[ofa-general] Re: [PATCH 10/10 Rev4] [E1000] Implement batching

["Kok, Auke" <auke-jan.h.kok@intel.com>]

Krishna Kumar wrote:
> E1000: Implement batching capability (ported thanks to changes taken from
> 	Jamal). Not all changes are made in this as in IPoIB, eg, handling
> 	out of order skbs (see XXX in the first mail).
> 
> Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
> ---
>  e1000_main.c |  150 +++++++++++++++++++++++++++++++++++++++++++++++------------
>  1 files changed, 121 insertions(+), 29 deletions(-)


Krishna,

while I appreciate the patch I would have preferred a patch to e1000e. Not only 
does the e1000e driver remove a lot of the workarounds for old silicon, it is 
also a good way for us to move the current e1000 driver into a bit more stable 
maintenance mode.

Do you think you can write this patch for e1000e instead? code-wise a lot of 
things are still the same, so your patch should be relatively easy to generate.

e1000e currently lives in a branch from jeff garzik's netdev-2.6 tree

Thanks,

Auke

> 
> diff -ruNp org/drivers/net/e1000/e1000_main.c new/drivers/net/e1000/e1000_main.c
> --- org/drivers/net/e1000/e1000_main.c	2007-08-20 14:26:29.000000000 +0530
> +++ new/drivers/net/e1000/e1000_main.c	2007-08-22 08:33:51.000000000 +0530
> @@ -157,6 +157,7 @@ static void e1000_update_phy_info(unsign
>  static void e1000_watchdog(unsigned long data);
>  static void e1000_82547_tx_fifo_stall(unsigned long data);
>  static int e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev);
> +static int e1000_xmit_frames(struct net_device *dev);
>  static struct net_device_stats * e1000_get_stats(struct net_device *netdev);
>  static int e1000_change_mtu(struct net_device *netdev, int new_mtu);
>  static int e1000_set_mac(struct net_device *netdev, void *p);
> @@ -990,7 +991,7 @@ e1000_probe(struct pci_dev *pdev,
>  	if (pci_using_dac)
>  		netdev->features |= NETIF_F_HIGHDMA;
>  
> -	netdev->features |= NETIF_F_LLTX;
> +	netdev->features |= NETIF_F_LLTX | NETIF_F_BATCH_SKBS;
>  
>  	adapter->en_mng_pt = e1000_enable_mng_pass_thru(&adapter->hw);
>  
> @@ -3098,6 +3099,18 @@ e1000_tx_map(struct e1000_adapter *adapt
>  	return count;
>  }
>  
> +static void e1000_kick_DMA(struct e1000_adapter *adapter,
> +			   struct e1000_tx_ring *tx_ring, int i)
> +{
> +	wmb();
> +
> +	writel(i, adapter->hw.hw_addr + tx_ring->tdt);
> +	/* we need this if more than one processor can write to our tail
> +	 * at a time, it syncronizes IO on IA64/Altix systems */
> +	mmiowb();
> +}
> +
> +
>  static void
>  e1000_tx_queue(struct e1000_adapter *adapter, struct e1000_tx_ring *tx_ring,
>                 int tx_flags, int count)
> @@ -3144,13 +3157,7 @@ e1000_tx_queue(struct e1000_adapter *ada
>  	 * know there are new descriptors to fetch.  (Only
>  	 * applicable for weak-ordered memory model archs,
>  	 * such as IA-64). */
> -	wmb();
> -
>  	tx_ring->next_to_use = i;
> -	writel(i, adapter->hw.hw_addr + tx_ring->tdt);
> -	/* we need this if more than one processor can write to our tail
> -	 * at a time, it syncronizes IO on IA64/Altix systems */
