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    Subject[RFC PATCH net-next v2 6/7] net: ravb: Enable SW IRQ Coalescing for GbEth
    Date
    Software IRQ Coalescing is required to improve network stack performance
    in the RZ/G2L SoC family and the RZ/G3S SoC, i.e. the SoCs which use the
    GbEth IP.

    For the RZ/G2L, network throughput is comparable before and after this
    change. CPU usage during TCP RX testing dropped by 6.5% and during UDP
    RX testing dropped by 10%.

    For the RZ/G2UL, network throughput is greatly increased by this change
    (results obtained with iperf3):
    * TCP TX: 2.9% more throughput
    * TCP RX: 1.1% more throughput
    * UDP TX: similar throughput
    * UDP RX: 41500% more throughput

    For the RZ/G3S we see improvements in network throughput similar to the
    RZ/G2UL.

    The improvement of UDP RX bandwidth for the single core SoCs (RZ/G2UL &
    RZ/G3S) is particularly critical.

    Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
    ---
    drivers/net/ethernet/renesas/ravb.h | 1 +
    drivers/net/ethernet/renesas/ravb_main.c | 4 ++++
    2 files changed, 5 insertions(+)

    diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
    index 55a7a08aabef..ca7a66759e35 100644
    --- a/drivers/net/ethernet/renesas/ravb.h
    +++ b/drivers/net/ethernet/renesas/ravb.h
    @@ -1078,6 +1078,7 @@ struct ravb_hw_info {
    unsigned nc_queues:1; /* AVB-DMAC has RX and TX NC queues */
    unsigned magic_pkt:1; /* E-MAC supports magic packet detection */
    unsigned half_duplex:1; /* E-MAC supports half duplex mode */
    + unsigned needs_irq_coalesce:1; /* Requires SW IRQ Coalescing to achieve best performance */
    };

    struct ravb_private {
    diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
    index 661fd86899ac..7bb80608f260 100644
    --- a/drivers/net/ethernet/renesas/ravb_main.c
    +++ b/drivers/net/ethernet/renesas/ravb_main.c
    @@ -2639,6 +2639,7 @@ static const struct ravb_hw_info gbeth_hw_info = {
    .tx_counters = 1,
    .carrier_counters = 1,
    .half_duplex = 1,
    + .needs_irq_coalesce = 1,
    };

    static const struct of_device_id ravb_match_table[] = {
    @@ -2983,6 +2984,9 @@ static int ravb_probe(struct platform_device *pdev)
    if (info->nc_queues)
    netif_napi_add(ndev, &priv->napi[RAVB_NC], ravb_poll);

    + if (info->needs_irq_coalesce)
    + netdev_sw_irq_coalesce_default_on(ndev);
    +
    /* Network device register */
    error = register_netdev(ndev);
    if (error)
    --
    2.39.2

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