net/ena: rework getting number of available descriptors

ena_com API should be preferred for getting number of used/available
descriptors unless extra calculation needs to be performed.

Some helper variables were added for storing values that are later
reused. Moreover, for limiting the value of sent/received packets to
the number of available descriptors, the RTE_MIN is used instead of
if function, which was doing similar thing but was less descriptive.

Signed-off-by: Michal Krawczyk <mk@semihalf.com>
Reviewed-by: Igor Chauskin <igorch@amazon.com>
Reviewed-by: Guy Tzalik <gtzalik@amazon.com>

diff --git a/drivers/net/ena/ena_ethdev.c b/drivers/net/ena/ena_ethdev.c
index e43ba51..9d76ebb 100644 (file)
--- a/drivers/net/ena/ena_ethdev.c
+++ b/drivers/net/ena/ena_ethdev.c
@@ -1426,7 +1426,8 @@ static int ena_populate_rx_queue(struct ena_ring *rxq, unsigned int count)
        if (unlikely(!count))
                return 0;
 
-       in_use = rxq->next_to_use - rxq->next_to_clean;
+       in_use = ring_size - ena_com_free_q_entries(rxq->ena_com_io_sq) - 1;
+
        ena_assert_msg(((in_use + count) < ring_size), "bad ring state\n");
 
        /* get resources for incoming packets */
@@ -2145,8 +2146,9 @@ static uint16_t eth_ena_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
        struct ena_ring *rx_ring = (struct ena_ring *)(rx_queue);
        unsigned int ring_size = rx_ring->ring_size;
        unsigned int ring_mask = ring_size - 1;
+       unsigned int refill_required;
        uint16_t next_to_clean = rx_ring->next_to_clean;
-       uint16_t desc_in_use = 0;
+       uint16_t descs_in_use;
        struct rte_mbuf *mbuf;
        uint16_t completed;
        struct ena_com_rx_ctx ena_rx_ctx;
@@ -2159,9 +2161,9 @@ static uint16_t eth_ena_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
                return 0;
        }
 
-       desc_in_use = rx_ring->next_to_use - next_to_clean;
-       if (unlikely(nb_pkts > desc_in_use))
-               nb_pkts = desc_in_use;
+       descs_in_use = ring_size -
+               ena_com_free_q_entries(rx_ring->ena_com_io_sq) - 1;
+       nb_pkts = RTE_MIN(descs_in_use, nb_pkts);
 
        for (completed = 0; completed < nb_pkts; completed++) {
                ena_rx_ctx.max_bufs = rx_ring->sgl_size;
@@ -2213,11 +2215,11 @@ static uint16_t eth_ena_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
        rx_ring->rx_stats.cnt += completed;
        rx_ring->next_to_clean = next_to_clean;
 
-       desc_in_use = desc_in_use - completed + 1;
+       refill_required = ena_com_free_q_entries(rx_ring->ena_com_io_sq);
        /* Burst refill to save doorbells, memory barriers, const interval */
-       if (ring_size - desc_in_use > ENA_RING_DESCS_RATIO(ring_size)) {
+       if (refill_required > ENA_RING_DESCS_RATIO(ring_size)) {
                ena_com_update_dev_comp_head(rx_ring->ena_com_io_cq);
-               ena_populate_rx_queue(rx_ring, ring_size - desc_in_use);
+               ena_populate_rx_queue(rx_ring, refill_required);
        }
 
        return completed;
@@ -2360,7 +2362,7 @@ static uint16_t eth_ena_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
        struct ena_tx_buffer *tx_info;
        struct ena_com_buf *ebuf;
        uint16_t rc, req_id, total_tx_descs = 0;
-       uint16_t sent_idx = 0, empty_tx_reqs;
+       uint16_t sent_idx = 0;
        uint16_t push_len = 0;
        uint16_t delta = 0;
        int nb_hw_desc;
@@ -2373,9 +2375,8 @@ static uint16_t eth_ena_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
                return 0;
        }
 
-       empty_tx_reqs = ring_size - (next_to_use - next_to_clean);
-       if (nb_pkts > empty_tx_reqs)
-               nb_pkts = empty_tx_reqs;
+       nb_pkts = RTE_MIN(ena_com_free_q_entries(tx_ring->ena_com_io_sq),
+               nb_pkts);
 
        for (sent_idx = 0; sent_idx < nb_pkts; sent_idx++) {
                mbuf = tx_pkts[sent_idx];