> -	mmiowb();
>  }
>  
>  /**
> @@ -3257,21 +3264,31 @@ static int e1000_maybe_stop_tx(struct ne
>  }
>  
>  #define TXD_USE_COUNT(S, X) (((S) >> (X)) + 1 )
> +
> +struct e1000_tx_cbdata {
> +	int count;
> +	unsigned int max_per_txd;
> +	unsigned int nr_frags;
> +	unsigned int mss;
> +};
> +
> +#define E1000_SKB_CB(__skb)	((struct e1000_tx_cbdata *)&((__skb)->cb[0]))
> +#define NETDEV_TX_DROPPED	-5
> +
>  static int
> -e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
> +e1000_prep_queue_frame(struct sk_buff *skb, struct net_device *netdev)
>  {
>  	struct e1000_adapter *adapter = netdev_priv(netdev);
>  	struct e1000_tx_ring *tx_ring;
> -	unsigned int first, max_per_txd = E1000_MAX_DATA_PER_TXD;
> +	unsigned int max_per_txd = E1000_MAX_DATA_PER_TXD;
>  	unsigned int max_txd_pwr = E1000_MAX_TXD_PWR;
> -	unsigned int tx_flags = 0;
>  	unsigned int len = skb->len;
> -	unsigned long flags;
> -	unsigned int nr_frags = 0;
> -	unsigned int mss = 0;
> +	unsigned int nr_frags;
> +	unsigned int mss;
>  	int count = 0;
> -	int tso;
>  	unsigned int f;
> +	struct e1000_tx_cbdata *cb = E1000_SKB_CB(skb);
> +
>  	len -= skb->data_len;
>  
>  	/* This goes back to the question of how to logically map a tx queue
> @@ -3282,7 +3299,7 @@ e1000_xmit_frame(struct sk_buff *skb, st
>  
>  	if (unlikely(skb->len <= 0)) {
>  		dev_kfree_skb_any(skb);
> -		return NETDEV_TX_OK;
> +		return NETDEV_TX_DROPPED;
>  	}
>  
>  	/* 82571 and newer doesn't need the workaround that limited descriptor
> @@ -3328,7 +3345,7 @@ e1000_xmit_frame(struct sk_buff *skb, st
>  					DPRINTK(DRV, ERR,
>  						"__pskb_pull_tail failed.\n");
>  					dev_kfree_skb_any(skb);
> -					return NETDEV_TX_OK;
> +					return NETDEV_TX_DROPPED;
>  				}
>  				len = skb->len - skb->data_len;
>  				break;
> @@ -3372,22 +3389,32 @@ e1000_xmit_frame(struct sk_buff *skb, st
>  	    (adapter->hw.mac_type == e1000_82573))
>  		e1000_transfer_dhcp_info(adapter, skb);
>  
> -	if (!spin_trylock_irqsave(&tx_ring->tx_lock, flags))
> -		/* Collision - tell upper layer to requeue */
> -		return NETDEV_TX_LOCKED;
> +	cb->count = count;
> +	cb->max_per_txd = max_per_txd;
> +	cb->nr_frags = nr_frags;
> +	cb->mss = mss;
> +
> +	return NETDEV_TX_OK;
> +}
> +
> +static int e1000_queue_frame(struct sk_buff *skb, struct net_device *netdev)
> +{
> +	struct e1000_adapter *adapter = netdev_priv(netdev);
> +	struct e1000_tx_ring *tx_ring = adapter->tx_ring;
> +	int tso;
> +	unsigned int first;
> +	unsigned int tx_flags = 0;
> +	struct e1000_tx_cbdata *cb = E1000_SKB_CB(skb);
>  
>  	/* need: count + 2 desc gap to keep tail from touching
>  	 * head, otherwise try next time */
> -	if (unlikely(e1000_maybe_stop_tx(netdev, tx_ring, count + 2))) {
> -		spin_unlock_irqrestore(&tx_ring->tx_lock, flags);
> +	if (unlikely(e1000_maybe_stop_tx(netdev, tx_ring, cb->count + 2)))
>  		return NETDEV_TX_BUSY;
> -	}
>  
>  	if (unlikely(adapter->hw.mac_type == e1000_82547)) {
>  		if (unlikely(e1000_82547_fifo_workaround(adapter, skb))) {
>  			netif_stop_queue(netdev);
>  			mod_timer(&adapter->tx_fifo_stall_timer, jiffies + 1);
