1fi_tagged(3) Libfabric v1.17.0 fi_tagged(3)
2
6 fi_tagged - Tagged data transfer operations
7 fi_trecv / fi_trecvv / fi_trecvmsg
9 Post a buffer to receive an incoming message
10 fi_tsend / fi_tsendv / fi_tsendmsg / fi_tinject / fi_tsenddata
12 Initiate an operation to send a message
13
15 #include <rdma/fi_tagged.h>
16 ssize_t fi_trecv(struct fid_ep *ep, void *buf, size_t len, void *desc,
18 fi_addr_t src_addr, uint64_t tag, uint64_t ignore, void *context);
19 ssize_t fi_trecvv(struct fid_ep *ep, const struct iovec *iov, void **desc,
21 size_t count, fi_addr_t src_addr, uint64_t tag, uint64_t ignore,
22 void *context);
23 ssize_t fi_trecvmsg(struct fid_ep *ep, const struct fi_msg_tagged *msg,
25 uint64_t flags);
26 ssize_t fi_tsend(struct fid_ep *ep, const void *buf, size_t len,
28 void *desc, fi_addr_t dest_addr, uint64_t tag, void *context);
29 ssize_t fi_tsendv(struct fid_ep *ep, const struct iovec *iov,
31 void **desc, size_t count, fi_addr_t dest_addr, uint64_t tag,
32 void *context);
33 ssize_t fi_tsendmsg(struct fid_ep *ep, const struct fi_msg_tagged *msg,
35 uint64_t flags);
36 ssize_t fi_tinject(struct fid_ep *ep, const void *buf, size_t len,
38 fi_addr_t dest_addr, uint64_t tag);
39 ssize_t fi_tsenddata(struct fid_ep *ep, const void *buf, size_t len,
41 void *desc, uint64_t data, fi_addr_t dest_addr, uint64_t tag,
42 void *context);
43 ssize_t fi_tinjectdata(struct fid_ep *ep, const void *buf, size_t len,
45 uint64_t data, fi_addr_t dest_addr, uint64_t tag);
46
48 fid Fabric endpoint on which to initiate tagged communication opera‐
49 tion.
50 buf Data buffer to send or receive.
52 len Length of data buffer to send or receive.
54 iov Vectored data buffer.
56 count Count of vectored data entries.
58 tag Tag associated with the message.
60 ignore Mask of bits to ignore applied to the tag for receive opera‐
62 tions.
63 desc Memory descriptor associated with the data buffer. See
65 fi_mr(3).
66 data Remote CQ data to transfer with the sent data.
68 dest_addr
70 Destination address for connectionless transfers. Ignored for
71 connected endpoints.
72 src_addr
74 Source address to receive from for connectionless transfers.
75 Applies only to connectionless endpoints with the FI_DIRECT‐
76 ED_RECV capability enabled, otherwise this field is ignored. If
77 set to FI_ADDR_UNSPEC, any source address may match.
78 msg Message descriptor for send and receive operations.
80 flags Additional flags to apply for the send or receive operation.
82 context
84 User specified pointer to associate with the operation. This
85 parameter is ignored if the operation will not generate a suc‐
86 cessful completion, unless an op flag specifies the context pa‐
87 rameter be used for required input.
88
90 Tagged messages are data transfers which carry a key or tag with the
91 message buffer. The tag is used at the receiving endpoint to match the
92 incoming message with a corresponding receive buffer. Message tags
93 match when the receive buffer tag is the same as the send buffer tag
94 with the ignored bits masked out. This can be stated as:
95 send_tag & ~ignore == recv_tag & ~ignore
97 In general, message tags are checked against receive buffers in the or‐
99 der in which messages have been posted to the endpoint. See the order‐
100 ing discussion below for more details.
101 The send functions – fi_tsend, fi_tsendv, fi_tsendmsg, fi_tinject, and
103 fi_tsenddata – are used to transmit a tagged message from one endpoint
104 to another endpoint. The main difference between send functions are
105 the number and type of parameters that they accept as input. Other‐
106 wise, they perform the same general function.
