On Fri, Aug 18, 2023 at 9:57 AM Sebastian Andrzej Siewior
[off-list ref] wrote:

On 2023-08-18 09:43:08 [-0500], Yan Zhai wrote:

quoted

quoted

Looking at the cloudflare ppl here in the thread, I doubt they use
backlog but have proper NAPI so they might not need this.

Cloudflare does have backlog usage. On some veths we have to turn GRO

Oh. Okay.

quoted

off to cope with multi-layer encapsulation, and there is also no XDP
attached on these interfaces, thus the backlog is used. There are also
other usage of backlog, tuntap, loopback and bpf-redirect ingress.
Frankly speaking, making a NAPI instance "threaded" itself is not a
concern. We have threaded NAPI running on some veth for quite a while,
and it performs pretty well. The concern, if any, would be the
maturity of new code. I am happy to help derisk with some lab tests
and dogfooding if generic agreement is reached to proceed with this
idea.

If you have threaded NAPI for veth then you wouldn't be affected by this
code. However, if you _are_ affected by this and you use veth it would
be helpful to figure out if you have problems as of net-next and if this
helps or makes it worse.

yes we are still impacted on non-NAPI veths and other scenarios. But
net-next sounds good, still plenty of time to evaluate if it has any
negative impact.

Yan

As of now Jakub isn't eager to have it and my testing/ convincing is
quite limited. If nobody else yells that something like that would be
helpful I would simply go and convince PeterZ/tglx to apply 2/2 of this
series.

quoted

Yan

Sebastian