  interfaces  --  messages
157       (fi_msg),  tagged  messages  (fi_tagged),  RMA  (fi_rma),  and  atomics
158       (fi_atomic) -- are associated with active endpoints.  In basic configu‐
159       rations, an active endpoint has transmit and receive queues.  In gener‐
160       al, operations that generate traffic on the fabric are  posted  to  the
161       transmit  queue.   This  includes  all RMA and atomic operations, along
162       with sent messages and sent tagged messages.  Operations that post buf‐
163       fers for receiving incoming data are submitted to the receive queue.
164
165       Active  endpoints are created in the disabled state.  They must transi‐
166       tion into an enabled state before accepting data  transfer  operations,
167       including  posting  of  receive buffers.  The fi_enable call is used to
168       transition an active endpoint into an enabled  state.   The  fi_connect
169       and  fi_accept  calls will also transition an endpoint into the enabled
170       state, if it is not already active.
171
172       In order to transition an endpoint into an enabled state,  it  must  be
173       bound  to one or more fabric resources.  An endpoint that will generate
174       asynchronous completions, either through data  transfer  operations  or
175       communication  establishment  events,  must be bound to the appropriate
176       completion queues or event queues, respectively, before being  enabled.
177       Additionally,  endpoints  that  use  manual progress must be associated
178       with relevant completion queues or  event  queues  in  order  to  drive
179       progress.   For  endpoints  that  are only used as the target of RMA or
180       atomic operations, this means binding  the  endpoint  to  a  completion
181       queue  associated  with receive processing.  Unconnected endpoints must
182       be bound to an address vector.
183
184       Once an endpoint has been activated, it may be associated with  an  ad‐
185       dress  vector.   Receive  buffers  may be posted to it and calls may be
186       made to connection establishment  routines.   Connectionless  endpoints
187       may also perform data transfers.
188
189       The behavior of an endpoint may be adjusted by setting its control data
190       and protocol options.  This allows the underlying provider to  redirect
191       function  calls to implementations optimized to meet the desired appli‐
192       cation behavior.
193
194       If an endpoint experiences a critical error, it  will  transition  back
195       into  a disabled state.  Critical errors are reported through the event
196       queue associated with the EP.  In certain cases,  a  disabled  endpoint
197       may  be  re-enabled.   The  ability  to transition back into an enabled
198       state is provider specific and depends on the type of  error  that  the
199       endpoint  experienced.   When  an endpoint is disabled as a result of a
200       critical error, all pending operations are discarded.
201
202   fi_endpoint / fi_passive_ep / fi_scalable_ep
203       fi_endpoint allocates a new active endpoint.  fi_passive_ep allocates a
204       new  passive  endpoint.   fi_scalable_ep allocates a scalable endpoint.
205       The properties and behavior of the endpoint are defined  based  on  the
206       provided  struct  fi_info.   See  fi_getinfo  for additional details on
207       fi_info.  fi_info flags that control the operation of an  endpoint  are
208       defined below.  See section SCALABLE ENDPOINTS.
209
210       If  an active endpoint is allocated in order to accept a connection re‐
211       quest, the fi_info parameter must be the same as the fi_info  structure
212       provided with the connection request (FI_CONNREQ) event.
213
214       An  active endpoint may acquire the properties of a passive endpoint by
215       setting the fi_info handle field to the  passive  endpoint  fabric  de‐
216       scriptor.   This  is  useful  for applications that need to reserve the
217       fabric address of an endpoint prior to knowing if the endpoint will  be
218       used  on the active or passive side of a connection.  For example, this
219       feature is useful for simulating socket semantics.  Once an active end‐
220       point  acquires  the properties of a passive endpoint, the passive end‐
221       point is no longer bound to any fabric resources and must no longer  be
222       used.  The user is expected to close the passive endpoint after opening
223       the active endpoint in order to free up any  lingering  resources  that
224       had been used.
225
226   fi_close
227       Closes an endpoint and release all resources associated with it.
228
229       When closing a scalable endpoint, there must be no opened transmit con‐
230       texts, or receive contexts associated with the scalable  endpoint.   If
231       resources are still associated with the scalable endpoint when attempt‐
232       ing to close, the call will return -FI_EBUSY.
233
234       Outstanding operations posted to the endpoint when fi_close  is  called
235       will be discarded.  Discarded operations will silently be dropped, with
236       no completions reported.  Additionally, a provider may  discard  previ‐
237       ously  completed  operations  from  the associated completion queue(s).
238       The behavior to discard completed operations is provider specific.
239
240   fi_ep_bind
241       fi_ep_bind is used to associate an endpoint with  other  allocated  re‐
242       sources,  such  as  completion queues, counters, address vectors, event
243       queues, shared contexts, and memory regions.  The type of objects  that
244       must be bound with an endpoint depend on the endpoint type and its con‐
245       figuration.
246
247       Passive endpoints must be bound with an  EQ  that  supports  connection
248       management  events.  Connectionless endpoints must be bound to a single
249       address vector.  If an endpoint is using a shared transmit  and/or  re‐
250       ceive context, the shared contexts must be bound to the endpoint.  CQs,
251       counters, AV, and shared contexts must be  bound  to  endpoints  before
252       they are enabled either explicitly or implicitly.
253
254       An endpoint must be bound with CQs capable of reporting completions for
255       any asynchronous operation initiated on the endpoint.  For example,  if
256       the  endpoint  supports  any  outbound  transfers (sends, RMA, atomics,
257       etc.), then it must be bound to a  completion  queue  that  can  report
258       transmit  completions.  This is true even if the endpoint is configured
259       to suppress successful completions, in order that operations that  com‐
260       plete in error may be reported to the user.
261
262       An  active  endpoint  may  direct asynchronous completions to different
263       CQs,  based  on  the  type  of  operation.   This  is  specified  using
264       fi_ep_bind flags.  The following flags may be OR'ed together when bind‐
265       ing an endpoint to a completion domain CQ.
266
267       FI_RECV
268              Directs the notification of inbound data transfers to the speci‐
269              fied  completion  queue.  This includes received messages.  This
270              binding automatically includes FI_REMOTE_WRITE, if applicable to
271              the endpoint.
272
273       FI_SELECTIVE_COMPLETION
274              By default, data transfer operations write CQ completion entries
275              into the associated completion queue after they have successful‐
276              ly completed.  Applications can use this bind flag to selective‐
277              ly enable when completions are generated.  If  FI_SELECTIVE_COM‐
278              PLETION is specified, data transfer operations will not generate
279              CQ entries for successful completions  unless  FI_COMPLETION  is
280              set  as an operational flag for the given operation.  Operations
281              that fail asynchronously will still generate  completions,  even
282              if  a completion is not requested.  FI_SELECTIVE_COMPLETION must
283              be OR'ed with FI_TRANSMIT and/or FI_RECV flags.
284
285       When FI_SELECTIVE_COMPLETION is set, the user must determine when a re‐
286       quest  that  does  NOT have FI_COMPLETION set has completed indirectly,
287       usually based on the completion of a subsequent operation or  by  using
288       completion  counters.   Use of this flag may improve performance by al‐
289       lowing the provider to avoid writing a CQ completion  entry  for  every
290       operation.
291
292       See Notes section below for additional information on how this flag in‐
293       teracts with the FI_CONTEXT and FI_CONTEXT2 mode bits.
294
295       FI_TRANSMIT
296              Directs the completion of outbound data transfer requests to the
297              specified  completion  queue.   This includes send message, RMA,
298              and atomic operations.
299
300       An endpoint may optionally be bound to a completion counter.  Associat‐
301       ing  an endpoint with a counter is in addition to binding the EP with a
302       CQ.  When binding an endpoint to a counter, the following flags may  be
303       specified.
304
305       FI_READ
306              Increments  the  specified  counter whenever an RMA read, atomic
307              fetch, or atomic compare operation initiated from  the  endpoint
308              has completed successfully or in error.
309
310       FI_RECV
311              Increments  the specified counter whenever a message is received
312              over the endpoint.  Received messages include  both  tagged  and
313              normal message operations.
314
315       FI_REMOTE_READ
316              Increments  the  specified  counter whenever an RMA read, atomic
317              fetch, or atomic compare operation is initiated  from  a  remote
318              endpoint  that targets the given endpoint.  Use of this flag re‐
319              quires that the endpoint be created using FI_RMA_EVENT.
320
321       FI_REMOTE_WRITE
322              Increments the specified counter whenever an RMA write  or  base
323              atomic  operation  is initiated from a remote endpoint that tar‐
324              gets the given endpoint.  Use of this  flag  requires  that  the
325              endpoint be created using FI_RMA_EVENT.
326
327       FI_SEND
328              Increments  the  specified  counter  whenever a message transfer
329              initiated over the endpoint has completed successfully or in er‐
330              ror.  Sent messages include both tagged and normal message oper‐
331              ations.
332
333       FI_WRITE
334              Increments the specified counter whenever an RMA write  or  base
335              atomic  operation initiated from the endpoint has completed suc‐
336              cessfully or in error.
337
338       An endpoint may only be bound to a single CQ or  counter  for  a  given
339       type of operation.  For example, a EP may not bind to two counters both
340       using FI_WRITE.  Furthermore, providers may limit CQ and counter  bind‐
341       ings to endpoints of the same endpoint type (DGRAM, MSG, RDM, etc.).
342
343   fi_scalable_ep_bind
344       fi_scalable_ep_bind  is  used  to associate a scalable endpoint with an
345       address vector.  See section on SCALABLE ENDPOINTS.   A  scalable  end‐
346       point  has  a  single  transport level address and can support multiple
