Subject: Re: [PATCH v3 net-next 2/4] net: Allow to use SMP threads for backlog NAPI.

From: Sebastian Andrzej Siewior <[email-masked]>
Date: Tue, 5 Mar 2024 11:52:18 +0100

On 2024-03-05 11:44:06 [+0100], Paolo Abeni wrote:
> > I am not aware of a perf regression.
> 
> I probably inferred too much from the udp lookback case.

Yes. This was real and is gone now :)

> > Jakub was worried about a possible regression with this and while asking
> > nobody came up with an actual use case where this is used. So it is as
> > he suggested, optional for everyone but forced-enabled for RT where it
> > is required.
> > I had RH benchmarking this and based on their 25Gbe and 50Gbe NICs and
> > the results look good. If anything it looked a bit better with this on
> > the 50Gbe NICs but since those NICs have RSS…
> > 
> > I have this default off so that nobody complains and yet has to
> > possibility to test and see if it leads to a problem. If not, we could
> > enable it by default and after a few cycles and then remove the IPI code
> > a few cycles later with absent complains.
> 
> I think this late in the cycle is better to keep backlog threads off by
> default.

Sure.

> Thanks,
> Paolo

Seastian