[dpdk-dev] [PATCH v7 4/4] net/ixgbe: use WC store to update doorbell register

[Radu Nicolau]

Performance improvement: use a write combining store
instead of a regular mmio write to update queue tail
registers.

Signed-off-by: Radu Nicolau <radu.nico...@intel.com>
---
 drivers/net/ixgbe/base/ixgbe_osdep.h   | 6 ++++++
 drivers/net/ixgbe/ixgbe_rxtx.c         | 4 ++--
 drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c | 4 ++--
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ixgbe/base/ixgbe_osdep.h 
b/drivers/net/ixgbe/base/ixgbe_osdep.h
index dc712b7..cacf724 100644
--- a/drivers/net/ixgbe/base/ixgbe_osdep.h
+++ b/drivers/net/ixgbe/base/ixgbe_osdep.h
@@ -105,6 +105,12 @@ static inline uint32_t ixgbe_read_addr(volatile void* addr)
 #define IXGBE_PCI_REG_WRITE_RELAXED(reg, value)                \
        rte_write32_relaxed((rte_cpu_to_le_32(value)), reg)
 
+#define IXGBE_PCI_REG_WC_WRITE(reg, value)                     \
+       rte_write32_wc((rte_cpu_to_le_32(value)), reg)
+
+#define IXGBE_PCI_REG_WC_WRITE_RELAXED(reg, value)             \
+       rte_write32_wc_relaxed((rte_cpu_to_le_32(value)), reg)
+
 #define IXGBE_PCI_REG_ADDR(hw, reg) \
        ((volatile uint32_t *)((char *)(hw)->hw_addr + (reg)))
 
diff --git a/drivers/net/ixgbe/ixgbe_rxtx.c b/drivers/net/ixgbe/ixgbe_rxtx.c
index 2e20e18..06e8dd5 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx.c
@@ -308,7 +308,7 @@ tx_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
 
        /* update tail pointer */
        rte_wmb();
-       IXGBE_PCI_REG_WRITE_RELAXED(txq->tdt_reg_addr, txq->tx_tail);
+       IXGBE_PCI_REG_WC_WRITE_RELAXED(txq->tdt_reg_addr, txq->tx_tail);
 
        return nb_pkts;
 }
@@ -1918,7 +1918,7 @@ ixgbe_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
                           (unsigned) nb_rx);
                rx_id = (uint16_t) ((rx_id == 0) ?
                                     (rxq->nb_rx_desc - 1) : (rx_id - 1));
-               IXGBE_PCI_REG_WRITE(rxq->rdt_reg_addr, rx_id);
+               IXGBE_PCI_REG_WC_WRITE(rxq->rdt_reg_addr, rx_id);
                nb_hold = 0;
        }
        rxq->nb_rx_hold = nb_hold;
diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c 
b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
index 517ca31..e77a7f3 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
@@ -90,7 +90,7 @@ ixgbe_rxq_rearm(struct ixgbe_rx_queue *rxq)
                             (rxq->nb_rx_desc - 1) : (rxq->rxrearm_start - 1));
 
        /* Update the tail pointer on the NIC */
-       IXGBE_PCI_REG_WRITE(rxq->rdt_reg_addr, rx_id);
+       IXGBE_PCI_REG_WC_WRITE(rxq->rdt_reg_addr, rx_id);
 }
 
 #ifdef RTE_LIBRTE_SECURITY
@@ -697,7 +697,7 @@ ixgbe_xmit_fixed_burst_vec(void *tx_queue, struct rte_mbuf 
**tx_pkts,
 
        txq->tx_tail = tx_id;
 
-       IXGBE_PCI_REG_WRITE(txq->tdt_reg_addr, txq->tx_tail);
+       IXGBE_PCI_REG_WC_WRITE(txq->tdt_reg_addr, txq->tx_tail);
 
        return nb_pkts;
 }
-- 
2.7.4