net/bnxt: remove software prefetches from AVX2 Rx

Testing has shown no performance benefit from software prefetching
of receive completion descriptors in the AVX2 burst receive path,
and slightly better performance without them on some CPU families,
so this patch removes them.

Fixes: c4e4c18963b0 ("net/bnxt: add AVX2 RX/Tx")
Cc: stable@dpdk.org
Signed-off-by: Lance Richardson <lance.richardson@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>

diff --git a/drivers/net/bnxt/bnxt_rxtx_vec_avx2.c b/drivers/net/bnxt/bnxt_rxtx_vec_avx2.c
index 54e3af2..34bd22e 100644 (file)
--- a/drivers/net/bnxt/bnxt_rxtx_vec_avx2.c
+++ b/drivers/net/bnxt/bnxt_rxtx_vec_avx2.c
@@ -92,12 +92,6 @@ recv_burst_vec_avx2(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts)
        cons = raw_cons & (cp_ring_size - 1);
        mbcons = (raw_cons / 2) & (rx_ring_size - 1);
 
-       /* Prefetch first four descriptor pairs. */
-       rte_prefetch0(&cp_desc_ring[cons + 0]);
-       rte_prefetch0(&cp_desc_ring[cons + 4]);
-       rte_prefetch0(&cp_desc_ring[cons + 8]);
-       rte_prefetch0(&cp_desc_ring[cons + 12]);
-
        /* Return immediately if there is not at least one completed packet. */
        if (!bnxt_cpr_cmp_valid(&cp_desc_ring[cons], raw_cons, cp_ring_size))
                return 0;
@@ -136,14 +130,6 @@ recv_burst_vec_avx2(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts)
                _mm256_storeu_si256((void *)&rx_pkts[i + 4], t0);
 #endif
 
-               /* Prefetch eight descriptor pairs for next iteration. */
-               if (i + BNXT_RX_DESCS_PER_LOOP_VEC256 < nb_pkts) {
-                       rte_prefetch0(&cp_desc_ring[cons + 16]);
-                       rte_prefetch0(&cp_desc_ring[cons + 20]);
-                       rte_prefetch0(&cp_desc_ring[cons + 24]);
-                       rte_prefetch0(&cp_desc_ring[cons + 28]);
-               }
-
                /*
                 * Load eight receive completion descriptors into 256-bit
                 * registers. Loads are issued in reverse order in order to