2007-08-11 06:32:41

by Divy Le ray

Subject: [PATCH 4/13] cxgb3 - use immediate data for offload Tx

From: Divy Le Ray <[email protected]>

Send small TX_DATA work requests as immediate data even when
there are fragments.

Signed-off-by: Divy Le Ray <[email protected]>
---

drivers/net/cxgb3/sge.c | 17 +++++++++++------
1 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/net/cxgb3/sge.c b/drivers/net/cxgb3/sge.c
index 9213cda..dca2716 100644
--- a/drivers/net/cxgb3/sge.c
+++ b/drivers/net/cxgb3/sge.c
@@ -1182,8 +1182,8 @@ int t3_eth_xmit(struct sk_buff *skb, struct net_device *dev)
*
* Writes a packet as immediate data into a Tx descriptor. The packet
* contains a work request at its beginning. We must write the packet
- * carefully so the SGE doesn't read accidentally before it's written in
- * its entirety.
+ * carefully so the SGE doesn't read it accidentally before it's written
+ * in its entirety.
*/
static inline void write_imm(struct tx_desc *d, struct sk_buff *skb,
unsigned int len, unsigned int gen)
@@ -1191,7 +1191,11 @@ static inline void write_imm(struct tx_desc *d, struct sk_buff *skb,
struct work_request_hdr *from = (struct work_request_hdr *)skb->data;
struct work_request_hdr *to = (struct work_request_hdr *)d;

- memcpy(&to[1], &from[1], len - sizeof(*from));
+ if (likely(!skb->data_len))
+ memcpy(&to[1], &from[1], len - sizeof(*from));
+ else
+ skb_copy_bits(skb, sizeof(*from), &to[1], len - sizeof(*from));
+
to->wr_hi = from->wr_hi | htonl(F_WR_SOP | F_WR_EOP |
V_WR_BCNTLFLT(len & 7));
wmb();
@@ -1261,7 +1265,7 @@ static inline void reclaim_completed_tx_imm(struct sge_txq *q)

static inline int immediate(const struct sk_buff *skb)
{
- return skb->len <= WR_LEN && !skb->data_len;
+ return skb->len <= WR_LEN;
}

/**
@@ -1467,12 +1471,13 @@ static void write_ofld_wr(struct adapter *adap, struct sk_buff *skb,
*/
static inline unsigned int calc_tx_descs_ofld(const struct sk_buff *skb)
{
- unsigned int flits, cnt = skb_shinfo(skb)->nr_frags;
+ unsigned int flits, cnt;

- if (skb->len <= WR_LEN && cnt == 0)
+ if (skb->len <= WR_LEN)
return 1; /* packet fits as immediate data */

flits = skb_transport_offset(skb) / 8; /* headers */
+ cnt = skb_shinfo(skb)->nr_frags;
if (skb->tail != skb->transport_header)
cnt++;
return flits_to_desc(flits + sgl_len(cnt));

2007-08-14 05:46:01

by Jeff Garzik

Subject: Re: [PATCH 4/13] cxgb3 - use immediate data for offload Tx

Divy Le Ray wrote:
> From: Divy Le Ray <[email protected]>
>
> Send small TX_DATA work requests as immediate data even when
> there are fragments.
>
> Signed-off-by: Divy Le Ray <[email protected]>
> ---
>
> drivers/net/cxgb3/sge.c | 17 +++++++++++------
> 1 files changed, 11 insertions(+), 6 deletions(-)

needs additional explanation. don't just describe the new post-change
behavior, describe why this change is needed.

2007-08-14 23:26:04

by Divy Le ray

Subject: Re: [PATCH 4/13] cxgb3 - use immediate data for offload Tx

Jeff Garzik wrote:
>
> Divy Le Ray wrote:
> > From: Divy Le Ray <[email protected]>
> >
> > Send small TX_DATA work requests as immediate data even when
> > there are fragments.
> >
> > Signed-off-by: Divy Le Ray <[email protected]>
> > ---
> >
> > drivers/net/cxgb3/sge.c | 17 +++++++++++------
> > 1 files changed, 11 insertions(+), 6 deletions(-)
>
> needs additional explanation. don't just describe the new post-change
> behavior, describe why this change is needed.
>
>
It's an optimization avoiding doing multiple DMAs for small fragmented
packets.
The driver already implements this optimization for small contiguous
packets.

Divy