RE: [PATCH 1/2 v2] mv643xx_eth: use sw csum for big packets

From: Saeed Bishara
Date: Thu Jun 10 2010 - 03:38:06 EST




>-----Original Message-----
>From: Lennert Buytenhek [mailto:buytenh@xxxxxxxxxxxxxx]
>Sent: Thursday, June 10, 2010 9:44 AM
>To: Saeed Bishara
>Cc: linux-net@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>Subject: Re: [PATCH 1/2 v2] mv643xx_eth: use sw csum for big packets
>
>On Wed, Jun 09, 2010 at 11:51:23AM +0300, Saeed Bishara wrote:
>
>> diff --git a/drivers/net/mv643xx_eth.c b/drivers/net/mv643xx_eth.c
>> index e345ec8..2d0e06b 100644
>> --- a/drivers/net/mv643xx_eth.c
>> +++ b/drivers/net/mv643xx_eth.c
>> @@ -289,6 +289,7 @@ struct mv643xx_eth_shared_private {
>> unsigned int t_clk;
>> int extended_rx_coal_limit;
>> int tx_bw_control;
>> + int tx_csum_limit;
>> };
>>
>> #define TX_BW_CONTROL_ABSENT 0
>> @@ -782,7 +783,8 @@ static int txq_submit_skb(struct
>tx_queue *txq, struct sk_buff *skb)
>> skb->protocol != htons(ETH_P_8021Q));
>>
>> tag_bytes = (void *)ip_hdr(skb) - (void
>*)skb->data - ETH_HLEN;
>> - if (unlikely(tag_bytes & ~12)) {
>> + if (unlikely(tag_bytes & ~12) ||
>> + skb->len > mp->shared->tx_csum_limit) {
>
>Please line up skb->len with unlikely() on the line above it.
>
>
>> @@ -2666,6 +2668,9 @@ static int
>mv643xx_eth_shared_probe(struct platform_device *pdev)
>> * Detect hardware parameters.
>> */
>> msp->t_clk = (pd != NULL && pd->t_clk != 0) ? pd->t_clk
>: 133000000;
>> + msp->tx_csum_limit = pd->tx_csum_limit ?
>pd->tx_csum_limit : 9 * 1024;
>> + /* add header count so we can compare against skb->len */
>> + msp->tx_csum_limit += ETH_HLEN;
>> infer_hw_params(msp);
>
>Is the limit 9 * 1024 + 14 for the whole packet, or 9 * 1024 for the IP
>part?
the limit is for the IP part, but I thought that adding the header length, then comparing agains skb->len will be the same. What do you suggest?

>
>I.e. what happens if skb->len is 9 * 1024 + 15, but there is one VLAN
>tag present -- will the hardware be able to do the checksum offload or
>not?
>--
To unsubscribe from this list: send the line "unsubscribe linux-net" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html