[dpdk-dev] What's the performance significance of ixgbe_recv_pkts_bulk_alloc

[Daniel Kan]

Hi,
While browsing through the ixgbe pmd code, I noticed that there is ixgbe_recv_pkts_bulk_alloc, which can be enabled if the following preconditions are met. 

     *   rxq->rx_free_thresh >= RTE_PMD_IXGBE_RX_MAX_BURST
     *   rxq->rx_free_thresh < rxq->nb_rx_desc
     *   (rxq->nb_rx_desc % rxq->rx_free_thresh) == 0
     *   rxq->nb_rx_desc<(IXGBE_MAX_RING_DESC-RTE_PMD_IXGBE_RX_MAX_BURST)

I presume the difference from the normal (non bulk) version has to do with buffer allocation. Can someone please explain the inner working of bulk_alloc and why one may or may not want to enable bulk_alloc mode? 

I only see bulk_alloc is available for ixgbe driver and not igb and e1000. Why is that?

Thanks.

Dan