git.ipfire.org Git - thirdparty/openwrt.git/blob

   1 From e9048e2935f7d797c2ba047c15b705b57c2fa99a Mon Sep 17 00:00:00 2001
   2 From: Bitterblue Smith <rtl8821cerfe2@gmail.com>
   3 Date: Thu, 19 Dec 2024 00:33:20 +0200
   4 Subject: [PATCH] wifi: rtw88: usb: Copy instead of cloning the RX skb
   5
   6 "iperf3 -c 192.168.0.1 -R --udp -b 0" shows about 40% of datagrams
   7 are lost. Many torrents don't download faster than 3 MiB/s, probably
   8 because the Bittorrent protocol uses UDP. This is somehow related to
   9 the use of skb_clone() in the RX path.
  10
  11 Don't use skb_clone(). Instead allocate a new skb for each 802.11 frame
  12 received and copy the data from the big (32768 byte) skb.
  13
  14 With this patch, "iperf3 -c 192.168.0.1 -R --udp -b 0" shows only 1-2%
  15 of datagrams are lost, and torrents can reach download speeds of 36
  16 MiB/s.
  17
  18 Tested with RTL8812AU and RTL8822CU.
  19
  20 Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
  21 Acked-by: Ping-Ke Shih <pkshih@realtek.com>
  22 Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
  23 Link: https://patch.msgid.link/8c9d4f9d-ebd8-4dc0-a0c4-9ebe430521dd@gmail.com
  24 ---
  25  drivers/net/wireless/realtek/rtw88/usb.c | 52 ++++++++++++++----------
  26  1 file changed, 31 insertions(+), 21 deletions(-)
  27
  28 --- a/drivers/net/wireless/realtek/rtw88/usb.c
  29 +++ b/drivers/net/wireless/realtek/rtw88/usb.c
  30 @@ -7,6 +7,7 @@
  31  #include <linux/mutex.h>
  32  #include "main.h"
  33  #include "debug.h"
  34 +#include "mac.h"
  35  #include "reg.h"
  36  #include "tx.h"
  37  #include "rx.h"
  38 @@ -547,49 +548,58 @@ static void rtw_usb_rx_handler(struct wo
  39  {
  40         struct rtw_usb *rtwusb = container_of(work, struct rtw_usb, rx_work);
  41         struct rtw_dev *rtwdev = rtwusb->rtwdev;
  42 -       const struct rtw_chip_info *chip = rtwdev->chip;
  43 -       u32 pkt_desc_sz = chip->rx_pkt_desc_sz;
  44         struct ieee80211_rx_status rx_status;
  45 -       u32 pkt_offset, next_pkt, urb_len;
  46         struct rtw_rx_pkt_stat pkt_stat;
  47 -       struct sk_buff *next_skb;
  48 +       struct sk_buff *rx_skb;
  49         struct sk_buff *skb;
  50 +       u32 pkt_desc_sz = rtwdev->chip->rx_pkt_desc_sz;
  51 +       u32 max_skb_len = pkt_desc_sz + PHY_STATUS_SIZE * 8 +
  52 +                         IEEE80211_MAX_MPDU_LEN_VHT_11454;
  53 +       u32 pkt_offset, next_pkt, skb_len;
  54         u8 *rx_desc;
  55         int limit;
  56
  57         for (limit = 0; limit < 200; limit++) {
  58 -               skb = skb_dequeue(&rtwusb->rx_queue);
  59 -               if (!skb)
  60 +               rx_skb = skb_dequeue(&rtwusb->rx_queue);
  61 +               if (!rx_skb)
  62                         break;
  63
  64                 if (skb_queue_len(&rtwusb->rx_queue) >= RTW_USB_MAX_RXQ_LEN) {
  65                         dev_dbg_ratelimited(rtwdev->dev, "failed to get rx_queue, overflow\n");
  66 -                       dev_kfree_skb_any(skb);
  67 +                       dev_kfree_skb_any(rx_skb);
  68                         continue;
  69                 }
  70
  71 -               urb_len = skb->len;
  72 +               rx_desc = rx_skb->data;
  73
  74                 do {
  75 -                       rx_desc = skb->data;
  76                         rtw_rx_query_rx_desc(rtwdev, rx_desc, &pkt_stat,
  77                                              &rx_status);
  78                         pkt_offset = pkt_desc_sz + pkt_stat.drv_info_sz +
  79                                      pkt_stat.shift;
  80
  81 -                       next_pkt = round_up(pkt_stat.pkt_len + pkt_offset, 8);
  82 +                       skb_len = pkt_stat.pkt_len + pkt_offset;
  83 +                       if (skb_len > max_skb_len) {
  84 +                               rtw_dbg(rtwdev, RTW_DBG_USB,
  85 +                                       "skipping too big packet: %u\n",
  86 +                                       skb_len);
  87 +                               goto skip_packet;
  88 +                       }
  89 +
  90 +                       skb = alloc_skb(skb_len, GFP_KERNEL);
  91 +                       if (!skb) {
  92 +                               rtw_dbg(rtwdev, RTW_DBG_USB,
  93 +                                       "failed to allocate RX skb of size %u\n",
  94 +                                       skb_len);
  95 +                               goto skip_packet;
  96 +                       }
  97
  98 -                       if (urb_len >= next_pkt + pkt_desc_sz)
  99 -                               next_skb = skb_clone(skb, GFP_KERNEL);
 100 -                       else
 101 -                               next_skb = NULL;
 102 +                       skb_put_data(skb, rx_desc, skb_len);
 103
 104                         if (pkt_stat.is_c2h) {
 105 -                               skb_trim(skb, pkt_stat.pkt_len + pkt_offset);
 106                                 rtw_fw_c2h_cmd_rx_irqsafe(rtwdev, pkt_offset, skb);
 107                         } else {
 108                                 skb_pull(skb, pkt_offset);
 109 -                               skb_trim(skb, pkt_stat.pkt_len);
 110                                 rtw_update_rx_freq_for_invalid(rtwdev, skb,
 111                                                                &rx_status,
 112                                                                &pkt_stat);
 113 @@ -598,12 +608,12 @@ static void rtw_usb_rx_handler(struct wo
 114                                 ieee80211_rx_irqsafe(rtwdev->hw, skb);
 115                         }
 116
 117 -                       skb = next_skb;
 118 -                       if (skb)
 119 -                               skb_pull(skb, next_pkt);
 120 +skip_packet:
 121 +                       next_pkt = round_up(skb_len, 8);
 122 +                       rx_desc += next_pkt;
 123 +               } while (rx_desc + pkt_desc_sz < rx_skb->data + rx_skb->len);
 124
 125 -                       urb_len -= next_pkt;
 126 -               } while (skb);
 127 +               dev_kfree_skb_any(rx_skb);
 128         }
 129  }
 130