347       transmit and receive contexts.  The transmit and receive contexts share
348       the  transport-level  address.  Address vectors that are bound to scal‐
349       able endpoints are implicitly bound to any transmit or receive contexts
350       created using the scalable endpoint.
351
352   fi_enable
353       This  call transitions the endpoint into an enabled state.  An endpoint
354       must be enabled before it may be used to perform data  transfers.   En‐
355       abling  an  endpoint  typically results in hardware resources being as‐
356       signed to it.  Endpoints making use  of  completion  queues,  counters,
357       event queues, and/or address vectors must be bound to them before being
358       enabled.
359
360       Calling connect or accept on an endpoint will implicitly enable an end‐
361       point if it has not already been enabled.
362
363       fi_enable  may also be used to re-enable an endpoint that has been dis‐
364       abled as a result  of  experiencing  a  critical  error.   Applications
365       should  check the return value from fi_enable to see if a disabled end‐
366       point has successfully be re-enabled.
367
368   fi_cancel
369       fi_cancel attempts to cancel  an  outstanding  asynchronous  operation.
370       Canceling an operation causes the fabric provider to search for the op‐
371       eration and, if it is still pending, complete it as  having  been  can‐
372       celed.   An error queue entry will be available in the associated error
373       queue with error code FI_ECANCELED.  On the other hand, if  the  opera‐
374       tion completed before the call to fi_cancel, then the completion status
375       of that operation will be available in the associated completion queue.
376       No specific entry related to fi_cancel itself will be posted.
377
378       Cancel uses the context parameter associated with an operation to iden‐
379       tify the request to cancel.  Operations posted without a valid  context
380       parameter  --  either  no context parameter is specified or the context
381       value was ignored by the provider -- cannot be canceled.   If  multiple
382       outstanding  operations  match  the context parameter, only one will be
383       canceled.  In this case, the operation which is  canceled  is  provider
384       specific.   The  cancel  operation  is  asynchronous, but will complete
385       within a bounded period of time.
386
387   fi_ep_alias
388       This call creates an alias to the specified endpoint.  Conceptually, an
389       endpoint alias provides an alternate software path from the application
390       to the underlying provider hardware.  An alias EP differs from its par‐
391       ent  endpoint only by its default data transfer flags.  For example, an
392       alias EP may be configured to use a different completion mode.  By  de‐
393       fault,  an alias EP inherits the same data transfer flags as the parent
394       endpoint.  An application can use fi_control to modify the alias EP op‐
395       erational flags.
396
397       When  allocating  an  alias,  an  application  may configure either the
398       transmit or receive operational flags.  This avoids needing a  separate
399       call to fi_control to set those flags.  The flags passed to fi_ep_alias
400       must include FI_TRANSMIT or FI_RECV (not both) with  other  operational
401       flags  OR'ed in.  This will override the transmit or receive flags, re‐
402       spectively, for operations posted through the alias endpoint.  All  al‐
403       located  aliases  must  be closed for the underlying endpoint to be re‐
404       leased.
405
406   fi_control
407       The control operation is used to adjust the default behavior of an end‐
408       point.  It allows the underlying provider to redirect function calls to
409       implementations optimized to meet the desired application behavior.  As
410       a  result,  calls to fi_ep_control must be serialized against all other
411       calls to an endpoint.
412
413       The base operation of an endpoint is  selected  during  creation  using
414       struct  fi_info.   The  following control commands and arguments may be
415       assigned to an endpoint.
416
417       **FI_BACKLOG - int *value**
418              This option only applies to passive endpoints.  It  is  used  to
419              set the connection request backlog for listening endpoints.
420
421       **FI_GETOPSFLAG -- uint64_t *flags**
422              Used  to retrieve the current value of flags associated with the
423              data transfer operations initiated on the endpoint.  The control
424              argument must include FI_TRANSMIT or FI_RECV (not both) flags to
425              indicate the type of data transfer flags to  be  returned.   See
426              below for a list of control flags.
427
428       FI_GETWAIT -- void **
429              This command allows the user to retrieve the file descriptor as‐
430              sociated with a socket endpoint.  The fi_control  arg  parameter
431              should  be  an  address where a pointer to the returned file de‐
432              scriptor will be written.  See fi_eq.3 for addition details  us‐
433              ing fi_control with FI_GETWAIT.  The file descriptor may be used
434              for notification that the endpoint is ready to send  or  receive
435              data.
436
437       **FI_SETOPSFLAG -- uint64_t *flags**
438              Used to change the data transfer operation flags associated with
439              an endpoint.  The control argument must include  FI_TRANSMIT  or
440              FI_RECV  (not  both)  to indicate the type of data transfer that
441              the flags should apply to, with other flags OR'ed in.  The given
442              flags will override the previous transmit and receive attributes
443              that were set when the  endpoint  was  created.   Valid  control
444              flags are defined below.
445
446   fi_getopt / fi_setopt
447       Endpoint  protocol  operations  may be retrieved using fi_getopt or set
448       using fi_setopt.  Applications specify the level that a desired  option
449       exists, identify the option, and provide input/output buffers to get or
450       set the option.  fi_setopt provides an  application  a  way  to  adjust
451       low-level protocol and implementation specific details of an endpoint.
452
453       The  following  option  levels  and option names and parameters are de‐
454       fined.
455
456       FI_OPT_ENDPOINT · .RS 2
457
458       FI_OPT_BUFFERED_LIMIT - size_t
459              Defines the maximum size of a buffered message that will be  re‐
460              ported  to  users  as  part  of  a  receive  completion when the
461              FI_BUFFERED_RECV mode is enabled on an endpoint.
462
463       fi_getopt() will return the  currently  configured  threshold,  or  the
464       provider's  default threshold if one has not be set by the application.
465       fi_setopt() allows an application to configure the threshold.   If  the
466       provider  cannot  support  the  requested  threshold,  it will fail the
467       fi_setopt()  call  with  FI_EMSGSIZE.   Calling  fi_setopt()  with  the
468       threshold  set  to  SIZE_MAX will set the threshold to the maximum sup‐
469       ported by the provider.  fi_getopt() can then be used to  retrieve  the
470       set size.
471
472       In  most  cases, the sending and receiving endpoints must be configured
473       to use the same threshold value, and the threshold must be set prior to
474       enabling the endpoint.  · .RS 2
475
476       FI_OPT_BUFFERED_MIN - size_t
477              Defines  the minimum size of a buffered message that will be re‐
478              ported.  Applications would set this to a size that's big enough
479              to decide whether to discard or claim a buffered receive or when
480              to claim a buffered receive on getting a buffered  receive  com‐
481              pletion.  The value is typically used by a provider when sending
482              a rendezvous protocol request  where  it  would  send  at  least
483              FI_OPT_BUFFERED_MIN  bytes of application data along with it.  A
484              smaller sized rendezvous protocol  message  usually  results  in
485              better latency for the overall transfer of a large message.
486       · .RS 2
487
488       FI_OPT_CM_DATA_SIZE - size_t
489              Defines  the size of available space in CM messages for user-de‐
490              fined data.  This value limits the amount of data that  applica‐
491              tions  can exchange between peer endpoints using the fi_connect,
492              fi_accept, and fi_reject operations.  The size returned  is  de‐
493              pendent  upon the properties of the endpoint, except in the case
494              of passive endpoints, in which the  size  reflects  the  maximum
495              size of the data that may be present as part of a connection re‐
496              quest event.  This option is read only.
497       · .RS 2
498
499       FI_OPT_MIN_MULTI_RECV - size_t
500              Defines the minimum receive buffer space available when the  re‐
501              ceive  buffer  is  released by the provider (see FI_MULTI_RECV).
502              Modifying this value is only guaranteed to set the minimum  buf‐
503              fer  space  needed  on  receives posted after the value has been
504              changed.  It is recommended that applications that want to over‐
505              ride the default MIN_MULTI_RECV value set this option before en‐
506              abling the corresponding endpoint.
507
508   fi_tc_dscp_set
509       This call converts a DSCP defined value into a libfabric traffic  class
510       value.   It should be used when assigning a DSCP value when setting the
511       tclass field in either domain or endpoint attributes
512
513   fi_tc_dscp_get
514       This call returns the DSCP value associated with the tclass  field  for
515       the domain or endpoint attributes.
516
517   fi_rx_size_left (DEPRECATED)
518       This  function has been deprecated and will be removed in a future ver‐
519       sion of the library.  It may not be supported by all providers.
520
521       The fi_rx_size_left call returns a lower bound on the number of receive
522       operations that may be posted to the given endpoint without that opera‐
523       tion returning -FI_EAGAIN.  Depending on the specific  details  of  the
524       subsequently  posted  receive  operations (e.g., number of iov entries,
525       which receive function is called, etc.), it may  be  possible  to  post
526       more receive operations than originally indicated by fi_rx_size_left.
527
528   fi_tx_size_left (DEPRECATED)
529       This  function has been deprecated and will be removed in a future ver‐
530       sion of the library.  It may not be supported by all providers.
531
532       The fi_tx_size_left call returns a lower bound on the number of  trans‐
533       mit  operations  that  may be posted to the given endpoint without that
534       operation returning -FI_EAGAIN.  Depending on the specific  details  of
535       the  subsequently  posted  transmit operations (e.g., number of iov en‐
536       tries, which transmit function is called, etc.), it may be possible  to
537       post   more   transmit   operations   than   originally   indicated  by
538       fi_tx_size_left.
539

