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SubjectRe: [PATCH net-next] net: stmmac: add BQL support
From
On Sun, Dec 28, 2014 at 6:57 AM, Beniamino Galvani <b.galvani@gmail.com> wrote:
> Add support for Byte Queue Limits to the STMicro MAC driver.

Thank you!

> Tested on a Amlogic S805 Cortex-A5 board, where the use of BQL
> slightly decreases the ping latency from ~10ms to ~3ms when the
> 100Mbps link is saturated by TCP streams. No difference is
> observed at 1Gbps.

I see the plural. With TSQ in place it is hard (without something like
the rrul test driving multiple streams) to drive a driver to
saturation with small numbers of flows. This was with pfifo_fast, not
sch_fq, at 100mbit?

Can this board actually drive a full gigabit in the first place? Until
now most of the low end arm boards I have seen only came with
a 100mbit mac, and the gig ones lacking offloads seemed to peak
out at about 600mbit.

Under my christmas tree landed a quad core A5 (odroid-c1), also an
xgene and zedboard - both of the latter are a-needing BQL,
and I haven't booted the udroid yet. Hopefully it is the
same driver you just improved.

(https://plus.google.com/u/0/107942175615993706558/posts/f1D43umhm7E )

> Signed-off-by: Beniamino Galvani <b.galvani@gmail.com>
> ---
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 118a427..c5af3d8 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1097,6 +1097,7 @@ static int init_dma_desc_rings(struct net_device *dev, gfp_t flags)
>
> priv->dirty_tx = 0;
> priv->cur_tx = 0;
> + netdev_reset_queue(priv->dev);
>
> stmmac_clear_descriptors(priv);
>
> @@ -1300,6 +1301,7 @@ static void stmmac_dma_operation_mode(struct stmmac_priv *priv)
> static void stmmac_tx_clean(struct stmmac_priv *priv)
> {
> unsigned int txsize = priv->dma_tx_size;
> + unsigned int bytes_compl = 0, pkts_compl = 0;
>
> spin_lock(&priv->tx_lock);
>
> @@ -1356,6 +1358,8 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
> priv->hw->mode->clean_desc3(priv, p);
>
> if (likely(skb != NULL)) {
> + pkts_compl++;
> + bytes_compl += skb->len;
> dev_consume_skb_any(skb);
> priv->tx_skbuff[entry] = NULL;
> }
> @@ -1364,6 +1368,9 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
>
> priv->dirty_tx++;
> }
> +
> + netdev_completed_queue(priv->dev, pkts_compl, bytes_compl);
> +
> if (unlikely(netif_queue_stopped(priv->dev) &&
> stmmac_tx_avail(priv) > STMMAC_TX_THRESH(priv))) {
> netif_tx_lock(priv->dev);
> @@ -1418,6 +1425,7 @@ static void stmmac_tx_err(struct stmmac_priv *priv)
> (i == txsize - 1));
> priv->dirty_tx = 0;
> priv->cur_tx = 0;
> + netdev_reset_queue(priv->dev);
> priv->hw->dma->start_tx(priv->ioaddr);
>
> priv->dev->stats.tx_errors++;
> @@ -2049,6 +2057,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
> skb_tx_timestamp(skb);
>
> priv->hw->dma->enable_dma_transmission(priv->ioaddr);
> + netdev_sent_queue(dev, skb->len);
>
> spin_unlock(&priv->tx_lock);
> return NETDEV_TX_OK;
> --
> 2.1.4
>
> --
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--
Dave Täht

thttp://www.bufferbloat.net/projects/bloat/wiki/Upcoming_Talks


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