* NAPI on USB network drivers
@ 2017-01-25 9:34 Oliver Neukum
[not found] ` <1485336881.16604.2.camel-IBi9RG/b67k@public.gmane.org>
2017-01-25 19:32 ` David Miller
0 siblings, 2 replies; 8+ messages in thread
From: Oliver Neukum @ 2017-01-25 9:34 UTC (permalink / raw)
To: Hayes Wang; +Cc: netdev, linux-usb
Hi,
looking at r8152 I noticed that it uses NAPI. I never considered
this for the generic USB networking code as you cannot disable
interrupts for USB. Is it still worth it? What are the benefits?
Regards
Oliver
^ permalink raw reply [flat|nested] 8+ messages in thread
* RE: NAPI on USB network drivers
[not found] ` <1485336881.16604.2.camel-IBi9RG/b67k@public.gmane.org>
@ 2017-01-25 9:39 ` Hayes Wang
[not found] ` <0835B3720019904CB8F7AA43166CEEB201A134A7-JIZ+AM9kKNzKeZCINmmWEypo8c9IxeqyAjHCUHv49ws@public.gmane.org>
2017-01-25 14:13 ` Eric Dumazet
0 siblings, 2 replies; 8+ messages in thread
From: Hayes Wang @ 2017-01-25 9:39 UTC (permalink / raw)
To: Oliver Neukum
Cc: netdev-u79uwXL29TY76Z2rM5mHXA, linux-usb-u79uwXL29TY76Z2rM5mHXA
Oliver Neukum [mailto:oneukum@suse.com]
> Sent: Wednesday, January 25, 2017 5:35 PM
[...]
> looking at r8152 I noticed that it uses NAPI. I never considered
> this for the generic USB networking code as you cannot disable
> interrupts for USB. Is it still worth it? What are the benefits?
You could use napi_gro_receive() and it influences the performance.
Best Regards,
Hayes
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: NAPI on USB network drivers
[not found] ` <0835B3720019904CB8F7AA43166CEEB201A134A7-JIZ+AM9kKNzKeZCINmmWEypo8c9IxeqyAjHCUHv49ws@public.gmane.org>
@ 2017-01-25 13:33 ` Oliver Hartkopp
2017-01-25 20:57 ` Alexander Duyck
0 siblings, 1 reply; 8+ messages in thread
From: Oliver Hartkopp @ 2017-01-25 13:33 UTC (permalink / raw)
To: Hayes Wang, Oliver Neukum
Cc: netdev-u79uwXL29TY76Z2rM5mHXA, linux-usb-u79uwXL29TY76Z2rM5mHXA
On 01/25/2017 10:39 AM, Hayes Wang wrote:
> Oliver Neukum [mailto:oneukum-IBi9RG/b67k@public.gmane.org]
>> Sent: Wednesday, January 25, 2017 5:35 PM
> [...]
>> looking at r8152 I noticed that it uses NAPI. I never considered
>> this for the generic USB networking code as you cannot disable
>> interrupts for USB. Is it still worth it? What are the benefits?
>
> You could use napi_gro_receive() and it influences the performance.
Another positive effect with NAPI is that you won't face out-of-order
ethernet frames as you get with non-NAPI drivers, e.g. ax88179_178a
http://marc.info/?l=linux-can&m=148049063812807&w=2
We have the issue with CAN drivers where all USB drivers and >90% of the
I/O mapped drivers do not use NAPI.
I wonder whether it makes sense to add NAPI to a driver which only has
ONE RX buffer ... but when searching for a solution for o-o-o frames I
was always pointed to NAPI.
Regards,
Oliver
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: NAPI on USB network drivers
2017-01-25 9:39 ` Hayes Wang
[not found] ` <0835B3720019904CB8F7AA43166CEEB201A134A7-JIZ+AM9kKNzKeZCINmmWEypo8c9IxeqyAjHCUHv49ws@public.gmane.org>
@ 2017-01-25 14:13 ` Eric Dumazet
[not found] ` <1485353591.5145.8.camel-XN9IlZ5yJG9HTL0Zs8A6p+yfmBU6pStAUsxypvmhUTTZJqsBc5GL+g@public.gmane.org>
1 sibling, 1 reply; 8+ messages in thread
From: Eric Dumazet @ 2017-01-25 14:13 UTC (permalink / raw)
To: Hayes Wang; +Cc: Oliver Neukum, netdev, linux-usb
On Wed, 2017-01-25 at 09:39 +0000, Hayes Wang wrote:
> Oliver Neukum [mailto:oneukum@suse.com]
> > Sent: Wednesday, January 25, 2017 5:35 PM
> [...]
