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. Cheers, Paolo
