netdev - Re: [PATCH net-next 0/2] net: xsk: add two sysctl knobs

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Message-ID: <CAL+tcoC9_ipqoj_egPJ82sXSrT-g-JM_MrCMm1N0JePd2LGf-Q@mail.gmail.com>
Date: Thu, 19 Jun 2025 03:24:30 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: Stanislav Fomichev <stfomichev@...il.com>, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, bjorn@...nel.org, 
	magnus.karlsson@...el.com, maciej.fijalkowski@...el.com, 
	jonathan.lemon@...il.com, sdf@...ichev.me, ast@...nel.org, 
	daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com, 
	bpf@...r.kernel.org, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next 0/2] net: xsk: add two sysctl knobs

On Thu, Jun 19, 2025 at 1:58 AM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> Jason Xing wrote:
> > Hi Stanislav,
> >
> > On Tue, Jun 17, 2025 at 9:11 AM Stanislav Fomichev <stfomichev@...il.com> wrote:
> > >
> > > On 06/17, Jason Xing wrote:
> > > > From: Jason Xing <kernelxing@...cent.com>
> > > >
> > > > Introduce a control method in the xsk path to let users have the chance
> > > > to tune it manually.
> > >
> > > Can you expand more on why the defaults don't work for you?
> >
> > We use a user-level tcp stack with xsk to transmit packets that have
> > higher priorities than other normal kernel tcp flows. It turns out
> > that enlarging the number can minimize times of triggering sendto
> > sysctl, which contributes to faster transmission. it's very easy to
> > hit the upper bound (namely, 32) if you log the return value of
> > sendto. I mentioned a bit about this in the second patch, saying that
> > we can have a similar knob already appearing in the qdisc layer.
> > Furthermore, exposing important parameters can help applications
> > complete their AI/auto-tuning to judge which one is the best fit in
> > their production workload. That is also one of the promising
> > tendencies :)
>
> It would be informative to include this in the commit.

Sure, I will add more in V3.

>
> Or more broadly: suggestions for when and how to pick good settings
> for these new tunables.

I'm not sure what is a good setting in general. But I will try to
describe how I use it and what my understanding of it is in the commit
message.

Thanks,
Jason