Dear Sir.
have any suggestion?
Best Regards.
2015-06-05 18:09 GMT+08:00 Mingyu Li <igv...@gmail.com>:
> this feature i reference tg3.c driver at function tg3_start_xmit.
> it says therer is a small possibility that start_xmit will miss it
> and cause the queue to be stopped forever.
>
> below is the tg3 drivers code
> === function tg3_tx ===
> tnapi->tx_cons = sw_idx;
>
> /* Need to make the tx_cons update visible to tg3_start_xmit()
> * before checking for netif_queue_stopped(). Without the
> * memory barrier, there is a small possibility that
> tg3_start_xmit()
> * will miss it and cause the queue to be stopped forever.
> */
> smp_mb();
>
> if (unlikely(netif_tx_queue_stopped(txq) &&
> (tg3_tx_avail(tnapi) > TG3_TX_WAKEUP_THRESH(tnapi))))
> {
> __netif_tx_lock(txq, smp_processor_id());
> if (netif_tx_queue_stopped(txq) &&
> (tg3_tx_avail(tnapi) > TG3_TX_WAKEUP_THRESH(tnapi)))
> netif_tx_wake_queue(txq);
> __netif_tx_unlock(txq);
> }
>
> === tg3_start_xmit ===
> budget = tg3_tx_avail(tnapi);
>
> /* We are running in BH disabled context with netif_tx_lock
> * and TX reclaim runs via tp->napi.poll inside of a software
> * interrupt. Furthermore, IRQ processing runs lockless so we have
> * no IRQ context deadlocks to worry about either. Rejoice!
> */
> if (unlikely(budget <= (skb_shinfo(skb)->nr_frags + 1))) {
> if (!netif_tx_queue_stopped(txq)) {
> netif_tx_stop_queue(txq);
>
> /* This is a hard error, log it. */
> netdev_err(dev,
> "BUG! Tx Ring full when queue
> awake!\n");
> }
> return NETDEV_TX_BUSY;
> }
>
>
> 2015-06-05 16:40 GMT+08:00 Felix Fietkau <n...@openwrt.org>:
>
>> On 2015-06-02 15:06, michael lee wrote:
>> > use pktgen to verify on rt3662. can improve transmit rate.
>> > pkt_size 1500
>> > burst 1 : 807Mb/sec
>> > burst 8 : 984Mb/sec
>> >
>> > pkt_size 60
>> > burst 1 : 57Mb/sec
>> > burst 8 : 236Mb/sec
>> >
>> > Signed-off-by: michael lee <igv...@gmail.com>
>> > ---
>> > .../drivers/net/ethernet/ralink/ralink_soc_eth.c | 51
>> +++++++++++++---------
>> > .../drivers/net/ethernet/ralink/ralink_soc_eth.h | 2 +
>> > 2 files changed, 33 insertions(+), 20 deletions(-)
>> >
>> > diff --git
>> a/target/linux/ramips/files/drivers/net/ethernet/ralink/ralink_soc_eth.c
>> b/target/linux/ramips/files/drivers/net/ethernet/ralink/ralink_soc_eth.c
>> > index b2304bb..4b39825 100644
>> > ---
>> a/target/linux/ramips/files/drivers/net/ethernet/ralink/ralink_soc_eth.c
>> > +++
>> b/target/linux/ramips/files/drivers/net/ethernet/ralink/ralink_soc_eth.c
>> > @@ -337,6 +337,8 @@ static int fe_alloc_tx(struct fe_priv *priv)
>> > struct fe_tx_ring *ring = &priv->tx_ring;
>> >
>> > ring->tx_free_idx = 0;
>> > + ring->tx_next_idx = 0;
>> > + ring->tx_thresh = max((unsigned long)ring->tx_ring_size >> 2,
>> MAX_SKB_FRAGS);
>> >
>> > ring->tx_buf = kcalloc(ring->tx_ring_size, sizeof(*ring->tx_buf),
>> > GFP_KERNEL);
>> > @@ -525,8 +527,16 @@ static int fe_vlan_rx_kill_vid(struct net_device
>> *dev,
>> > return 0;
>> > }
>> >
>> > +static inline u32 fe_empty_txd(struct fe_tx_ring *ring)
>> > +{
>> > + barrier();
>> What is this barrier for?
>>
>> > + return (u32)(ring->tx_ring_size -
>> > + ((ring->tx_next_idx - ring->tx_free_idx) &
>> > + (ring->tx_ring_size - 1)));
>> > +}
>> > +
>> > static int fe_tx_map_dma(struct sk_buff *skb, struct net_device *dev,
>> > - int idx, int tx_num, struct fe_tx_ring *ring)
>> > + int tx_num, struct fe_tx_ring *ring)
>> > {
>> > struct fe_priv *priv = netdev_priv(dev);
>> > struct skb_frag_struct *frag;
>> > @@ -649,14 +659,22 @@ static int fe_tx_map_dma(struct sk_buff *skb,
>> struct net_device *dev,
>> > netdev_sent_queue(dev, skb->len);
>> > skb_tx_timestamp(skb);
>> >
>> > - j = NEXT_TX_DESP_IDX(j);
>> > + ring->tx_next_idx = NEXT_TX_DESP_IDX(j);
>> > wmb();
>> > - fe_reg_w32(j, FE_REG_TX_CTX_IDX0);
>> > + if (unlikely(fe_empty_txd(ring) <= ring->tx_thresh)) {
>> > + netif_stop_queue(dev);
>> > + smp_mb();
>> > + if (unlikely(fe_empty_txd(ring) > ring->tx_thresh))
>> > + netif_wake_queue(dev);
>> Why do that queue wake check here, when it's already being done during
>> tx cleanup.
>>
>> > + }
>> > +
>> > + if (netif_xmit_stopped(netdev_get_tx_queue(dev, 0)) ||
>> !skb->xmit_more)
>> > + fe_reg_w32(ring->tx_next_idx, FE_REG_TX_CTX_IDX0);
>> >
>> > return 0;
>> >
>> > err_dma:
>> > - j = idx;
>> > + j = ring->tx_next_idx;
>> > for (i = 0; i < tx_num; i++) {
>> > ptxd = &ring->tx_dma[j];
>> > tx_buf = &ring->tx_buf[j];
>>
>> - Felix
>>
>
>
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