ENDPOINT ATTRIBUTES

541       The fi_ep_attr structure defines the set of attributes associated  with
542       an  endpoint.   Endpoint  attributes  may  be further refined using the
543       transmit and receive context attributes as shown below.
544
545              struct fi_ep_attr {
546                  enum fi_ep_type type;
547                  uint32_t        protocol;
548                  uint32_t        protocol_version;
549                  size_t          max_msg_size;
550                  size_t          msg_prefix_size;
551                  size_t          max_order_raw_size;
552                  size_t          max_order_war_size;
553                  size_t          max_order_waw_size;
554                  uint64_t        mem_tag_format;
555                  size_t          tx_ctx_cnt;
556                  size_t          rx_ctx_cnt;
557                  size_t          auth_key_size;
558                  uint8_t         *auth_key;
559              };
560
561   type - Endpoint Type
562       If specified, indicates the type of fabric interface communication  de‐
563       sired.  Supported types are:
564
565       FI_EP_DGRAM
566              Supports  a  connectionless,  unreliable datagram communication.
567              Message boundaries are maintained, but the maximum message  size
568              may  be  limited to the fabric MTU.  Flow control is not guaran‐
569              teed.
570
571       FI_EP_MSG
572              Provides a reliable, connection-oriented data  transfer  service
573              with flow control that maintains message boundaries.
574
575       FI_EP_RDM
576              Reliable datagram message.  Provides a reliable, unconnected da‐
577              ta transfer service with flow  control  that  maintains  message
578              boundaries.
579
580       FI_EP_SOCK_DGRAM
581              A  connectionless,  unreliable  datagram endpoint with UDP sock‐
582              et-like semantics.  FI_EP_SOCK_DGRAM is most useful for applica‐
583              tions  designed  around  using UDP sockets.  See the SOCKET END‐
584              POINT section for additional details and restrictions that apply
585              to datagram socket endpoints.
586
587       FI_EP_SOCK_STREAM
588              Data  streaming  endpoint  with TCP socket-like semantics.  Pro‐
589              vides a reliable, connection-oriented data transfer service that
590              does not maintain message boundaries.  FI_EP_SOCK_STREAM is most
591              useful for applications designed around using TCP sockets.   See
592              the  SOCKET ENDPOINT section for additional details and restric‐
593              tions that apply to stream endpoints.
594
595       FI_EP_UNSPEC
596              The type of endpoint is not specified.  This is usually provided
597              as  input, with other attributes of the endpoint or the provider
598              selecting the type.
599
600   Protocol
601       Specifies the low-level end to end protocol employed by  the  provider.
602       A  matching  protocol must be used by communicating endpoints to ensure
603       interoperability.  The following protocol values are defined.  Provider
604       specific  protocols are also allowed.  Provider specific protocols will
605       be indicated by having the upper bit of the protocol value set to one.
606
607       FI_PROTO_GNI
608              Protocol runs over Cray GNI low-level interface.
609
610       FI_PROTO_IB_RDM
611              Reliable-datagram protocol  implemented  over  InfiniBand  reli‐
612              able-connected queue pairs.
613
614       FI_PROTO_IB_UD
615              The  protocol  runs  over  Infiniband  unreliable datagram queue
616              pairs.
617
618       FI_PROTO_IWARP
619              The protocol runs over the  Internet  wide  area  RDMA  protocol
620              transport.
621
622       FI_PROTO_IWARP_RDM
623              Reliable-datagram  protocol implemented over iWarp reliable-con‐
624              nected queue pairs.
625
626       FI_PROTO_NETWORKDIRECT
627              Protocol runs over Microsoft NetworkDirect service provider  in‐
628              terface.   This  adds  reliable-datagram semantics over the Net‐
629              workDirect connection- oriented endpoint semantics.
630
631       FI_PROTO_PSMX
632              The protocol is based on an Intel proprietary protocol known  as
633              PSM,  performance scaled messaging.  PSMX is an extended version
634              of the PSM protocol to support the libfabric interfaces.
635
636       FI_PROTO_PSMX2
637              The protocol is based on an Intel proprietary protocol known  as
638              PSM2,  performance  scaled messaging version 2.  PSMX2 is an ex‐
639              tended version of the PSM2 protocol to support the libfabric in‐
640              terfaces.
641
642       FI_PROTO_RDMA_CM_IB_RC
643              The  protocol  runs  over  Infiniband  reliable-connected  queue
644              pairs, using the RDMA CM protocol for connection establishment.
645
646       FI_PROTO_RXD
647              Reliable-datagram protocol implemented over datagram  endpoints.
648              RXD  is a libfabric utility component that adds RDM endpoint se‐
649              mantics over DGRAM endpoint semantics.
650
651       FI_PROTO_RXM
652              Reliable-datagram protocol implemented over  message  endpoints.
653              RXM  is a libfabric utility component that adds RDM endpoint se‐
654              mantics over MSG endpoint semantics.
655
656       FI_PROTO_SOCK_TCP
657              The protocol is layered over TCP packets.
658
659       FI_PROTO_UDP
660              The protocol sends and receives UDP datagrams.  For example,  an
661              endpoint  using  FI_PROTO_UDP will be able to communicate with a
662              remote peer that is using Berkeley SOCK_DGRAM sockets using  IP‐
663              PROTO_UDP.
664
665       FI_PROTO_UNSPEC
666              The  protocol is not specified.  This is usually provided as in‐
667              put, with other attributes of the socket or the provider select‐
668              ing the actual protocol.
669
670   protocol_version - Protocol Version
671       Identifies  which  version of the protocol is employed by the provider.
672       The protocol version allows providers to extend an  existing  protocol,
673       by adding support for additional features or functionality for example,
674       in a backward compatible manner.  Providers that support different ver‐
675       sions  of  the  same protocol should inter-operate, but only when using
676       the capabilities defined for the lesser version.
677
678   max_msg_size - Max Message Size
679       Defines the maximum size for an application data transfer as  a  single
680       operation.
681
682   msg_prefix_size - Message Prefix Size
683       Specifies  the  size of any required message prefix buffer space.  This
684       field will be 0 unless the FI_MSG_PREFIX mode is enabled.  If  msg_pre‐
685       fix_size is > 0 the specified value will be a multiple of 8-bytes.
686
687   Max RMA Ordered Size
688       The maximum ordered size specifies the delivery order of transport data
689       into target memory for RMA and atomic  operations.   Data  ordering  is
690       separate,  but dependent on message ordering (defined below).  Data or‐
691       dering is unspecified where message order is not defined.
692
693       Data ordering refers to the access of target memory by subsequent oper‐
694       ations.  When back to back RMA read or write operations access the same
695       registered memory location, data ordering indicates whether the  second
696       operation  reads  or writes the target memory after the first operation
697       has completed.  Because RMA ordering applies  between  two  operations,
698       and not within a single data transfer, ordering is defined per byte-ad‐
699       dressable memory location.  I.e.  ordering specifies whether location X
700       is accessed by the second operation after the first operation.  Nothing
701       is implied about the completion of the first operation before the  sec‐
702       ond operation is initiated.
703
704       In  order  to  support  large data transfers being broken into multiple
705       packets and sent using multiple paths through the fabric, data ordering
706       may  be  limited  to  transfers  of a specific size or less.  Providers
707       specify when data ordering is maintained through the following  values.
708       Note that even if data ordering is not maintained, message ordering may
709       be.
710
711       max_order_raw_size
712              Read after write size.  If set, an RMA or atomic read  operation
713              issued after an RMA or atomic write operation, both of which are
714              smaller than the size, will be ordered.  Where the target memory
715              locations overlap, the RMA or atomic read operation will see the
716              results of the previous RMA or atomic write.
717
718       max_order_war_size
719              Write after read size.  If set, an RMA or atomic write operation
720              issued  after an RMA or atomic read operation, both of which are
721              smaller than the size, will be ordered.  The RMA or atomic  read
722              operation  will see the initial value of the target memory loca‐
723              tion before a subsequent RMA or atomic write updates the value.
724
725       max_order_waw_size
726              Write after write size.  If set, an RMA or atomic  write  opera‐
727              tion  issued  after  an  RMA  or atomic write operation, both of
728              which are smaller than the size, will be  ordered.   The  target
729              memory  location  will  reflect the results of the second RMA or
730              atomic write.
731
732       An order size value of 0 indicates that ordering is not guaranteed.   A
733       value of -1 guarantees ordering for any data size.
734
735   mem_tag_format - Memory Tag Format
736       The  memory  tag  format  is  a  bit array used to convey the number of
737       tagged bits supported by a provider.  Additionally, it may be  used  to
738       divide  the bit array into separate fields.  The mem_tag_format option‐
739       ally begins with a series of bits set to 0, to signify bits  which  are
740       ignored by the provider.  Following the initial prefix of ignored bits,
741       the array will consist of alternating groups of bits set to all 1's  or
742       all 0's.  Each group of bits corresponds to a tagged field.  The impli‐
743       cation of defining a tagged field is that when a mask is applied to the
744       tagged  bit  array, all bits belonging to a single field will either be
745       set to 1 or 0, collectively.
746
747       For example, a mem_tag_format of 0x30FF indicates support for 14 tagged
748       bits, separated into 3 fields.  The first field consists of 2-bits, the
749       second field 4-bits, and the final field 8-bits.  Valid masks for  such
750       a tagged field would be a bitwise OR'ing of zero or more of the follow‐
751       ing values: 0x3000, 0x0F00, and 0x00FF.  The provider may not  validate
752       the mask provided by the application for performance reasons.
753
754       By  identifying fields within a tag, a provider may be able to optimize
755       their search routines.  An application which requests tag  fields  must
756       provide  tag  masks  that  either  set all mask bits corresponding to a
757       field to all 0 or all 1.  When negotiating tag fields,  an  application
758       can  request  a  specific number of fields of a given size.  A provider
759       must return a tag format that supports the requested number of  fields,
760       with each field being at least the size requested, or fail the request.
761       A provider may increase the size of the fields.  When reporting comple‐
762       tions (see FI_CQ_FORMAT_TAGGED), it is not guaranteed that the provider
763       would clear out any unsupported tag bits in the tag field of  the  com‐
764       pletion entry.
765
766       It is recommended that field sizes be ordered from smallest to largest.
767       A generic, unstructured tag and mask can be achieved  by  requesting  a
768       bit array consisting of alternating 1's and 0's.
769
770   tx_ctx_cnt - Transmit Context Count
771       Number  of  transmit  contexts  to associate with the endpoint.  If not
772       specified (0), 1 context will be assigned if the endpoint supports out‐
773       bound  transfers.   Transmit  contexts  are independent transmit queues
774       that may be separately configured.  Each transmit context may be  bound
775       to  a  separate CQ, and no ordering is defined between contexts.  Addi‐
776       tionally, no synchronization is needed when accessing contexts in  par‐
777       allel.
778
779       If  the  count is set to the value FI_SHARED_CONTEXT, the endpoint will
780       be configured to use a shared transmit context,  if  supported  by  the
781       provider.   Providers that do not support shared transmit contexts will
782       fail the request.
783
784       See the scalable endpoint and shared contexts sections  for  additional
785       details.
786
787   rx_ctx_cnt - Receive Context Count
788       Number  of  receive  contexts  to  associate with the endpoint.  If not
789       specified, 1 context will be assigned if the endpoint supports  inbound
790       transfers.  Receive contexts are independent processing queues that may
791       be separately configured.  Each receive context may be bound to a sepa‐
792       rate CQ, and no ordering is defined between contexts.  Additionally, no
793       synchronization is needed when accessing contexts in parallel.
794
795       If the count is set to the value FI_SHARED_CONTEXT, the  endpoint  will
796       be  configured  to  use  a  shared receive context, if supported by the
797       provider.  Providers that do not support shared receive  contexts  will
798       fail the request.
799
800       See  the  scalable endpoint and shared contexts sections for additional
801       details.
802
803   auth_key_size - Authorization Key Length
804       The length of the authorization key in bytes.  This field will be 0  if
805       authorization  keys  are  not available or used.  This field is ignored
806       unless the fabric is opened with API version 1.5 or greater.
807
808   auth_key - Authorization Key
809       If supported by the fabric, an authorization key (a.k.a.  job  key)  to
810       associate  with  the  endpoint.   An authorization key is used to limit
811       communication between endpoints.  Only peer  endpoints  that  are  pro‐
812       grammed  to use the same authorization key may communicate.  Authoriza‐
813       tion keys are often used to implement job keys, to ensure that process‐
814       es  running  in  different jobs do not accidentally cross traffic.  The
815       domain authorization key will be used if auth_key_size  is  set  to  0.
816       This  field is ignored unless the fabric is opened with API version 1.5
817       or greater.
818