107 The receive functions – fi_trecv, fi_trecvv, fi_recvmsg – post a data
109 buffer to an endpoint to receive inbound tagged messages. Similar to
110 the send operations, receive operations operate asynchronously. Users
111 should not touch the posted data buffer(s) until the receive operation
112 has completed. Posted receive buffers are matched with inbound send
113 messages based on the tags associated with the send and receive buf‐
114 fers.
115 An endpoint must be enabled before an application can post send or re‐
117 ceive operations to it. For connected endpoints, receive buffers may
118 be posted prior to connect or accept being called on the endpoint.
119 This ensures that buffers are available to receive incoming data imme‐
120 diately after the connection has been established.
121 Completed message operations are reported to the user through one or
123 more event collectors associated with the endpoint. Users provide con‐
124 text which are associated with each operation, and is returned to the
125 user as part of the event completion. See fi_cq for completion event
126 details.
127 fi_tsend
129 The call fi_tsend transfers the data contained in the user-specified
130 data buffer to a remote endpoint, with message boundaries being main‐
131 tained. The local endpoint must be connected to a remote endpoint or
132 destination before fi_tsend is called. Unless the endpoint has been
133 configured differently, the data buffer passed into fi_tsend must not
134 be touched by the application until the fi_tsend call completes asyn‐
135 chronously.
136 fi_tsendv
138 The fi_tsendv call adds support for a scatter-gather list to fi_tsend.
139 The fi_sendv transfers the set of data buffers referenced by the iov
140 parameter to a remote endpoint as a single message.
141 fi_tsendmsg
143 The fi_tsendmsg call supports data transfers over both connected and
144 connectionless endpoints, with the ability to control the send opera‐
145 tion per call through the use of flags. The fi_tsendmsg function takes
146 a struct fi_msg_tagged as input.
147 struct fi_msg_tagged {
149 const struct iovec *msg_iov; /* scatter-gather array */
150 void *desc; /* data descriptor */
151 size_t iov_count;/* # elements in msg_iov */
152 fi_addr_t addr; /* optional endpoint address */
153 uint64_t tag; /* tag associated with message */
154 uint64_t ignore; /* mask applied to tag for receives */
155 void *context; /* user-defined context */
156 uint64_t data; /* optional immediate data */
157 };
158 fi_tinject
160 The tagged inject call is an optimized version of fi_tsend. It pro‐
161 vides similar completion semantics as fi_inject fi_msg(3).
162 fi_tsenddata
164 The tagged send data call is similar to fi_tsend, but allows for the
165 sending of remote CQ data (see FI_REMOTE_CQ_DATA flag) as part of the
166 transfer.
167 fi_tinjectdata
169 The tagged inject data call is similar to fi_tinject, but allows for
170 the sending of remote CQ data (see FI_REMOTE_CQ_DATA flag) as part of
171 the transfer.
172 fi_trecv
174 The fi_trecv call posts a data buffer to the receive queue of the cor‐
175 responding endpoint. Posted receives are searched in the order in
176 which they were posted in order to match sends. Message boundaries are
177 maintained. The order in which the receives complete is dependent on
178 the endpoint type and protocol.
179 fi_trecvv
181 The fi_trecvv call adds support for a scatter-gather list to fi_trecv.
182 The fi_trecvv posts the set of data buffers referenced by the iov pa‐
183 rameter to a receive incoming data.
184 fi_trecvmsg
186 The fi_trecvmsg call supports posting buffers over both connected and
187 connectionless endpoints, with the ability to control the receive oper‐
188 ation per call through the use of flags. The fi_trecvmsg function
189 takes a struct fi_msg_tagged as input.
190
192 The fi_trecvmsg and fi_tsendmsg calls allow the user to specify flags
193 which can change the default message handling of the endpoint. Flags
194 specified with fi_trecvmsg / fi_tsendmsg override most flags previously
195 configured with the endpoint, except where noted (see fi_endpoint).
