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Date: Wed, 21 Dec 2022 16:50:39 +0900 From: Leesoo Ahn <lsahn@...eel.net> To: Greg KH <greg@...ah.com> 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>, netdev@...r.kernel.org, linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2] usbnet: optimize usbnet_bh() to reduce CPU load On 22. 12. 21. 16:30, Greg KH wrote: > On Wed, Dec 21, 2022 at 04:19:45PM +0900, Leesoo Ahn wrote: >> On 22. 12. 21. 15:32, Greg KH wrote: >>> On Wed, Dec 21, 2022 at 01:42:30PM +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@...eel.net> >>>> --- >>>> 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..6e82fef90dd9 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 1; >>> "1" means that you processed 1 byte, not that this is an error, which is >>> what you want to say here, right? >> No not at all.. >>> Please return a negative error value >>> like I asked this to be changed to last time :( >> Could you help me to decide the message type at this point please? I am >> confused. > I do not know, pick something that seems correct and we can go from > there. The important thing is that it is a -ERR value, not a positive > one as that makes no sense for kernel functions. Thank you for reviewing, v3 will be sent soon. Best regards, Leesoo
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