linux-kernel - Re: [PATCH v2] net: stmmac: add BQL support

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Date:	Thu, 22 Jan 2015 12:58:02 +0100
From:	Giuseppe CAVALLARO <peppe.cavallaro@...com>
To:	Beniamino Galvani <b.galvani@...il.com>,
	"David S. Miller" <davem@...emloft.net>
Cc:	Florian Fainelli <f.fainelli@...il.com>,
	Dave Taht <dave.taht@...il.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] net: stmmac: add BQL support

On 1/21/2015 7:07 PM, Beniamino Galvani wrote:
> Add support for Byte Queue Limits to the STMicro MAC driver.
>
> Tested on a Amlogic S802 quad Cortex-A9 board, where the use of BQL
> decreases the latency of a high priority ping from ~12ms to ~1ms when
> the 100Mbit link is saturated by 20 TCP streams.
>
> Signed-off-by: Beniamino Galvani <b.galvani@...il.com>


Ciao Beniamino

thx for the patch, I also see some improvements on my side

Acked-by: Giuseppe Cavallaro <peppe.cavallaro@...com>

> ---
> Changes since v1:
>   - don't access skb->len after the start of DMA transmission in
>     stmmac_xmit(), to avoid potential use after free in case tx_lock is
>     removed in the future
>
>   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..1d74313 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++;
> @@ -2048,6 +2056,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
>   	if (!priv->hwts_tx_en)
>   		skb_tx_timestamp(skb);
>
> +	netdev_sent_queue(dev, skb->len);
>   	priv->hw->dma->enable_dma_transmission(priv->ioaddr);
>
>   	spin_unlock(&priv->tx_lock);
>

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