net/sfc: avoid dummy writes to Rx queue state structure

If there is no packets to be processed, it does not make sense
to write the same values back to Rx queue structure.

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Ivan Malov <ivan.malov@oktetlabs.ru>

diff --git a/drivers/net/sfc/sfc_ef10_rx.c b/drivers/net/sfc/sfc_ef10_rx.c
index 8d0e69c..0986102 100644 (file)
--- a/drivers/net/sfc/sfc_ef10_rx.c
+++ b/drivers/net/sfc/sfc_ef10_rx.c
@@ -191,14 +191,18 @@ sfc_ef10_rx_prepared(struct sfc_ef10_rxq *rxq, struct rte_mbuf **rx_pkts,
                     uint16_t nb_pkts)
 {
        uint16_t n_rx_pkts = RTE_MIN(nb_pkts, rxq->prepared);
-       unsigned int completed = rxq->completed;
-       unsigned int i;
 
-       rxq->prepared -= n_rx_pkts;
-       rxq->completed = completed + n_rx_pkts;
+       if (n_rx_pkts != 0) {
+               unsigned int completed = rxq->completed;
 
-       for (i = 0; i < n_rx_pkts; ++i, ++completed)
-               rx_pkts[i] = rxq->sw_ring[completed & rxq->ptr_mask].mbuf;
+               rxq->prepared -= n_rx_pkts;
+               rxq->completed = completed + n_rx_pkts;
+
+               do {
+                       *rx_pkts++ =
+                               rxq->sw_ring[completed++ & rxq->ptr_mask].mbuf;
+               } while (completed != rxq->completed);
+       }
 
        return n_rx_pkts;
 }