Re: [PATCH net-next] net: ag71xx: align the IP header behind DSA tags

[Rosen Penev]

On Fri, Oct 9, 2026 at 9:47 AM Simon Horman <horms@xxxxxxxxxx> wrote:
>
> On Wed, Oct 07, 2026 at 10:44:49AM -0700, Rosen Penev wrote:
> > The receive buffer offset includes NET_IP_ALIGN to get the IP header
> > aligned behind a 14 byte Ethernet header. Most ag71xx devices use DSA
> > switches whose tag sits in front of the EtherType, which moves the IP
> > header by another 2 bytes. Every access to the IP and TCP headers then
> > traps and gets emulated by the unaligned access handler, around 6 times
> > per forwarded frame.
> >
> > Take the headroom needed by the DSA tagger into account when choosing
> > the offset.
> >
> > TP-Link Archer C7 v2 (qca8k), median of 3 runs, Mbit/s:
> >
> >                        before   after
> >   routed up               743     855
> >   routed down             660     749
> >   local receive           554     572
> >
> > The unaligned instruction counter no longer moves while forwarding.
> >
> > Assisted-by: LLM
> > Signed-off-by: Rosen Penev <rosenp@xxxxxxxxx>
>
> Unfortunately this patch did not apply cleanly to net-next at the time it
> was posted, so our CI did not run.
It appears I was careless and sent it ahead of local commits. Will resend.
>
> Please rebase and repost.
>
> --
> pw-bot: changes-requested