Commit a9e0aca4 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

asix: asix_rx_fixup surgery to reduce skb truesizes 



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: default avatarEric 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: default avatarGrant Grundler <grundler@chromium.org>
Reviewed-by: default avatarGrant Grundler <grundler@chromium.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1174764e

drivers/net/usb/asix.c

+20 −68
Original line number Diff line number Diff line
@@ -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;

	int offset = 0;



	while (offset + sizeof(u32) < skb->len) {

		struct sk_buff *ax_skb;

		u16 size;

		u32 header = get_unaligned_le32(skb->data + offset);



	head = (u8 *) skb->data;

	memcpy(&header, head, sizeof(header));

	le32_to_cpus(&header);

	packet = head + sizeof(header);



	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);



		if (skb->len < sizeof(header))

			break;

		skb_put(ax_skb, size);

		memcpy(ax_skb->data, skb->data + offset, size);

		usbnet_skb_return(dev, ax_skb);



		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,

};

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