22. 12. 22. 20:13에 Paolo Abeni 이(가) 쓴 글:
On Wed, 2022-12-21 at 16:59 +0900, Leesoo Ahn wrote: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@xxxxxxxxxx> --- 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@xxxxxxxxxx/This looks like net-next material. We have already submitted the networking pull request to Linus for v6.2 and therefore net-next is closed for new drivers, features, code refactoring and optimizations. We are currently accepting bug fixes only. Please repost when net-next reopens after Jan 2nd, including the expected 'net-next' tag into the subject line RFC patches sent for review only are obviously welcome at any time. [...]@@ -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;You can avoid this additional label (which is a little confusing inside a switch) factoring out a usb_free_skb(skb) helper and calling it here and under the rx_cleanup case.
Thank you for the information and feedback, it will be in v4 when net-next reopens.
Best regards, Leesoo