> > looking at r8152 I noticed that it uses NAPI. I never considered
> > this for the generic USB networking code as you cannot disable
> > interrupts for USB. Is it still worth it? What are the benefits?
>
> You could use napi_gro_receive() and it influences the performance.
You also could use napi_complete_done() instead of napi_complete(), as
it allows users to tune the performance vs latency for GRO.
Looking at this driver, I do not see any limitation on the number of
skbs that can be pushed into tp->rx_queue.
I wonder if this queue can end up consuming all memory of a host under
stress.
diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index e1466b4d2b6c727148a884672bbd9593bf04b3ac..221df4a931b5c1073f1922d0fa0bbff158c73b7d 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -1840,7 +1840,10 @@ static int rx_bottom(struct r8152 *tp, int budget)
stats->rx_packets++;
stats->rx_bytes += pkt_len;
} else {
- __skb_queue_tail(&tp->rx_queue, skb);
+ if (unlikely(skb_queue_len(&tp->rx_queue) >= 1000))
+ kfree_skb(skb);
+ else
+ __skb_queue_tail(&tp->rx_queue, skb);
}
find_next_rx:
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: NAPI on USB network drivers
2017-01-25 9:34 NAPI on USB network drivers Oliver Neukum
[not found] ` <1485336881.16604.2.camel-IBi9RG/b67k@public.gmane.org>
@ 2017-01-25 19:32 ` David Miller
1 sibling, 0 replies; 8+ messages in thread
From: David Miller @ 2017-01-25 19:32 UTC (permalink / raw)
To: oneukum; +Cc: hayeswang, netdev, linux-usb
From: Oliver Neukum <oneukum@suse.com>
Date: Wed, 25 Jan 2017 10:34:41 +0100
> looking at r8152 I noticed that it uses NAPI. I never considered
> this for the generic USB networking code as you cannot disable
> interrupts for USB. Is it still worth it? What are the benefits?
I think it's not a good approach for getting GRO.
Exactly because of the issue you raise, in that USB drivers
cannot stop the URBs from coming in while running their poll
method.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: NAPI on USB network drivers
2017-01-25 13:33 ` Oliver Hartkopp
@ 2017-01-25 20:57 ` Alexander Duyck
2017-01-26 18:59 ` Oliver Hartkopp
0 siblings, 1 reply; 8+ messages in thread
From: Alexander Duyck @ 2017-01-25 20:57 UTC (permalink / raw)
To: Oliver Hartkopp; +Cc: Hayes Wang, Oliver Neukum, netdev, linux-usb
On Wed, Jan 25, 2017 at 5:33 AM, Oliver Hartkopp <socketcan@hartkopp.net> wrote:
> On 01/25/2017 10:39 AM, Hayes Wang wrote:
>>
>> Oliver Neukum [mailto:oneukum@suse.com]
>>>
>>> Sent: Wednesday, January 25, 2017 5:35 PM
>>
>> [...]
>>>
>>> looking at r8152 I noticed that it uses NAPI. I never considered
>>> this for the generic USB networking code as you cannot disable
>>> interrupts for USB. Is it still worth it? What are the benefits?
>>
>>
>> You could use napi_gro_receive() and it influences the performance.
>
>
> Another positive effect with NAPI is that you won't face out-of-order
> ethernet frames as you get with non-NAPI drivers, e.g. ax88179_178a
>
> http://marc.info/?l=linux-can&m=148049063812807&w=2
>
> We have the issue with CAN drivers where all USB drivers and >90% of the I/O
> mapped drivers do not use NAPI.
>
> I wonder whether it makes sense to add NAPI to a driver which only has ONE
> RX buffer ... but when searching for a solution for o-o-o frames I was
> always pointed to NAPI.
>
> Regards,
> Oliver
>
You could probably get around the o-o-o problem by enabling RPS for
the interface. I have found that it works for me to do that in order
to resolve o-o-o frames generated by VMs on virtual interfaces that
can't use NAPI.
