>-----Original Message----- >From: Lennert Buytenhek [mailto:buytenh@xxxxxxxxxxxxxx] >Sent: Saturday, June 12, 2010 11:32 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 Thu, Jun 10, 2010 at 10:38:05AM +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? > >Right, but for the header length you take 14, while if to include VLAN >tags or DSA tags the header might actually be longer -- how does that >affect the ability of the hardware to compute the checksum? > >I.e. is the restriction "total packet length must be < N + 14 bytes" >or is it "the IP part must be < N bytes and it doesn't matter whether >there are VLAN tags or not"? It's the second option: "the IP part must be < N" regardless to the L2 header. saeed > >I.e.: > >> >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
