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wifi: rtw88: usb: Copy instead of cloning the RX skb

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"iperf3 -c 192.168.0.1 -R --udp -b 0" shows about 40% of datagrams
are lost. Many torrents don't download faster than 3 MiB/s, probably
because the Bittorrent protocol uses UDP. This is somehow related to
the use of skb_clone() in the RX path.

Don't use skb_clone(). Instead allocate a new skb for each 802.11 frame
received and copy the data from the big (32768 byte) skb.

With this patch, "iperf3 -c 192.168.0.1 -R --udp -b 0" shows only 1-2%
of datagrams are lost, and torrents can reach download speeds of 36
MiB/s.

Tested with RTL8812AU and RTL8822CU.

Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/8c9d4f9d-ebd8-4dc0-a0c4-9ebe430521dd@gmail.com
This commit is contained in:
Bitterblue Smith 2024-12-19 00:33:20 +02:00 committed by Ping-Ke Shih
parent 74a72c3675
commit e9048e2935
1 changed files with 31 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
drivers/net/wireless/realtek/rtw88/usb.c
View File

@ -7,6 +7,7 @@
#include <linux/mutex.h>
#include "main.h"
#include "debug.h"
#include "mac.h"
#include "reg.h"
#include "tx.h"
#include "rx.h"
@ -547,49 +548,58 @@ static void rtw_usb_rx_handler(struct work_struct *work)
{
struct rtw_usb *rtwusb = container_of(work, struct rtw_usb, rx_work);
struct rtw_dev *rtwdev = rtwusb->rtwdev;
const struct rtw_chip_info *chip = rtwdev->chip;
u32 pkt_desc_sz = chip->rx_pkt_desc_sz;
struct ieee80211_rx_status rx_status;
u32 pkt_offset, next_pkt, urb_len;
struct rtw_rx_pkt_stat pkt_stat;
struct sk_buff *next_skb;
struct sk_buff *rx_skb;
struct sk_buff *skb;
u32 pkt_desc_sz = rtwdev->chip->rx_pkt_desc_sz;
u32 max_skb_len = pkt_desc_sz + PHY_STATUS_SIZE * 8 +
IEEE80211_MAX_MPDU_LEN_VHT_11454;
u32 pkt_offset, next_pkt, skb_len;
u8 *rx_desc;
int limit;
for (limit = 0; limit < 200; limit++) {
skb = skb_dequeue(&rtwusb->rx_queue);
if (!skb)
rx_skb = skb_dequeue(&rtwusb->rx_queue);
if (!rx_skb)
break;
if (skb_queue_len(&rtwusb->rx_queue) >= RTW_USB_MAX_RXQ_LEN) {
dev_dbg_ratelimited(rtwdev->dev, "failed to get rx_queue, overflow\n");
dev_kfree_skb_any(skb);
dev_kfree_skb_any(rx_skb);
continue;
}
urb_len = skb->len;
rx_desc = rx_skb->data;
do {
rx_desc = skb->data;
rtw_rx_query_rx_desc(rtwdev, rx_desc, &pkt_stat,
&rx_status);
pkt_offset = pkt_desc_sz + pkt_stat.drv_info_sz +
pkt_stat.shift;
next_pkt = round_up(pkt_stat.pkt_len + pkt_offset, 8);
skb_len = pkt_stat.pkt_len + pkt_offset;
if (skb_len > max_skb_len) {
rtw_dbg(rtwdev, RTW_DBG_USB,
"skipping too big packet: %u\n",
skb_len);
goto skip_packet;
}
if (urb_len >= next_pkt + pkt_desc_sz)
next_skb = skb_clone(skb, GFP_KERNEL);
else
next_skb = NULL;
skb = alloc_skb(skb_len, GFP_KERNEL);
if (!skb) {
rtw_dbg(rtwdev, RTW_DBG_USB,
"failed to allocate RX skb of size %u\n",
skb_len);
goto skip_packet;
}
skb_put_data(skb, rx_desc, skb_len);
if (pkt_stat.is_c2h) {
skb_trim(skb, pkt_stat.pkt_len + pkt_offset);
rtw_fw_c2h_cmd_rx_irqsafe(rtwdev, pkt_offset, skb);
} else {
skb_pull(skb, pkt_offset);
skb_trim(skb, pkt_stat.pkt_len);
rtw_update_rx_freq_for_invalid(rtwdev, skb,
&rx_status,
&pkt_stat);
@ -598,12 +608,12 @@ static void rtw_usb_rx_handler(struct work_struct *work)
ieee80211_rx_irqsafe(rtwdev->hw, skb);
}
skb = next_skb;
if (skb)
skb_pull(skb, next_pkt);
skip_packet:
next_pkt = round_up(skb_len, 8);
rx_desc += next_pkt;
} while (rx_desc + pkt_desc_sz < rx_skb->data + rx_skb->len);
urb_len -= next_pkt;
} while (skb);
dev_kfree_skb_any(rx_skb);
}
}