196 The following list of flags are usable with fi_trecvmsg and/or
197 fi_tsendmsg.
198 FI_REMOTE_CQ_DATA
200 Applies to fi_tsendmsg and fi_tsenddata. Indicates that remote
201 CQ data is available and should be sent as part of the request.
202 See fi_getinfo for additional details on FI_REMOTE_CQ_DATA.
203 FI_COMPLETION
205 Indicates that a completion entry should be generated for the
206 specified operation. The endpoint must be bound to a completion
207 queue with FI_SELECTIVE_COMPLETION that corresponds to the spec‐
208 ified operation, or this flag is ignored.
209 FI_MORE
211 Indicates that the user has additional requests that will imme‐
212 diately be posted after the current call returns. Use of this
213 flag may improve performance by enabling the provider to opti‐
214 mize its access to the fabric hardware.
215 FI_INJECT
217 Applies to fi_tsendmsg. Indicates that the outbound data buffer
218 should be returned to user immediately after the send call re‐
219 turns, even if the operation is handled asynchronously. This
220 may require that the underlying provider implementation copy the
221 data into a local buffer and transfer out of that buffer. This
222 flag can only be used with messages smaller than inject_size.
223 FI_INJECT_COMPLETE
225 Applies to fi_tsendmsg. Indicates that a completion should be
226 generated when the source buffer(s) may be reused.
227 FI_TRANSMIT_COMPLETE
229 Applies to fi_tsendmsg. Indicates that a completion should not
230 be generated until the operation has been successfully transmit‐
231 ted and is no longer being tracked by the provider.
232 FI_MATCH_COMPLETE
234 Applies to fi_tsendmsg. Indicates that a completion should be
235 generated only after the message has either been matched with a
236 tagged buffer or was discarded by the target application.
237 FI_FENCE
239 Applies to transmits. Indicates that the requested operation,
240 also known as the fenced operation, and any operation posted af‐
241 ter the fenced operation will be deferred until all previous op‐
242 erations targeting the same peer endpoint have completed. Oper‐
243 ations posted after the fencing will see and/or replace the re‐
244 sults of any operations initiated prior to the fenced operation.
245 The ordering of operations starting at the posting of the fenced opera‐
247 tion (inclusive) to the posting of a subsequent fenced operation (ex‐
248 clusive) is controlled by the endpoint’s ordering semantics.
249 The following flags may be used with fi_trecvmsg.
251 FI_PEEK
253 The peek flag may be used to see if a specified message has ar‐
254 rived. A peek request is often useful on endpoints that have
255 provider allocated buffering enabled (see fi_rx_attr to‐
256 tal_buffered_recv). Unlike standard receive operations, a re‐
257 ceive operation with the FI_PEEK flag set does not remain queued
258 with the provider after the peek completes successfully. The
259 peek operation operates asynchronously, and the results of the
260 peek operation are available in the completion queue associated
261 with the endpoint. If no message is found matching the tags
262 specified in the peek request, then a completion queue error en‐
263 try with err field set to FI_ENOMSG will be available.
264 If a peek request locates a matching message, the operation will com‐
266 plete successfully. The returned completion data will indicate the
267 meta-data associated with the message, such as the message length, com‐
268 pletion flags, available CQ data, tag, and source address. The data
269 available is subject to the completion entry format (e.g. struct
270 fi_cq_tagged_entry).
271 An application may supply a buffer if it desires to receive data as a
273 part of the peek operation. In order to receive data as a part of the
274 peek operation, the buf and len fields must be available in the CQ for‐
275 mat. In particular, FI_CQ_FORMAT_CONTEXT and FI_CQ_FORMAT_MSG cannot
276 be used if peek operations desire to obtain a copy of the data. The
277 returned data is limited to the size of the input buffer(s) or the mes‐
278 sage size, if smaller. A provider indicates if data is available by
279 setting the buf field of the CQ entry to the user’s first input buffer.
280 If buf is NULL, no data was available to return. A provider may return
281 NULL even if the peek operation completes successfully. Note that the
282 CQ entry len field will reference the size of the message, not neces‐
283 sarily the size of the returned data.