> -			spin_unlock_irqrestore(&tx_ring->tx_lock, flags);
>  			return NETDEV_TX_BUSY;
>  		}
>  	}
> @@ -3402,8 +3429,7 @@ e1000_xmit_frame(struct sk_buff *skb, st
>  	tso = e1000_tso(adapter, tx_ring, skb);
>  	if (tso < 0) {
>  		dev_kfree_skb_any(skb);
> -		spin_unlock_irqrestore(&tx_ring->tx_lock, flags);
> -		return NETDEV_TX_OK;
> +		return NETDEV_TX_DROPPED;
>  	}
>  
>  	if (likely(tso)) {
> @@ -3420,12 +3446,78 @@ e1000_xmit_frame(struct sk_buff *skb, st
>  
>  	e1000_tx_queue(adapter, tx_ring, tx_flags,
>  	               e1000_tx_map(adapter, tx_ring, skb, first,
> -	                            max_per_txd, nr_frags, mss));
> +	                            cb->max_per_txd, cb->nr_frags, cb->mss));
> +
> +	return NETDEV_TX_OK;
> +}
>  
> -	netdev->trans_start = jiffies;
> +static inline int e1000_xmit_frames(struct net_device *netdev)
> +{
> +	struct e1000_adapter *adapter = netdev->priv;
> +	struct e1000_tx_ring *tx_ring = adapter->tx_ring;
> +	int ret = NETDEV_TX_OK;
> +	int skbs_done = 0;
> +	struct sk_buff *skb;
> +	unsigned long flags;
> +
> +	if (!spin_trylock_irqsave(&tx_ring->tx_lock, flags)) {
> +		/* Collision - tell upper layer to requeue */
> +		return NETDEV_TX_LOCKED;
> +	}
>  
> -	/* Make sure there is space in the ring for the next send. */
> -	e1000_maybe_stop_tx(netdev, tx_ring, MAX_SKB_FRAGS + 2);
> +	while ((skb = __skb_dequeue(netdev->skb_blist)) != NULL) {
> +		if ((ret = e1000_prep_queue_frame(skb, netdev)) != NETDEV_TX_OK)
> +			continue;
> +
> +		ret = e1000_queue_frame(skb, netdev);
> +		if (ret == NETDEV_TX_OK) {
> +			skbs_done++;
> +		} else {
> +			if (ret == NETDEV_TX_BUSY)
> +				__skb_queue_head(netdev->skb_blist, skb);
> +			break;
> +		}
> +	}
> +
> +	if (skbs_done) {
> +		e1000_kick_DMA(adapter, tx_ring, adapter->tx_ring->next_to_use);
> +		netdev->trans_start = jiffies;
> +		e1000_maybe_stop_tx(netdev, tx_ring, MAX_SKB_FRAGS + 2);
> +	}
> +
> +	spin_unlock_irqrestore(&tx_ring->tx_lock, flags);
> +
> +	if (ret == NETDEV_TX_DROPPED)
> +		ret = NETDEV_TX_OK;
> +
> +	return ret;
> +}
> +
> +static int e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
> +{
> +	struct e1000_adapter *adapter = netdev_priv(netdev);
> +	struct e1000_tx_ring *tx_ring = adapter->tx_ring;
> +	unsigned long flags;
> +
> +	if (!skb)
> +		return e1000_xmit_frames(netdev);
> +
> +	if (!spin_trylock_irqsave(&tx_ring->tx_lock, flags)) {
> +		/* Collision - tell upper layer to requeue */
> +		return NETDEV_TX_LOCKED;
> +	}
> +
> +	if (unlikely(e1000_prep_queue_frame(skb, netdev) != NETDEV_TX_OK)) {
> +		spin_unlock_irqrestore(&tx_ring->tx_lock, flags);
> +		return NETDEV_TX_OK;
> +	}
> +
> +	if (e1000_queue_frame(skb, netdev) == NETDEV_TX_OK) {
> +		e1000_kick_DMA(adapter, tx_ring, adapter->tx_ring->next_to_use);
> +		netdev->trans_start = jiffies;
> +		/* Make sure there is space in the ring for the next send. */
> +		e1000_maybe_stop_tx(netdev, tx_ring, MAX_SKB_FRAGS + 2);
> +	}
>  
>  	spin_unlock_irqrestore(&tx_ring->tx_lock, flags);
>  	return NETDEV_TX_OK;
> -
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