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Message-ID: <CANEJEGtndncj1biMZSBC1rt36a66iWGp7wU_OxCxpA_PVBGZqA@mail.gmail.com>
Date: Wed, 14 Mar 2012 23:42:00 -0700
From: Grant Grundler <grundler@...omium.org>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
David Miller <davem@...emloft.net>, linux-usb@...r.kernel.org,
netdev <netdev@...r.kernel.org>,
Aurelien Jacobs <aurel@...age.org>,
Trond Wuellner <trond@...omium.org>,
Paul Stewart <pstew@...omium.org>,
Allan Chou <allan@...x.com.tw>
Subject: Re: [PATCH net-next] asix: asix_rx_fixup surgery to reduce skb truesizes
Adding ASIX (Allan Chou)
On Wed, Mar 14, 2012 at 11:18 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> 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)
Your rewrite is definitely cleaner/simpler. If it works, ship it! :)
I'm traveling right now and don't have access to the HW to test it.
I'm hoping that ASIX could run a few simple tests as well.
> 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@...il.com>
> Cc: Aurelien Jacobs <aurel@...age.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Trond Wuellner <trond@...omium.org>
> Cc: Grant Grundler <grundler@...omium.org>
Reviewed-by: Grant Grundler <grundler@...omium.org>
thanks!
grant
> Cc: Paul Stewart <pstew@...omium.org>
> ---
> drivers/net/usb/asix.c | 90 +++++++++------------------------------
> 1 file changed, 21 insertions(+), 69 deletions(-)
>
> diff --git a/drivers/net/usb/asix.c b/drivers/net/usb/asix.c
> index 8e84f5b..27d5440 100644
> --- a/drivers/net/usb/asix.c
> +++ b/drivers/net/usb/asix.c
> @@ -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);
> -
> - 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");
> + while (offset + sizeof(u32) < skb->len) {
> + struct sk_buff *ax_skb;
> + u16 size;
> + u32 header = get_unaligned_le32(skb->data + offset);
>
> + 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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