Completion Queues (CQs) and CQEs

Purpose of CQ

After a message transfer completes, either with or without error, the WQE is retired from the respective queue (SQ or RQ) and a completion notice is recorded in the CQ associated with the respective queue (SQ or RQ). The entry created in the CQ is referred to as a Completion Queue Entry, or CQE (pronounced “cookie”). Each CQE contains the 64-bit WR ID that was assigned to the original message transfer WR posted to the SQ or the RQ by software. This permits software to associate a CQE with a previously issued message transfer WR.

CQ-Related Verbs

General

The verbs that are associated with CQs are:

  • Create CQ.

  • Query CQ.

  • Resize CQ.

  • Destroy CQ.

  • Set Completion Event Handler.

  • Poll For Completion.

  • Request Completion ...

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