On Wed, 2013-07-31 at 18:51 +0800, Ming Lei wrote: > This patch enables 'can_dma_sg' flag for ax88179_178a device > if the attached host controller supports building packet from > discontinuous buffers(DMA SG is possible), so both frame header > and skb data buffers can be passed to usb stack via urb->sg, > then skb data copy can be saved. > > With the patch, CPU utilization decreased much in iperf test at > client mode. > > Signed-off-by: Ming Lei <ming....@canonical.com> > --- > drivers/net/usb/ax88179_178a.c | 30 ++++++++++++++++++++++++++++++ > 1 file changed, 30 insertions(+) > > diff --git a/drivers/net/usb/ax88179_178a.c b/drivers/net/usb/ax88179_178a.c > index 5a468f3..c75bded 100644 > --- a/drivers/net/usb/ax88179_178a.c > +++ b/drivers/net/usb/ax88179_178a.c > @@ -1031,12 +1031,20 @@ static int ax88179_bind(struct usbnet *dev, struct > usb_interface *intf) > dev->mii.phy_id = 0x03; > dev->mii.supports_gmii = 1; > > + if (dev->udev->bus->no_sg_limit) > + dev->can_dma_sg = 1; > + > dev->net->features |= NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM | > NETIF_F_RXCSUM; > > dev->net->hw_features |= NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM | > NETIF_F_RXCSUM; > > + if (dev->can_dma_sg) { > + dev->net->features |= NETIF_F_SG | NETIF_F_TSO; > + dev->net->hw_features |= NETIF_F_SG | NETIF_F_TSO; > + } > + > /* Enable checksum offload */ > *tmp = AX_RXCOE_IP | AX_RXCOE_TCP | AX_RXCOE_UDP | > AX_RXCOE_TCPV6 | AX_RXCOE_UDPV6; > @@ -1170,12 +1178,30 @@ ax88179_tx_fixup(struct usbnet *dev, struct sk_buff > *skb, gfp_t flags) > int mss = skb_shinfo(skb)->gso_size; > int headroom; > int tailroom; > + struct skb_data *entry = (struct skb_data *)skb->cb; > > tx_hdr1 = skb->len; > tx_hdr2 = mss; > if (((skb->len + 8) % frame_size) == 0) > tx_hdr2 |= 0x80008000; /* Enable padding */ > > + if (dev->can_dma_sg) {
> + if (!(entry->header = kmalloc(8, GFP_ATOMIC))) > + goto no_sg; > + > + entry->length = 8; > + cpu_to_le32s(&tx_hdr1); > + cpu_to_le32s(&tx_hdr2); You could do these cpu_to_le32s() calls before the if (dev->can_dma_sg) and remove them before the skb_copy_to_linear_data() calls. > + memcpy(entry->header, &tx_hdr1, 4); > + memcpy(entry->header + 4, &tx_hdr2, 4); > + > + return skb; > + } else { > +no_sg: > + entry->header = NULL; > + entry->length = 0; > + } > + > headroom = skb_headroom(skb); > tailroom = skb_tailroom(skb); > > @@ -1323,6 +1349,10 @@ static int ax88179_reset(struct usbnet *dev) > > dev->net->hw_features |= NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM | > NETIF_F_RXCSUM; > + if (dev->can_dma_sg) { > + dev->net->features |= NETIF_F_SG | NETIF_F_TSO; > + dev->net->hw_features |= NETIF_F_SG | NETIF_F_TSO; > + } Are you sure this part is needed ? Also it looks like that you are going through this sg allocation/setup even for linear skb ? For linear skb, with 8+ bytes of headroom, I guess this adds significant overhead (2 kmalloc() + sg setup) -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html