TRANSMIT CONTEXT ATTRIBUTES

820       Attributes specific to the transmit capabilities  of  an  endpoint  are
821       specified using struct fi_tx_attr.
822
823              struct fi_tx_attr {
824                  uint64_t  caps;
825                  uint64_t  mode;
826                  uint64_t  op_flags;
827                  uint64_t  msg_order;
828                  uint64_t  comp_order;
829                  size_t    inject_size;
830                  size_t    size;
831                  size_t    iov_limit;
832                  size_t    rma_iov_limit;
833                  uint32_t  tclass;
834              };
835
836   caps - Capabilities
837       The  requested capabilities of the context.  The capabilities must be a
838       subset of those requested of the associated endpoint.  See the CAPABIL‐
839       ITIES  section  of  fi_getinfo(3)  for capability details.  If the caps
840       field is 0 on input to fi_getinfo(3), the  applicable  capability  bits
841       from the fi_info structure will be used.
842
843       The  following  capabilities  apply to the transmit attributes: FI_MSG,
844       FI_RMA, FI_TAGGED,  FI_ATOMIC,  FI_READ,  FI_WRITE,  FI_SEND,  FI_HMEM,
845       FI_TRIGGER, FI_FENCE, FI_MULTICAST, FI_RMA_PMEM, and FI_NAMED_RX_CTX.
846
847       Many  applications will be able to ignore this field and rely solely on
848       the fi_info::caps field.  Use of this field provides fine grained  con‐
849       trol over the transmit capabilities associated with an endpoint.  It is
850       useful when handling scalable endpoints, with  multiple  transmit  con‐
851       texts,  for example, and allows configuring a specific transmit context
852       with fewer capabilities than that supported by the  endpoint  or  other
853       transmit contexts.
854
855   mode
856       The operational mode bits of the context.  The mode bits will be a sub‐
857       set of those associated with the endpoint.  See  the  MODE  section  of
858       fi_getinfo(3)  for details.  A mode value of 0 will be ignored on input
859       to fi_getinfo(3), with the mode value of the fi_info structure used in‐
860       stead.   On  return  from  fi_getinfo(3),  the mode will be set only to
861       those constraints specific to transmit operations.
862
863   op_flags - Default transmit operation flags
864       Flags that control the operation of operations  submitted  against  the
865       context.  Applicable flags are listed in the Operation Flags section.
866
867   msg_order - Message Ordering
868       Message  ordering  refers to the order in which transport layer headers
869       (as viewed by the application) are identified and  processed.   Relaxed
870       message order enables data transfers to be sent and received out of or‐
871       der, which may improve performance by utilizing multiple paths  through
872       the  fabric from the initiating endpoint to a target endpoint.  Message
873       order applies only between a single  source  and  destination  endpoint
874       pair.  Ordering between different target endpoints is not defined.
875
876       Message order is determined using a set of ordering bits.  Each set bit
877       indicates that ordering is maintained between  data  transfers  of  the
878       specified type.  Message order is defined for [read | write | send] op‐
879       erations submitted by an application after [read | write | send] opera‐
880       tions.
881
882       Message  ordering only applies to the end to end transmission of trans‐
883       port headers.  Message ordering is necessary, but does  not  guarantee,
884       the  order  in  which message data is sent or received by the transport
885       layer.  Message ordering requires matching ordering  semantics  on  the
886       receiving  side of a data transfer operation in order to guarantee that
887       ordering is met.
888
889       FI_ORDER_ATOMIC_RAR
890              Atomic read after read.  If set,  atomic  fetch  operations  are
891              transmitted  in  the  order  submitted  relative to other atomic
892              fetch operations.  If not set, atomic fetches may be transmitted
893              out of order from their submission.
894
895       FI_ORDER_ATOMIC_RAW
896              Atomic  read  after  write.  If set, atomic fetch operations are
897              transmitted in the order submitted relative to atomic update op‐
898              erations.   If  not set, atomic fetches may be transmitted ahead
899              of atomic updates.
900
901       FI_ORDER_ATOMIC_WAR
902              RMA write after read.  If  set,  atomic  update  operations  are
903              transmitted  in the order submitted relative to atomic fetch op‐
904              erations.  If not set, atomic updates may be  transmitted  ahead
905              of atomic fetches.
906
907       FI_ORDER_ATOMIC_WAW
908              RMA  write  after  write.   If set, atomic update operations are
909              transmitted in the order submitted relative to other atomic  up‐
910              date  operations.   If not atomic updates may be transmitted out
911              of order from their submission.
912
913       FI_ORDER_NONE
914              No ordering is specified.  This value may be used  as  input  in
915              order  to  obtain  the  default  message  order supported by the
916              provider.  FI_ORDER_NONE is an alias for the value 0.
917
918       FI_ORDER_RAR
919              Read after read.  If set, RMA and  atomic  read  operations  are
920              transmitted  in  the  order  submitted relative to other RMA and
921              atomic read operations.  If not set, RMA and atomic reads may be
922              transmitted out of order from their submission.
923
924       FI_ORDER_RAS
925              Read  after  send.   If  set, RMA and atomic read operations are
926              transmitted in the order submitted relative to message send  op‐
927              erations,  including  tagged  sends.  If not set, RMA and atomic
928              reads may be transmitted ahead of sends.
929
930       FI_ORDER_RAW
931              Read after write.  If set, RMA and atomic  read  operations  are
932              transmitted  in  the  order submitted relative to RMA and atomic
933              write operations.  If not set,  RMA  and  atomic  reads  may  be
934              transmitted ahead of RMA and atomic writes.
935
936       FI_ORDER_RMA_RAR
937              RMA  read after read.  If set, RMA read operations are transmit‐
938              ted in the order submitted relative to  other  RMA  read  opera‐
939              tions.   If  not  set, RMA reads may be transmitted out of order
940              from their submission.
941
942       FI_ORDER_RMA_RAW
943              RMA read after write.  If set, RMA read operations are transmit‐
944              ted in the order submitted relative to RMA write operations.  If
945              not set, RMA reads may be transmitted ahead of RMA writes.
946
947       FI_ORDER_RMA_WAR
948              RMA write after read.  If set, RMA write operations  are  trans‐
949              mitted  in  the order submitted relative to RMA read operations.
950              If not set, RMA writes may be transmitted ahead of RMA reads.
951
952       FI_ORDER_RMA_WAW
953              RMA write after write.  If set, RMA write operations are  trans‐
954              mitted in the order submitted relative to other RMA write opera‐
955              tions.  If not set, RMA writes may be transmitted out  of  order
956              from their submission.
957
958       FI_ORDER_SAR
959              Send  after  read.   If  set, message send operations, including
960              tagged sends, are transmitted in order submitted relative to RMA
961              and  atomic  read  operations.  If not set, message sends may be
962              transmitted ahead of RMA and atomic reads.
963
964       FI_ORDER_SAS
965              Send after send.  If set,  message  send  operations,  including
