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

ibv_poll_cq - poll a completion queue (CQ)

#include <infiniband/verbs.h>

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

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 */ union {
__be32 imm_data; /* Immediate data (in network byte order) */ uint32_t invalidated_rkey; /* Local RKey that was invalidated */
}; 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) */ unsigned 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:

verified. Valid only when device_cap_flags in device_attr indicates current QP is supported by checksum offload.

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.

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

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.

IBV_WC_DRIVER1 will be reported as a response to IBV_WR_DRIVER1 opcode; IBV_WC_DRIVER2/IBV_WC_DRIVER3 will be reported on specific driver operations.

ibv_post_send(3), ibv_post_recv(3)

2006-10-31 libibverbs