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usbnet: optimize usbnet_bh() to reduce CPU load 

The current source pushes skb into dev-done queue by calling
skb_dequeue_tail() and then pop it by skb_dequeue() to branch to
rx_cleanup state for freeing urb/skb in usbnet_bh(). It takes extra CPU
load, 2.21% (skb_queue_tail) as follows,

-   11.58%     0.26%  swapper          [k] usbnet_bh
   - 11.32% usbnet_bh
      - 6.43% skb_dequeue
           6.34% _raw_spin_unlock_irqrestore
      - 2.21% skb_queue_tail
           2.19% _raw_spin_unlock_irqrestore
      - 1.68% consume_skb
         - 0.97% kfree_skbmem
              0.80% kmem_cache_free
           0.53% skb_release_data

To reduce the extra CPU load use return values to call helper function
usb_free_skb() to free the resources instead of calling skb_queue_tail()
and skb_dequeue() for push and pop respectively.

-    7.87%     0.25%  swapper          [k] usbnet_bh
   - 7.62% usbnet_bh
      - 4.81% skb_dequeue
           4.74% _raw_spin_unlock_irqrestore
      - 1.75% consume_skb
         - 0.98% kfree_skbmem
              0.78% kmem_cache_free
           0.58% skb_release_data
        0.53% smsc95xx_rx_fixup

Signed-off-by: Leesoo Ahn <lsahn@ooseel.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Leesoo Ahn 2023-01-06 19:49:49 +09:00 committed by David S. Miller
parent 9cb8bae3d1
commit fb59bf28cd
1 changed files with 17 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
drivers/net/usb/usbnet.c
View File

@ -555,32 +555,30 @@ static int rx_submit (struct usbnet *dev, struct urb *urb, gfp_t flags)
/*-------------------------------------------------------------------------*/
static inline void rx_process (struct usbnet *dev, struct sk_buff *skb)
static inline int rx_process(struct usbnet *dev, struct sk_buff *skb)
{
if (dev->driver_info->rx_fixup &&
!dev->driver_info->rx_fixup (dev, skb)) {
/* With RX_ASSEMBLE, rx_fixup() must update counters */
if (!(dev->driver_info->flags & FLAG_RX_ASSEMBLE))
dev->net->stats.rx_errors++;
goto done;
return -EPROTO;
}
// else network stack removes extra byte if we forced a short packet
/* all data was already cloned from skb inside the driver */
if (dev->driver_info->flags & FLAG_MULTI_PACKET)
goto done;
return -EALREADY;
if (skb->len < ETH_HLEN) {
dev->net->stats.rx_errors++;
dev->net->stats.rx_length_errors++;
netif_dbg(dev, rx_err, dev->net, "rx length %d\n", skb->len);
} else {
usbnet_skb_return(dev, skb);
return;
return -EPROTO;
}
done:
skb_queue_tail(&dev->done, skb);
usbnet_skb_return(dev, skb);
return 0;
}
/*-------------------------------------------------------------------------*/
@ -1514,6 +1512,14 @@ err:
return ret;
}
static inline void usb_free_skb(struct sk_buff *skb)
{
struct skb_data *entry = (struct skb_data *)skb->cb;
usb_free_urb(entry->urb);
dev_kfree_skb(skb);
}
/*-------------------------------------------------------------------------*/
// tasklet (work deferred from completions, in_irq) or timer
@ -1528,15 +1534,14 @@ static void usbnet_bh (struct timer_list *t)
entry = (struct skb_data *) skb->cb;
switch (entry->state) {
case rx_done:
entry->state = rx_cleanup;
rx_process (dev, skb);
if (rx_process(dev, skb))
usb_free_skb(skb);
continue;
case tx_done:
kfree(entry->urb->sg);
fallthrough;
case rx_cleanup:
usb_free_urb (entry->urb);
dev_kfree_skb (skb);
usb_free_skb(skb);
continue;
default:
netdev_dbg(dev->net, "bogus skb state %d\n", entry->state);