966              tagged sends, are transmitted in the order submitted relative to
967              other message send.  If not set, message sends may be  transmit‐
968              ted out of order from their submission.
969
970       FI_ORDER_SAW
971              Send  after  write.   If set, message send operations, including
972              tagged sends, are transmitted in order submitted relative to RMA
973              and  atomic  write operations.  If not set, message sends may be
974              transmitted ahead of RMA and atomic writes.
975
976       FI_ORDER_WAR
977              Write after read.  If set, RMA and atomic write  operations  are
978              transmitted  in  the  order submitted relative to RMA and atomic
979              read operations.  If not set,  RMA  and  atomic  writes  may  be
980              transmitted ahead of RMA and atomic reads.
981
982       FI_ORDER_WAS
983              Write  after  send.  If set, RMA and atomic write operations are
984              transmitted in the order submitted relative to message send  op‐
985              erations,  including  tagged  sends.  If not set, RMA and atomic
986              writes may be transmitted ahead of sends.
987
988       FI_ORDER_WAW
989              Write after write.  If set, RMA and atomic write operations  are
990              transmitted  in  the  order  submitted relative to other RMA and
991              atomic write operations.  If not set, RMA and atomic writes  may
992              be transmitted out of order from their submission.
993
994   comp_order - Completion Ordering
995       Completion ordering refers to the order in which completed requests are
996       written into the completion queue.  Completion ordering is  similar  to
997       message order.  Relaxed completion order may enable faster reporting of
998       completed transfers, allow acknowledgments to be  sent  over  different
999       fabric  paths,  and  support more sophisticated retry mechanisms.  This
1000       can result in lower-latency completions, particularly when using uncon‐
1001       nected   endpoints.    Strict  completion  ordering  may  require  that
1002       providers queue completed operations or limit available optimizations.
1003
1004       For transmit requests, completion ordering depends on the endpoint com‐
1005       munication type.  For unreliable communication, completion ordering ap‐
1006       plies to all data transfer requests submitted to an endpoint.  For  re‐
1007       liable communication, completion ordering only applies to requests that
1008       target a single destination endpoint.  Completion ordering of  requests
1009       that  target  different  endpoints over a reliable transport is not de‐
1010       fined.
1011
1012       Applications should specify the completion ordering that  they  support
1013       or require.  Providers should return the completion order that they ac‐
1014       tually provide, with the  constraint  that  the  returned  ordering  is
1015       stricter  than that specified by the application.  Supported completion
1016       order values are:
1017
1018       FI_ORDER_NONE
1019              No ordering is defined for completed operations.  Requests  sub‐
1020              mitted to the transmit context may complete in any order.
1021
1022       FI_ORDER_STRICT
1023              Requests  complete  in  the order in which they are submitted to
1024              the transmit context.
1025
1026   inject_size
1027       The requested inject operation size (see the FI_INJECT flag)  that  the
1028       context  will support.  This is the maximum size data transfer that can
1029       be associated with an inject operation (such as fi_inject)  or  may  be
1030       used with the FI_INJECT data transfer flag.
1031
1032   size
1033       The  size  of the context.  The size is specified as the minimum number
1034       of transmit operations that may be posted to the endpoint  without  the
1035       operation returning -FI_EAGAIN.
1036
1037   iov_limit
1038       This is the maximum number of IO vectors (scatter-gather elements) that
1039       a single posted operation may reference.
1040
1041   rma_iov_limit
1042       This is the maximum number of RMA IO vectors (scatter-gather  elements)
1043       that  an RMA or atomic operation may reference.  The rma_iov_limit cor‐
1044       responds to the rma_iov_count values in RMA and atomic operations.  See
1045       struct fi_msg_rma and struct fi_msg_atomic in fi_rma.3 and fi_atomic.3,
1046       for additional details.  This limit applies to both the number  of  RMA
1047       IO  vectors that may be specified when initiating an operation from the
1048       local endpoint, as well as the maximum number of IO vectors that may be
1049       carried in a single request from a remote endpoint.
1050
1051   Traffic Class (tclass)
1052       Traffic classes can be a differentiated services code point (DSCP) val‐
1053       ue, one of the following defined labels, or a provider-specific defini‐
1054       tion.  If tclass is unset or set to FI_TC_UNSPEC, the endpoint will use
1055       the default traffic class associated with the domain.
1056
1057       FI_TC_BEST_EFFORT
1058              This is the default in the absence of any other local or  fabric
1059              configuration.   This  class carries the traffic for a number of
1060              applications executing concurrently over the same network infra‐
1061              structure.   Even  though it is shared, network capacity and re‐
1062              source allocation are distributed  fairly  across  the  applica‐
1063              tions.
1064
1065       FI_TC_BULK_DATA
1066              This  class is intended for large data transfers associated with
1067              I/O and is present to separate sustained I/O transfers from oth‐
1068              er application inter-process communications.
1069
1070       FI_TC_DEDICATED_ACCESS
1071              This  class operates at the highest priority, except the manage‐
1072              ment class.  It carries a high bandwidth allocation, minimum la‐
1073              tency targets, and the highest scheduling and arbitration prior‐
1074              ity.
1075
1076       FI_TC_LOW_LATENCY
1077              This class supports low latency, low jitter data patterns  typi‐
1078              cally  caused  by transactional data exchanges, barrier synchro‐
1079              nizations, and collective operations that are typical of HPC ap‐
1080              plications.   This class often requires maximum tolerable laten‐
1081              cies that data transfers must achieve for correct or performance
1082              operations.   Fulfillment  of  such  requests in this class will
1083              typically require accompanying bandwidth and message size  limi‐
1084              tations so as not to consume excessive bandwidth at high priori‐
1085              ty.
1086
1087       FI_TC_NETWORK_CTRL
1088              This class is intended for traffic directly  related  to  fabric
1089              (network) management, which is critical to the correct operation
1090              of the network.  Its use is typically restricted  to  privileged
1091              network management applications.
1092
1093       FI_TC_SCAVENGER
1094              This  class  is  used for data that is desired but does not have
1095              strict delivery requirements, such as in-band network or  appli‐
1096              cation  level monitoring data.  Use of this class indicates that
1097              the traffic is considered lower priority and should  not  inter‐
1098              fere with higher priority workflows.
1099
1100       fi_tc_dscp_set / fi_tc_dscp_get
1101              DSCP  values  are  supported via the DSCP get and set functions.
1102              The definitions for DSCP values are outside the scope of libfab‐
1103              ric.  See the fi_tc_dscp_set and fi_tc_dscp_get function defini‐
1104              tions for details on their use.
1105

