iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

asix: asix_rx_fixup surgery to reduce skb truesizes

Browse Source 
asix_rx_fixup() is complex, and does some unnecessary memory copies (at
least on x86 where NET_IP_ALIGN is 0)

Also, it tends to provide skbs with a big truesize (4096+256 with
MTU=1500) to upper stack, so incoming trafic consume a lot of memory and
I noticed early packet drops because we hit socket rcvbuf too fast.

Switch to a different strategy, using copybreak so that we provide nice
skbs to upper stack (including the NET_SKB_PAD to avoid future head
reallocations in some paths)

With this patch, I no longer see packets drops or tcp collapses on
various tcp workload with a AX88772 adapter.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Aurelien Jacobs <aurel@gnuage.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Trond Wuellner <trond@chromium.org>
Cc: Grant Grundler <grundler@chromium.org>
Cc: Paul Stewart <pstew@chromium.org>
Reviewed-by: Grant Grundler <grundler@chromium.org>
Reviewed-by: Grant Grundler <grundler@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-03-14 20:18:32 +00:00 committed by David S. Miller
parent 1174764e81
commit a9e0aca4b3
1 changed files with 20 additions and 68 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

88
drivers/net/usb/asix.c
View File

@ -305,88 +305,40 @@ asix_write_cmd_async(struct usbnet *dev, u8 cmd, u16 value, u16 index,
static int asix_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
{
u8 *head;
u32 header;
char *packet;
struct sk_buff *ax_skb;
u16 size;
int offset = 0;
head = (u8 *) skb->data;
memcpy(&header, head, sizeof(header));
le32_to_cpus(&header);
packet = head + sizeof(header);
while (offset + sizeof(u32) < skb->len) {
struct sk_buff *ax_skb;
u16 size;
u32 header = get_unaligned_le32(skb->data + offset);
skb_pull(skb, 4);
while (skb->len > 0) {
if ((header & 0x07ff) != ((~header >> 16) & 0x07ff))
netdev_err(dev->net, "asix_rx_fixup() Bad Header Length\n");
offset += sizeof(u32);
/* get the packet length */
size = (u16) (header & 0x000007ff);
if ((skb->len) - ((size + 1) & 0xfffe) == 0) {
u8 alignment = (unsigned long)skb->data & 0x3;
if (alignment != 0x2) {
/*
* not 16bit aligned so use the room provided by
* the 32 bit header to align the data
*
* note we want 16bit alignment as MAC header is
* 14bytes thus ip header will be aligned on
* 32bit boundary so accessing ipheader elements
* using a cast to struct ip header wont cause
* an unaligned accesses.
*/
u8 realignment = (alignment + 2) & 0x3;
memmove(skb->data - realignment,
skb->data,
size);
skb->data -= realignment;
skb_set_tail_pointer(skb, size);
}
return 2;
size = (u16) (header & 0x7ff);
if (size != ((~header >> 16) & 0x07ff)) {
netdev_err(dev->net, "asix_rx_fixup() Bad Header Length\n");
return 0;
}
if (size > dev->net->mtu + ETH_HLEN) {
if ((size > dev->net->mtu + ETH_HLEN) ||
(size + offset > skb->len)) {
netdev_err(dev->net, "asix_rx_fixup() Bad RX Length %d\n",
size);
return 0;
}
ax_skb = skb_clone(skb, GFP_ATOMIC);
if (ax_skb) {
u8 alignment = (unsigned long)packet & 0x3;
ax_skb->len = size;
if (alignment != 0x2) {
/*
* not 16bit aligned use the room provided by
* the 32 bit header to align the data
*/
u8 realignment = (alignment + 2) & 0x3;
memmove(packet - realignment, packet, size);
packet -= realignment;
}
ax_skb->data = packet;
skb_set_tail_pointer(ax_skb, size);
usbnet_skb_return(dev, ax_skb);
} else {
ax_skb = netdev_alloc_skb_ip_align(dev->net, size);
if (!ax_skb)
return 0;
}
skb_pull(skb, (size + 1) & 0xfffe);
skb_put(ax_skb, size);
memcpy(ax_skb->data, skb->data + offset, size);
usbnet_skb_return(dev, ax_skb);
if (skb->len < sizeof(header))
break;
head = (u8 *) skb->data;
memcpy(&header, head, sizeof(header));
le32_to_cpus(&header);
packet = head + sizeof(header);
skb_pull(skb, 4);
offset += (size + 1) & 0xfffe;
}
if (skb->len < 0) {
if (skb->len != offset) {
netdev_err(dev->net, "asix_rx_fixup() Bad SKB Length %d\n",
skb->len);
return 0;
@ -1541,7 +1493,7 @@ static const struct driver_info ax88772_info = {
.status = asix_status,
.link_reset = ax88772_link_reset,
.reset = ax88772_reset,
.flags = FLAG_ETHER | FLAG_FRAMING_AX | FLAG_LINK_INTR,
.flags = FLAG_ETHER | FLAG_FRAMING_AX | FLAG_LINK_INTR | FLAG_MULTI_PACKET,
.rx_fixup = asix_rx_fixup,
.tx_fixup = asix_tx_fixup,
};