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ibv_poll_cq(3) [debian man page]

IBV_POLL_CQ(3)						  Libibverbs Programmer's Manual					    IBV_POLL_CQ(3)

NAME

       ibv_poll_cq - poll a completion queue (CQ)

SYNOPSIS

       #include <infiniband/verbs.h>

       int ibv_poll_cq(struct ibv_cq *cq, int num_entries,
		       struct ibv_wc *wc);

DESCRIPTION

       ibv_poll_cq() polls the CQ cq for work completions and returns the first num_entries (or all available completions if the CQ contains fewer
       than this number) in the array wc.  The argument wc is a pointer to an array of ibv_wc structs, as defined in <infiniband/verbs.h>.

       struct ibv_wc {
	       uint64_t 	       wr_id;	       /* ID of the completed Work Request (WR) */
	       enum ibv_wc_status      status;	       /* Status of the operation */
	       enum ibv_wc_opcode      opcode;	       /* Operation type specified in the completed WR */
	       uint32_t 	       vendor_err;     /* Vendor error syndrome */
	       uint32_t 	       byte_len;       /* Number of bytes transferred */
	       uint32_t 	       imm_data;       /* Immediate data (in network byte order) */
	       uint32_t 	       qp_num;	       /* Local QP number of completed WR */
	       uint32_t 	       src_qp;	       /* Source QP number (remote QP number) of completed WR (valid only for UD QPs) */
	       int		       wc_flags;       /* Flags of the completed WR */
	       uint16_t 	       pkey_index;     /* P_Key index (valid only for GSI QPs) */
	       uint16_t 	       slid;	       /* Source LID */
	       uint8_t		       sl;	       /* Service Level */
	       uint8_t		       dlid_path_bits; /* DLID path bits (not applicable for multicast messages) */
       };

       The attribute wc_flags describes the properties of the work completion.	It is either 0 or the bitwise OR of one or more of  the  following
       flags:

       IBV_WC_GRH  GRH is present (valid only for UD QPs)

       IBV_WC_WITH_IMM	Immediate data value is valid

       Not  all  wc  attributes  are always valid. If the completion status is other than IBV_WC_SUCCESS, only the following attributes are valid:
       wr_id, status, qp_num, and vendor_err.

RETURN VALUE

       On success, ibv_poll_cq() returns a non-negative value equal to the number of completions found.  On failure, a negative value is returned.

NOTES

       Each polled completion is removed from the CQ and cannot be returned to it.

       The user should consume work completions at a rate that prevents CQ overrun from occurrence.  In case of a  CQ  overrun,  the  async  event
       IBV_EVENT_CQ_ERR will be triggered, and the CQ cannot be used.

SEE ALSO

       ibv_post_send(3), ibv_post_recv(3)

AUTHORS

       Dotan Barak <dotanba@gmail.com>

libibverbs							    2006-10-31							    IBV_POLL_CQ(3)

Check Out this Related Man Page

IBV_POST_RECV(3)					  Libibverbs Programmer's Manual					  IBV_POST_RECV(3)

NAME

       ibv_post_recv - post a list of work requests (WRs) to a receive queue

SYNOPSIS

       #include <infiniband/verbs.h>

       int ibv_post_recv(struct ibv_qp *qp, struct ibv_recv_wr *wr,
			 struct ibv_recv_wr **bad_wr);

DESCRIPTION

       ibv_post_recv() posts the linked list of work requests (WRs) starting with wr to the receive queue of the queue pair qp.  It stops process-
       ing WRs from this list at the first failure (that can be detected immediately while requests are being posted), and returns this failing WR
       through bad_wr.

       The argument wr is an ibv_recv_wr struct, as defined in <infiniband/verbs.h>.

       struct ibv_recv_wr {
	       uint64_t 	       wr_id;	  /* User defined WR ID */
	       struct ibv_recv_wr     *next;	  /* Pointer to next WR in list, NULL if last WR */
	       struct ibv_sge	      *sg_list;   /* Pointer to the s/g array */
	       int		       num_sge;   /* Size of the s/g array */
       };

       struct ibv_sge {
	       uint64_t 	       addr;	  /* Start address of the local memory buffer */
	       uint32_t 	       length;	  /* Length of the buffer */
	       uint32_t 	       lkey;	  /* Key of the local Memory Region */
       };

RETURN VALUE

       ibv_post_recv() returns 0 on success, or the value of errno on failure (which indicates the failure reason).

NOTES

       The buffers used by a WR can only be safely reused after WR the request is fully executed and a work completion has been retrieved from the
       corresponding completion queue (CQ).

       If the QP qp is associated with a shared receive queue, you must use the function ibv_post_srq_recv(), and not ibv_post_recv(),	since  the
       QP's own receive queue will not be used.

       If  a  WR  is  being posted to a UD QP, the Global Routing Header (GRH) of the incoming message will be placed in the first 40 bytes of the
       buffer(s) in the scatter list.  If no GRH is present in the incoming message, then the first bytes will be undefined.  This means  that	in
       all cases, the actual data of the incoming message will start at an offset of 40 bytes into the buffer(s) in the scatter list.

SEE ALSO

       ibv_create_qp(3), ibv_post_send(3), ibv_post_srq_recv(3), ibv_poll_cq(3)

AUTHORS

       Dotan Barak <dotanba@gmail.com>

libibverbs							    2006-10-31							  IBV_POST_RECV(3)
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