RECEIVE CONTEXT ATTRIBUTES

1107       Attributes specific to the receive  capabilities  of  an  endpoint  are
1108       specified using struct fi_rx_attr.
1109
1110              struct fi_rx_attr {
1111                  uint64_t  caps;
1112                  uint64_t  mode;
1113                  uint64_t  op_flags;
1114                  uint64_t  msg_order;
1115                  uint64_t  comp_order;
1116                  size_t    total_buffered_recv;
1117                  size_t    size;
1118                  size_t    iov_limit;
1119              };
1120
1121   caps - Capabilities
1122       The  requested capabilities of the context.  The capabilities must be a
1123       subset of those requested of the associated endpoint.  See the CAPABIL‐
1124       ITIES  section  if  fi_getinfo(3)  for capability details.  If the caps
1125       field is 0 on input to fi_getinfo(3), the  applicable  capability  bits
1126       from the fi_info structure will be used.
1127
1128       The  following  capabilities  apply  to the receive attributes: FI_MSG,
1129       FI_RMA, FI_TAGGED, FI_ATOMIC, FI_REMOTE_READ, FI_REMOTE_WRITE, FI_RECV,
1130       FI_HMEM,  FI_TRIGGER,  FI_RMA_PMEM,  FI_DIRECTED_RECV, FI_VARIABLE_MSG,
1131       FI_MULTI_RECV, FI_SOURCE, FI_RMA_EVENT, and FI_SOURCE_ERR.
1132
1133       Many applications will be able to ignore this field and rely solely  on
1134       the  fi_info::caps field.  Use of this field provides fine grained con‐
1135       trol over the receive capabilities associated with an endpoint.  It  is
1136       useful  when  handling  scalable  endpoints, with multiple receive con‐
1137       texts, for example, and allows configuring a specific  receive  context
1138       with  fewer  capabilities  than that supported by the endpoint or other
1139       receive contexts.
1140
1141   mode
1142       The operational mode bits of the context.  The mode bits will be a sub‐
1143       set  of  those  associated  with the endpoint.  See the MODE section of
1144       fi_getinfo(3) for details.  A mode value of 0 will be ignored on  input
1145       to fi_getinfo(3), with the mode value of the fi_info structure used in‐
1146       stead.  On return from fi_getinfo(3), the mode  will  be  set  only  to
1147       those constraints specific to receive operations.
1148
1149   op_flags - Default receive operation flags
1150       Flags  that  control  the operation of operations submitted against the
1151       context.  Applicable flags are listed in the Operation Flags section.
1152
1153   msg_order - Message Ordering
1154       For a description of message ordering, see the msg_order field  in  the
1155       Transmit  Context  Attribute section.  Receive context message ordering
1156       defines the order in which received transport message headers are  pro‐
1157       cessed  when  received  by an endpoint.  When ordering is set, it indi‐
1158       cates that message headers will be processed in order, based on how the
1159       transmit  side has identified the messages.  Typically, this means that
1160       messages will be handled in order based on  a  message  level  sequence
1161       number.
1162
1163       The  following  ordering  flags, as defined for transmit ordering, also
1164       apply to the processing of received operations:  FI_ORDER_NONE,  FI_OR‐
1165       DER_RAR, FI_ORDER_RAW, FI_ORDER_RAS, FI_ORDER_WAR, FI_ORDER_WAW, FI_OR‐
1166       DER_WAS, FI_ORDER_SAR,  FI_ORDER_SAW,  FI_ORDER_SAS,  FI_ORDER_RMA_RAR,
1167       FI_ORDER_RMA_RAW,  FI_ORDER_RMA_WAR,  FI_ORDER_RMA_WAW,  FI_ORDER_ATOM‐
1168       IC_RAR, FI_ORDER_ATOMIC_RAW,  FI_ORDER_ATOMIC_WAR,  and  FI_ORDER_ATOM‐
1169       IC_WAW.
1170
1171   comp_order - Completion Ordering
1172       For  a  description of completion ordering, see the comp_order field in
1173       the Transmit Context Attribute section.
1174
1175       FI_ORDER_DATA
1176              When set, this bit indicates that received data is written  into
1177              memory  in  order.   Data ordering applies to memory accessed as
1178              part of a single operation and between operations if message or‐
1179              dering is guaranteed.
1180
1181       FI_ORDER_NONE
1182              No ordering is defined for completed operations.  Receive opera‐
1183              tions may complete in any order, regardless of their  submission
1184              order.
1185
1186       FI_ORDER_STRICT
1187              Receive  operations complete in the order in which they are pro‐
1188              cessed by the receive context, based on the receive side msg_or‐
1189              der attribute.
1190
1191   total_buffered_recv
1192       This  field is supported for backwards compatibility purposes.  It is a
1193       hint to the provider of the total available space that may be needed to
1194       buffer  messages  that  are received for which there is no matching re‐
1195       ceive operation.  The provider may adjust or ignore  this  value.   The
1196       allocation  of  internal  network  buffering  among received message is
1197       provider specific.  For instance, a provider may limit the size of mes‐
1198       sages  which  can be buffered or the amount of buffering allocated to a
1199       single message.
1200
1201       If receive side buffering is disabled (total_buffered_recv = 0)  and  a
1202       message  is  received by an endpoint, then the behavior is dependent on
1203       whether resource management has been enabled (FI_RM_ENABLED has be  set
1204       or  not).   See the Resource Management section of fi_domain.3 for fur‐
1205       ther clarification.  It is recommended  that  applications  enable  re‐
1206       source  management  if  they  anticipate receiving unexpected messages,
1207       rather than modifying this value.
1208
1209   size
1210       The size of the context.  The size is specified as the  minimum  number
1211       of  receive  operations  that may be posted to the endpoint without the
1212       operation returning -FI_EAGAIN.
1213
1214   iov_limit
1215       This is the maximum number of IO vectors (scatter-gather elements) that
1216       a single posted operating may reference.
1217