284 FI_CLAIM
286 If this flag is used in conjunction with FI_PEEK, it indicates
287 if the peek request completes successfully – indicating that a
288 matching message was located – the message is claimed by caller.
289 Claimed messages can only be retrieved using a subsequent,
290 paired receive operation with the FI_CLAIM flag set. A receive
291 operation with the FI_CLAIM flag set, but FI_PEEK not set is
292 used to retrieve a previously claimed message.
293 In order to use the FI_CLAIM flag, an application must supply a struct
295 fi_context structure as the context for the receive operation, or a
296 struct fi_recv_context in the case of buffered receives. The same
297 fi_context structure used for an FI_PEEK + FI_CLAIM operation must be
298 used by the paired FI_CLAIM request.
299 This flag also applies to endpoints configured for FI_BUFFERED_RECV or
301 FI_VARIABLE_MSG. When set, it is used to retrieve a tagged message
302 that was buffered by the provider. See Buffered Tagged Receives sec‐
303 tion for details.
304 FI_DISCARD
306 This flag may be used in conjunction with either FI_PEEK or
307 FI_CLAIM. If this flag is used in conjunction with FI_PEEK, it
308 indicates if the peek request completes successfully – indicat‐
309 ing that a matching message was located – the message is dis‐
310 carded by the provider, as the data is not needed by the appli‐
311 cation. This flag may also be used in conjunction with FI_CLAIM
312 in order to discard a message previously claimed using an
313 FI_PEEK + FI_CLAIM request.
314 This flag also applies to endpoints configured for FI_BUFFERED_RECV or
316 FI_VARIABLE_MSG. When set, it indicates that the provider should free
317 a buffered messages. See Buffered Tagged Receives section for details.
318 If this flag is set, the input buffer(s) and length parameters are ig‐
320 nored.
321
323 See fi_msg(3) for an introduction to buffered receives. The handling
324 of buffered receives differs between fi_msg operations and fi_tagged.
325 Although the provider is responsible for allocating and managing net‐
326 work buffers, the application is responsible for identifying the tags
327 that will be used to match incoming messages. The provider handles
328 matching incoming receives to the application specified tags.
329 When FI_BUFFERED_RECV is enabled, the application posts the tags that
331 will be used for matching purposes. Tags are posted using fi_trecv,
332 fi_trecvv, and fi_trecvmsg; however, parameters related to the input
333 buffers are ignored (e.g. buf, len, iov, desc). When a provider re‐
334 ceives a message for which there is a matching tag, it will write an
335 entry to the completion queue associated with the receiving endpoint.
336 For discussion purposes, the completion queue is assumed to be config‐
338 ured for FI_CQ_FORMAT_TAGGED. The op_context field will point to a
339 struct fi_recv_context.
340 struct fi_recv_context {
342 struct fid_ep *ep;
343 void *context;
344 };
345 The `ep' field will be NULL. The `context' field will match the appli‐
347 cation context specified when posting the tag. Other fields are set as
348 defined in fi_msg(3).
349 After being notified that a buffered receive has arrived, applications
351 must either claim or discard the message as described in fi_msg(3).
352
354 Variable length messages are defined in fi_msg(3). The requirements
355 for handling variable length tagged messages is identical to those de‐
356 fined above for buffered tagged receives.
357
359 The tagged send and receive calls return 0 on success. On error, a
360 negative value corresponding to fabric errno is returned. Fabric er‐
361 rno values are defined in fi_errno.h.
362
364 -FI_EAGAIN
365 See fi_msg(3) for a detailed description of handling FI_EAGAIN.
366 -FI_EINVAL
368 Indicates that an invalid argument was supplied by the user.
369 -FI_EOTHER
371 Indicates that an unspecified error occurred.
372
374 fi_getinfo(3), fi_endpoint(3), fi_domain(3), fi_cq(3)
375
377 OpenFabrics.
378Libfabric Programmer’s Manual 2022-12-11 fi_tagged(3)