netdev - Re: [PATCH net-next v2 0/9] xsk: improvement performance in copy mode

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Message-ID: <CAL+tcoCa3nfO+PJE-uccnOfQaZnUa+78AmJXwjaLod4WvPPfog@mail.gmail.com>
Date: Tue, 26 Aug 2025 08:51:24 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, edumazet@...gle.com, 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, 
	horms@...nel.org, andrew+netdev@...n.ch, bpf@...r.kernel.org, 
	netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v2 0/9] xsk: improvement performance in copy mode

On Tue, Aug 26, 2025 at 8:29 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Tue, 26 Aug 2025 08:01:03 +0800 Jason Xing wrote:
> > On Tue, Aug 26, 2025 at 1:44 AM Jakub Kicinski <kuba@...nel.org> wrote:
> > > On Mon, 25 Aug 2025 21:53:33 +0800 Jason Xing wrote:
> > > > copy mode:   1,109,754 pps
> > > > batch mode:  2,393,498 pps (+115.6%)
> > > > xmit.more:   3,024,110 pps (+172.5%)
> > > > zc mode:    14,879,414 pps
> > >
> > > I've asked you multiple times to add comparison with the performance
> > > of AF_PACKET. What's the disconnect?
> >
> > Sorry for missing the question. I'm not very familiar with how to run the
> > test based on AF_PACKET. Could you point it out for me? Thanks.
> >
> > I remember the very initial version of AF_XDP was pure AF_PACKET. So
> > may I ask why we expect to see the comparison between them?
>
> Pretty sure I told you this at least twice but the point of AF_XDP
> is the ZC mode. Without a comparison to AF_PACKET which has similar
> functionality optimizing AF_XDP copy mode seems unjustified.

Oh, I see. Let me confirm again that you expect to see a demo like the
copy mode of AF_PACKET v4 [1] and see the differences in performance,
right?

If AF_PACKET eventually outperforms AF_XDP, do we need to reinvent the
copy mode based on AF_PACKET?

And if a quick/simple implementation is based on AF_PACKET, it
shouldn't be that easy to use the same benchmark to see which one is
better. That means inventing a new unified benchmark tool is
necessary?

[1]: https://lore.kernel.org/all/20171031124145.9667-1-bjorn.topel@gmail.com/

Thanks,
Jason