[dpdk-dev] [PATCH][v2] net/af_xdp: avoid to unnecessary allocation and free mbuf in rx path

[Li RongQing <lirongqing@baidu.com>]

when receive packets, the max bunch number of mbuf are allocated
if hardware does not receive the max bunch number packets, it
will free redundancy mbuf, that is low-performance

so optimize rx performance, by allocating number of mbuf based on
result of xsk_ring_cons__peek, to avoid to redundancy allocation,
and free mbuf when receive packets

V2: rollback rx cached_cons if mbuf failed to be allocated

Signed-off-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: Dongsheng Rong <rongdongsheng@baidu.com>
---
 drivers/net/af_xdp/rte_eth_af_xdp.c | 67 ++++++++++++++++---------------------
 1 file changed, 29 insertions(+), 38 deletions(-)

diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
index 01f462b46..e04fa43f6 100644
--- a/drivers/net/af_xdp/rte_eth_af_xdp.c
+++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
@@ -251,28 +251,29 @@ af_xdp_rx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 	struct xsk_umem_info *umem = rxq->umem;
 	uint32_t idx_rx = 0;
 	unsigned long rx_bytes = 0;
-	int rcvd, i;
+	int i;
 	struct rte_mbuf *fq_bufs[ETH_AF_XDP_RX_BATCH_SIZE];
 
-	/* allocate bufs for fill queue replenishment after rx */
-	if (rte_pktmbuf_alloc_bulk(umem->mb_pool, fq_bufs, nb_pkts)) {
-		AF_XDP_LOG(DEBUG,
-			"Failed to get enough buffers for fq.\n");
-		return 0;
-	}
+	nb_pkts = xsk_ring_cons__peek(rx, nb_pkts, &idx_rx);
 
-	rcvd = xsk_ring_cons__peek(rx, nb_pkts, &idx_rx);
-
-	if (rcvd == 0) {
+	if (nb_pkts == 0) {
 #if defined(XDP_USE_NEED_WAKEUP)
 		if (xsk_ring_prod__needs_wakeup(fq))
 			(void)poll(rxq->fds, 1, 1000);
 #endif
 
-		goto out;
+		return 0;
+	}
+
+	/* allocate bufs for fill queue replenishment after rx */
+	if (rte_pktmbuf_alloc_bulk(umem->mb_pool, fq_bufs, nb_pkts)) {
+		AF_XDP_LOG(DEBUG,
+			"Failed to get enough buffers for fq.\n");
+		rx->cached_cons -= nb_pkts;
+		return 0;
 	}
 
-	for (i = 0; i < rcvd; i++) {
+	for (i = 0; i < nb_pkts; i++) {
 		const struct xdp_desc *desc;
 		uint64_t addr;
 		uint32_t len;
@@ -297,20 +298,14 @@ af_xdp_rx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 		rx_bytes += len;
 	}
 
-	xsk_ring_cons__release(rx, rcvd);
-
-	(void)reserve_fill_queue(umem, rcvd, fq_bufs, fq);
+	xsk_ring_cons__release(rx, nb_pkts);
+	(void)reserve_fill_queue(umem, nb_pkts, fq_bufs, fq);
 
 	/* statistics */
-	rxq->stats.rx_pkts += rcvd;
+	rxq->stats.rx_pkts += nb_pkts;
 	rxq->stats.rx_bytes += rx_bytes;
 
-out:
-	if (rcvd != nb_pkts)
-		rte_mempool_put_bulk(umem->mb_pool, (void **)&fq_bufs[rcvd],
-				     nb_pkts - rcvd);
-
-	return rcvd;
+	return nb_pkts;
 }
 #else
 static uint16_t
@@ -322,7 +317,7 @@ af_xdp_rx_cp(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 	struct xsk_ring_prod *fq = &rxq->fq;
 	uint32_t idx_rx = 0;
 	unsigned long rx_bytes = 0;
-	int rcvd, i;
+	int i;
 	uint32_t free_thresh = fq->size >> 1;
 	struct rte_mbuf *mbufs[ETH_AF_XDP_RX_BATCH_SIZE];
 
@@ -330,20 +325,21 @@ af_xdp_rx_cp(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 		(void)reserve_fill_queue(umem, ETH_AF_XDP_RX_BATCH_SIZE,
 					 NULL, fq);
 
-	if (unlikely(rte_pktmbuf_alloc_bulk(rxq->mb_pool, mbufs, nb_pkts) != 0))
-		return 0;
-
-	rcvd = xsk_ring_cons__peek(rx, nb_pkts, &idx_rx);
-	if (rcvd == 0) {
+	nb_pkts = xsk_ring_cons__peek(rx, nb_pkts, &idx_rx);
+	if (nb_pkts == 0) {
 #if defined(XDP_USE_NEED_WAKEUP)
 		if (xsk_ring_prod__needs_wakeup(fq))
 			(void)poll(rxq->fds, 1, 1000);
 #endif
+		return 0;
+	}
 
-		goto out;
+	if (unlikely(rte_pktmbuf_alloc_bulk(rxq->mb_pool, mbufs, nb_pkts))) {
+		rx->cached_cons -= nb_pkts;
+		return 0;
 	}
 
-	for (i = 0; i < rcvd; i++) {
+	for (i = 0; i < nb_pkts; i++) {
 		const struct xdp_desc *desc;
 		uint64_t addr;
 		uint32_t len;
@@ -362,18 +358,13 @@ af_xdp_rx_cp(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 		bufs[i] = mbufs[i];
 	}
 
-	xsk_ring_cons__release(rx, rcvd);
+	xsk_ring_cons__release(rx, nb_pkts);
 
 	/* statistics */
-	rxq->stats.rx_pkts += rcvd;
+	rxq->stats.rx_pkts += nb_pkts;
 	rxq->stats.rx_bytes += rx_bytes;
 
-out:
-	if (rcvd != nb_pkts)
-		rte_mempool_put_bulk(rxq->mb_pool, (void **)&mbufs[rcvd],
-				     nb_pkts - rcvd);
-
-	return rcvd;
+	return nb_pkts;
 }
 #endif
 
-- 
2.16.2