Subject: Re: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.

From: Eric Dumazet <[email-masked]>
Date: Wed, 25 Mar 2009 15:04:26 +0100

Joakim Tjernlund a écrit :
>>>From 1c2f23b1f37f4818c0fd0217b93eb38ab6564840 Mon Sep 17 00:00:00 2001
> From: Joakim Tjernlund <[email-masked]>
> Date: Tue, 24 Mar 2009 10:19:27 +0100
> Subject: [PATCH] ucc_geth: Move freeing of TX packets to NAPI context.
>  Also increase NAPI weight somewhat.
>  This will make the system alot more responsive while
>  ping flooding the ucc_geth ethernet interaface.
> 
> 
> Signed-off-by: Joakim Tjernlund <[email-masked]>
> ---
>  drivers/net/ucc_geth.c |   30 +++++++++++-------------------
>  drivers/net/ucc_geth.h |    2 +-
>  2 files changed, 12 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/net/ucc_geth.c b/drivers/net/ucc_geth.c
> index 097aed8..7d5d110 100644
> --- a/drivers/net/ucc_geth.c
> +++ b/drivers/net/ucc_geth.c
> @@ -3214,7 +3214,7 @@ static int ucc_geth_tx(struct net_device *dev, u8 txQ)
>  		dev->stats.tx_packets++;
>  
>  		/* Free the sk buffer associated with this TxBD */
> -		dev_kfree_skb_irq(ugeth->
> +		dev_kfree_skb(ugeth->
>  				  tx_skbuff[txQ][ugeth->skb_dirtytx[txQ]]);
>  		ugeth->tx_skbuff[txQ][ugeth->skb_dirtytx[txQ]] = NULL;
>  		ugeth->skb_dirtytx[txQ] =
> @@ -3248,9 +3248,16 @@ static int ucc_geth_poll(struct napi_struct *napi, int budget)
>  	for (i = 0; i < ug_info->numQueuesRx; i++)
>  		howmany += ucc_geth_rx(ugeth, i, budget - howmany);
>  

Cant you test (ucce & UCCE_TX_EVENTS) or something here to avoid
taking lock and checking queues if not necessary ?

> +	/* Tx event processing */
> +	spin_lock(&ugeth->lock);
> +	for (i = 0; i < ug_info->numQueuesTx; i++) {
> +		ucc_geth_tx(ugeth->dev, i);
> +	}
> +	spin_unlock(&ugeth->lock);
> +

Why tx completions dont change "howmany" ?
It seems strange you changed UCC_GETH_DEV_WEIGHT if not taking into account tx event above...

>  	if (howmany < budget) {
>  		netif_rx_complete(napi);
> -		setbits32(ugeth->uccf->p_uccm, UCCE_RX_EVENTS);
> +		setbits32(ugeth->uccf->p_uccm, UCCE_RX_EVENTS | UCCE_TX_EVENTS);
>  	}
>  
>  	return howmany;
> @@ -3264,8 +3271,6 @@ static irqreturn_t ucc_geth_irq_handler(int irq, void *info)
>  	struct ucc_geth_info *ug_info;
>  	register u32 ucce;
>  	register u32 uccm;
> -	register u32 tx_mask;
> -	u8 i;
>  
>  	ugeth_vdbg("%s: IN", __func__);
>  
> @@ -3279,27 +3284,14 @@ static irqreturn_t ucc_geth_irq_handler(int irq, void *info)
>  	out_be32(uccf->p_ucce, ucce);
>  
>  	/* check for receive events that require processing */
> -	if (ucce & UCCE_RX_EVENTS) {
> +	if (ucce & (UCCE_RX_EVENTS | UCCE_TX_EVENTS)) {
>  		if (netif_rx_schedule_prep(&ugeth->napi)) {
> -			uccm &= ~UCCE_RX_EVENTS;
> +			uccm &= ~(UCCE_RX_EVENTS | UCCE_TX_EVENTS);
>  			out_be32(uccf->p_uccm, uccm);
>  			__netif_rx_schedule(&ugeth->napi);
>  		}
>  	}
>  
> -	/* Tx event processing */
> -	if (ucce & UCCE_TX_EVENTS) {
> -		spin_lock(&ugeth->lock);
> -		tx_mask = UCC_GETH_UCCE_TXB0;
> -		for (i = 0; i < ug_info->numQueuesTx; i++) {
> -			if (ucce & tx_mask)
> -				ucc_geth_tx(dev, i);
> -			ucce &= ~tx_mask;
> -			tx_mask <<= 1;
> -		}
> -		spin_unlock(&ugeth->lock);
> -	}
> -
>  	/* Errors and other events */
>  	if (ucce & UCCE_OTHER) {
>  		if (ucce & UCC_GETH_UCCE_BSY)
> diff --git a/drivers/net/ucc_geth.h b/drivers/net/ucc_geth.h
> index 44218b8..ea30aa7 100644
> --- a/drivers/net/ucc_geth.h
> +++ b/drivers/net/ucc_geth.h
> @@ -843,7 +843,7 @@ struct ucc_geth_hardware_statistics {
>  /* Driver definitions */
>  #define TX_BD_RING_LEN                          0x10
>  #define RX_BD_RING_LEN                          0x10
> -#define UCC_GETH_DEV_WEIGHT                     TX_BD_RING_LEN
> +#define UCC_GETH_DEV_WEIGHT                     (RX_BD_RING_LEN+TX_BD_RING_LEN/2)
>  
>  #define TX_RING_MOD_MASK(size)                  (size-1)
>  #define RX_RING_MOD_MASK(size)                  (size-1)