SCALABLE ENDPOINTS

1219       A  scalable  endpoint  is a communication portal that supports multiple
1220       transmit and receive contexts.  Scalable endpoints are loosely  modeled
1221       after  the  networking  concept  of transmit/receive side scaling, also
1222       known as multi-queue.  Support for scalable endpoints is domain specif‐
1223       ic.   Scalable  endpoints may improve the performance of multi-threaded
1224       and parallel applications, by allowing threads  to  access  independent
1225       transmit  and  receive queues.  A scalable endpoint has a single trans‐
1226       port level address, which can reduce the memory requirements needed  to
1227       store  remote  addressing data, versus using standard endpoints.  Scal‐
1228       able endpoints cannot be used directly  for  communication  operations,
1229       and  require  the application to explicitly create transmit and receive
1230       contexts as described below.
1231
1232   fi_tx_context
1233       Transmit contexts are independent transmit queues.  Ordering  and  syn‐
1234       chronization between contexts are not defined.  Conceptually a transmit
1235       context behaves similar to a send-only endpoint.   A  transmit  context
1236       may  be  configured  with fewer capabilities than the base endpoint and
1237       with different attributes (such as  ordering  requirements  and  inject
1238       size)  than  other contexts associated with the same scalable endpoint.
1239       Each transmit context has its own  completion  queue.   The  number  of
1240       transmit  contexts associated with an endpoint is specified during end‐
1241       point creation.
1242
1243       The fi_tx_context call is used to retrieve a specific context,  identi‐
1244       fied  by  an  index  (see  above  for  details  on transmit context at‐
1245       tributes).  Providers may dynamically allocate contexts when fi_tx_con‐
1246       text  is called, or may statically create all contexts when fi_endpoint
1247       is invoked.  By default, a transmit context inherits the properties  of
1248       its  associated  endpoint.   However,  applications may request context
1249       specific attributes through the attr parameter.  Support for per trans‐
1250       mit  context  attributes  is  provider  specific  and  not  guaranteed.
1251       Providers will return the actual attributes  assigned  to  the  context
1252       through the attr parameter, if provided.
1253
1254   fi_rx_context
1255       Receive  contexts are independent receive queues for receiving incoming
1256       data.  Ordering and synchronization between contexts  are  not  guaran‐
1257       teed.  Conceptually a receive context behaves similar to a receive-only
1258       endpoint.  A receive context may be configured with fewer  capabilities
1259       than  the base endpoint and with different attributes (such as ordering
1260       requirements and inject size) than other contexts associated  with  the
1261       same  scalable  endpoint.   Each receive context has its own completion
1262       queue.  The number of receive contexts associated with an  endpoint  is
1263       specified during endpoint creation.
1264
1265       Receive contexts are often associated with steering flows, that specify
1266       which incoming packets targeting a scalable endpoint to process.   How‐
1267       ever,  receive  contexts  may be targeted directly by the initiator, if
1268       supported by the underlying protocol.  Such contexts are referred to as
1269       'named'.   Support  for named contexts must be indicated by setting the
1270       caps FI_NAMED_RX_CTX capability when the corresponding endpoint is cre‐
1271       ated.   Support  for named receive contexts is coordinated with address
1272       vectors.  See fi_av(3) and fi_rx_addr(3).
1273
1274       The fi_rx_context call is used to retrieve a specific context,  identi‐
1275       fied by an index (see above for details on receive context attributes).
1276       Providers may  dynamically  allocate  contexts  when  fi_rx_context  is
1277       called,  or  may statically create all contexts when fi_endpoint is in‐
1278       voked.  By default, a receive context inherits the  properties  of  its
1279       associated endpoint.  However, applications may request context specif‐
1280       ic attributes through the attr parameter.  Support for per receive con‐
1281       text  attributes  is  provider  specific and not guaranteed.  Providers
1282       will return the actual attributes assigned to the context  through  the
1283       attr parameter, if provided.
1284

SHARED CONTEXTS

1286       Shared  contexts  are  transmit  and receive contexts explicitly shared
1287       among one or more endpoints.  A shareable context allows an application
1288       to  use  a  single dedicated provider resource among multiple transport
1289       addressable endpoints.  This can greatly reduce the resources needed to
1290       manage  communication  over multiple endpoints by multiplexing transmit
1291       and/or receive processing, with the potential cost of  serializing  ac‐
1292       cess  across multiple endpoints.  Support for shareable contexts is do‐
1293       main specific.
1294
1295       Conceptually, shareable transmit contexts are transmit queues that  may
1296       be accessed by many endpoints.  The use of a shared transmit context is
1297       mostly opaque to an application.  Applications must allocate  and  bind
1298       shared  transmit  contexts  to endpoints, but operations are posted di‐
1299       rectly to the endpoint.  Shared transmit contexts  are  not  associated
1300       with completion queues or counters.  Completed operations are posted to
1301       the CQs bound to the endpoint.  An endpoint may only be associated with
1302       a single shared transmit context.
1303
1304       Unlike  shared  transmit  contexts, applications interact directly with
1305       shared receive contexts.  Users post  receive  buffers  directly  to  a
1306       shared  receive  context, with the buffers usable by any endpoint bound
1307       to the shared receive context.  Shared receive contexts are not associ‐
1308       ated  with completion queues or counters.  Completed receive operations
1309       are posted to the CQs bound to the endpoint.  An endpoint may  only  be
1310       associated  with  a single receive context, and all connectionless end‐
1311       points associated with a shared receive context  must  also  share  the
1312       same address vector.
1313
1314       Endpoints  associated  with a shared transmit context may use dedicated
1315       receive contexts, and vice-versa.  Or an endpoint may use shared trans‐
1316       mit  and  receive  contexts.  And there is no requirement that the same
1317       group of endpoints sharing a context of one type also share the context
1318       of  an  alternate type.  Furthermore, an endpoint may use a shared con‐
1319       text of one type, but a scalable set of contexts of the alternate type.
1320
1321   fi_stx_context
1322       This call is used to open a shareable transmit context (see  above  for
1323       details on the transmit context attributes).  Endpoints associated with
1324       a shared transmit context must use a subset of the  transmit  context's
1325       attributes.   Note  that  this  is  the  reverse of the requirement for
1326       transmit contexts for scalable endpoints.
1327
1328   fi_srx_context
1329       This allocates a shareable receive context (see above  for  details  on
1330       the  receive  context  attributes).  Endpoints associated with a shared
1331       receive context must use a subset of the receive context's  attributes.
1332       Note  that  this is the reverse of the requirement for receive contexts
1333       for scalable endpoints.
1334

