Sending packets using optimized pio write sequences without sfences and out of order credit returns

Abstract

Methods and apparatus for sending packets using optimized PIO write sequences without sfences and out-of-order credit returns. Sequences of Programmed Input/Output (PIO) write instructions to write packet data to a PIO send memory are received by a processor in an original order and executed out of order, resulting in the packet data being written to send blocks in the PIO send memory out of order, while the packets themselves are stored in sequential order once all of the packet data is written. The packets are egressed out of order by egressing packet data contained in the send blocks to an egress block using a non-sequential packet order that is different than the sequential packet order. In conjunction with egressing the packets, corresponding credits are returned in the non-sequential packet order. A block list comprising a linked list and a free list are used to facilitate out-of-order packet egress and corresponding out-of-order credit returns.