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Date: Wed, 21 Dec 2022 16:59:24 +0900
From: Leesoo Ahn <lsahn@...eel.net>
To: lsahn@...eel.net
Cc: Oliver Neukum <oneukum@...e.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Greg KH <greg@...ah.com>,
netdev@...r.kernel.org, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v3] usbnet: optimize usbnet_bh() to reduce CPU load
The current source pushes skb into dev->done queue by calling
skb_queue_tail() and then pop it by calling 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 jumping to rx_cleanup
state directly to free them instead of calling skb_queue_tail() and
skb_dequeue() for push/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@...eel.net>
---
v3:
- Replace return values with proper -ERR values in rx_process()
v2:
- Replace goto label with return statement to reduce goto entropy
- Add CPU load information by perf in commit message
v1 at:
https://patchwork.kernel.org/project/netdevbpf/patch/20221217161851.829497-1-lsahn@ooseel.net/
---
drivers/net/usb/usbnet.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 64a9a80b2309..98d594210df4 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -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;
}
/*-------------------------------------------------------------------------*/
@@ -1528,13 +1526,14 @@ 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))
+ goto cleanup;
continue;
case tx_done:
kfree(entry->urb->sg);
fallthrough;
case rx_cleanup:
+cleanup:
usb_free_urb (entry->urb);
dev_kfree_skb (skb);
continue;
--
2.34.1
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