SOCKET ENDPOINTS

1336       The following feature and description should be  considered  experimen‐
1337       tal.  Until the experimental tag is removed, the interfaces, semantics,
1338       and data structures associated with socket endpoints may change between
1339       library versions.
1340
1341       This  section  applies  to  endpoints  of  type  FI_EP_SOCK_STREAM  and
1342       FI_EP_SOCK_DGRAM, commonly referred to as socket endpoints.
1343
1344       Socket endpoints are defined with semantics that  allow  them  to  more
1345       easily  be  adopted by developers familiar with the UNIX socket API, or
1346       by middleware that exposes the socket API, while still taking advantage
1347       of high-performance hardware features.
1348
1349       The  key difference between socket endpoints and other active endpoints
1350       are socket endpoints use synchronous data  transfers.   Buffers  passed
1351       into  send and receive operations revert to the control of the applica‐
1352       tion upon returning from the function  call.   As  a  result,  no  data
1353       transfer  completions  are reported to the application, and socket end‐
1354       points are not associated with completion queues or counters.
1355
1356       Socket endpoints support  a  subset  of  message  operations:  fi_send,
1357       fi_sendv,  fi_sendmsg,  fi_recv,  fi_recvv,  fi_recvmsg, and fi_inject.
1358       Because data transfers are synchronous, the return value from send  and
1359       receive operations indicate the number of bytes transferred on success,
1360       or a negative value on error, including -FI_EAGAIN if the endpoint can‐
1361       not  send  or receive any data because of full or empty queues, respec‐
1362       tively.
1363
1364       Socket endpoints are associated with event queues and address  vectors,
1365       and  process  connection  management  events asynchronously, similar to
1366       other endpoints.  Unlike UNIX sockets, socket endpoint  must  still  be
1367       declared as either active or passive.
1368
1369       Socket endpoints behave like non-blocking sockets.  In order to support
1370       select and poll semantics, active socket endpoints are associated  with
1371       a  file  descriptor  that is signaled whenever the endpoint is ready to
1372       send and/or receive data.  The file descriptor may be  retrieved  using
1373       fi_control.
1374

OPERATION FLAGS

1376       Operation  flags  are  obtained by OR-ing the following flags together.
1377       Operation flags define the default flags applied to an endpoint's  data
1378       transfer  operations,  where  a flags parameter is not available.  Data
1379       transfer operations that take flags as input override the op_flags val‐
1380       ue of transmit or receive context attributes of an endpoint.
1381
1382       FI_COMMIT_COMPLETE
1383              Indicates  that a completion should not be generated (locally or
1384              at the peer) until the result of an  operation  have  been  made
1385              persistent.   See  fi_cq(3) for additional details on completion
1386              semantics.
1387
1388       FI_COMPLETION
1389              Indicates that a completion queue entry should  be  written  for
1390              data  transfer operations.  This flag only applies to operations
1391              issued on an endpoint that was bound to a completion queue  with
1392              the  FI_SELECTIVE_COMPLETION flag set, otherwise, it is ignored.
1393              See the fi_ep_bind section above for more detail.
1394
1395       FI_DELIVERY_COMPLETE
1396              Indicates that a completion should be generated when the  opera‐
1397              tion  has  been  processed  by the destination endpoint(s).  See
1398              fi_cq(3) for additional details on completion semantics.
1399
1400       FI_INJECT
1401              Indicates that all outbound data buffers should be  returned  to
1402              the  user's  control  immediately after a data transfer call re‐
1403              turns, even if the operation is  handled  asynchronously.   This
1404              may  require that the provider copy the data into a local buffer
1405              and transfer out of that buffer.  A provider can limit the total
1406              amount  of  send  data that may be buffered and/or the size of a
1407              single send that can use this flag.  This limit is indicated us‐
1408              ing inject_size (see inject_size above).
1409
1410       FI_INJECT_COMPLETE
1411              Indicates  that a completion should be generated when the source
1412              buffer(s) may be reused.  See fi_cq(3) for additional details on
1413              completion semantics.
1414
1415       FI_MULTICAST
1416              Indicates that data transfers will target multicast addresses by
1417              default.  Any fi_addr_t passed into a  data  transfer  operation
1418              will be treated as a multicast address.
1419
1420       FI_MULTI_RECV
1421              Applies to posted receive operations.  This flag allows the user
1422              to post a single buffer that will receive multiple incoming mes‐
1423              sages.  Received messages will be packed into the receive buffer
1424              until the buffer has been consumed.  Use of this flag may  cause
1425              a  single  posted receive operation to generate multiple comple‐
1426              tions as messages are placed into the buffer.  The placement  of
1427              received  data into the buffer may be subjected to provider spe‐
1428              cific alignment restrictions.  The buffer will  be  released  by
1429              the  provider  when  the  available buffer space falls below the
1430              specified minimum (see FI_OPT_MIN_MULTI_RECV).
1431
1432       FI_TRANSMIT_COMPLETE
1433              Indicates that a completion should be generated when the  trans‐
1434              mit operation has completed relative to the local provider.  See
1435              fi_cq(3) for additional details on completion semantics.
1436

NOTES

1438       Users should call fi_close to release all resources  allocated  to  the
1439       fabric endpoint.
1440
1441       Endpoints  allocated  with  the FI_CONTEXT or FI_CONTEXT2 mode bits set
1442       must typically provide struct fi_context(2) as their per operation con‐
1443       text  parameter.   (See fi_getinfo.3 for details.) However, when FI_SE‐
1444       LECTIVE_COMPLETION is enabled to suppress CQ completion entries, and an
1445       operation  is  initiated  without  the FI_COMPLETION flag set, then the
1446       context parameter is ignored.  An application does not need to pass  in
1447       a valid struct fi_context(2) into such data transfers.
1448
1449       Operations  that  complete  in error that are not associated with valid
1450       operational context will use the endpoint context in any error  report‐
1451       ing structures.
1452
1453       Although  applications  typically associate individual completions with
1454       either completion queues or counters, an endpoint can  be  attached  to
1455       both  a  counter and completion queue.  When combined with using selec‐
1456       tive completions, this allows an application to use counters  to  track
1457       successful  completions,  with  a CQ used to report errors.  Operations
1458       that complete with an error increment the error counter and generate  a
1459       CQ completion event.
1460
1461       As  mentioned  in  fi_getinfo(3),  the ep_attr structure can be used to
1462       query providers that support various endpoint  attributes.   fi_getinfo
1463       can return provider info structures that can support the minimal set of
1464       requirements (such that the application maintains correctness).  Howev‐
1465       er, it can also return provider info structures that exceed application
1466       requirements.   As  an  example,  consider  an  application  requesting
1467       msg_order  as  FI_ORDER_NONE.  The resulting output from fi_getinfo may
1468       have all the ordering bits set.  The application can reset the ordering
1469       bits it does not require before creating the endpoint.  The provider is
1470       free to implement a stricter ordering than is required by the  applica‐
1471       tion.
1472

RETURN VALUES

1474       Returns 0 on success.  On error, a negative value corresponding to fab‐
1475       ric errno is returned.  For fi_cancel, a return value  of  0  indicates
1476       that the cancel request was submitted for processing.
1477
1478       Fabric errno values are defined in rdma/fi_errno.h.
1479

ERRORS

1481       -FI_EDOMAIN
1482              A  resource  domain  was not bound to the endpoint or an attempt
1483              was made to bind multiple domains.
1484
1485       -FI_ENOCQ
1486              The endpoint has not been configured with necessary event queue.
1487
1488       -FI_EOPBADSTATE
1489              The endpoint's state does not permit the requested operation.
1490

SEE ALSO

1492       fi_getinfo(3),   fi_domain(3),   fi_cq(3)   fi_msg(3),    fi_tagged(3),
1493       fi_rma(3)
1494

AUTHORS

1496       OpenFabrics.
1497
1498
1499
1500Libfabric Programmer's Manual     2020-04-14                    fi_endpoint(3)
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