- Alex
^ permalink raw reply [flat|nested] 8+ messages in thread
* RE: NAPI on USB network drivers
[not found] ` <1485353591.5145.8.camel-XN9IlZ5yJG9HTL0Zs8A6p+yfmBU6pStAUsxypvmhUTTZJqsBc5GL+g@public.gmane.org>
@ 2017-01-26 1:43 ` Hayes Wang
0 siblings, 0 replies; 8+ messages in thread
From: Hayes Wang @ 2017-01-26 1:43 UTC (permalink / raw)
To: Eric Dumazet
Cc: Oliver Neukum, netdev-u79uwXL29TY76Z2rM5mHXA,
linux-usb-u79uwXL29TY76Z2rM5mHXA
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="utf-8", Size: 1287 bytes --]
Eric Dumazet [mailto:eric.dumazet@gmail.com]
> Sent: Wednesday, January 25, 2017 10:13 PM
[...]
> You also could use napi_complete_done() instead of napi_complete(), as
> it allows users to tune the performance vs latency for GRO.
>
> Looking at this driver, I do not see any limitation on the number of
> skbs that can be pushed into tp->rx_queue.
>
> I wonder if this queue can end up consuming all memory of a host under
> stress.
>
> diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
> index
> e1466b4d2b6c727148a884672bbd9593bf04b3ac..221df4a931b5c1073f1922d0fa0b
> bff158c73b7d 100644
> --- a/drivers/net/usb/r8152.c
> +++ b/drivers/net/usb/r8152.c
> @@ -1840,7 +1840,10 @@ static int rx_bottom(struct r8152 *tp, int budget)
> stats->rx_packets++;
> stats->rx_bytes += pkt_len;
> } else {
> - __skb_queue_tail(&tp->rx_queue, skb);
> + if (unlikely(skb_queue_len(&tp->rx_queue) >= 1000))
> + kfree_skb(skb);
> + else
> + __skb_queue_tail(&tp->rx_queue, skb);
> }
>
> find_next_rx:
Thanks for your suggestion. I would submit it later.
Best Regards,
Hayes
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: NAPI on USB network drivers
2017-01-25 20:57 ` Alexander Duyck
@ 2017-01-26 18:59 ` Oliver Hartkopp
0 siblings, 0 replies; 8+ messages in thread
From: Oliver Hartkopp @ 2017-01-26 18:59 UTC (permalink / raw)
To: Alexander Duyck; +Cc: Hayes Wang, Oliver Neukum, netdev, linux-usb
On 01/25/2017 09:57 PM, Alexander Duyck wrote:
> On Wed, Jan 25, 2017 at 5:33 AM, Oliver Hartkopp <socketcan@hartkopp.net> wrote:
>
> You could probably get around the o-o-o problem by enabling RPS for
> the interface. I have found that it works for me to do that in order
> to resolve o-o-o frames generated by VMs on virtual interfaces that
> can't use NAPI.
Sounds promising!
In fact I tried to fix this o-o-o stuff here:
http://marc.info/?l=linux-can&m=143637774606287&w=2
Do you have an example how to do it right?
Best regards,
Oliver
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2017-01-26 18:59 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
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2017-01-25 9:34 NAPI on USB network drivers Oliver Neukum
[not found] ` <1485336881.16604.2.camel-IBi9RG/b67k@public.gmane.org>
2017-01-25 9:39 ` Hayes Wang
[not found] ` <0835B3720019904CB8F7AA43166CEEB201A134A7-JIZ+AM9kKNzKeZCINmmWEypo8c9IxeqyAjHCUHv49ws@public.gmane.org>
2017-01-25 13:33 ` Oliver Hartkopp
2017-01-25 20:57 ` Alexander Duyck
2017-01-26 18:59 ` Oliver Hartkopp
2017-01-25 14:13 ` Eric Dumazet
[not found] ` <1485353591.5145.8.camel-XN9IlZ5yJG9HTL0Zs8A6p+yfmBU6pStAUsxypvmhUTTZJqsBc5GL+g@public.gmane.org>
2017-01-26 1:43 ` Hayes Wang
2017-01-25 19:32 ` David Miller
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