From: Andrew Lunn <andrew@lunn.ch>
To: Rosen Penev <rosenp@gmail.com>
Cc: netdev@vger.kernel.org, Chris Snook <chris.snook@gmail.com>,
Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@kernel.org>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net-next] net: ag71xx: align the IP header behind DSA tags
Date: Wed, 7 Oct 2026 20:27:50 +0200 [thread overview]
Message-ID: <d89d6b2f-3ff3-4f76-9b77-7e59d16ed482@lunn.ch> (raw)
In-Reply-To: <20261007174449.671416-1-rosenp@gmail.com>
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@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Andrew
prev parent reply other threads:[~2026-10-07 18:28 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-07 17:44 Rosen Penev
2026-10-07 18:27 ` Andrew Lunn [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=d89d6b2f-3ff3-4f76-9b77-7e59d16ed482@lunn.ch \
--to=andrew@lunn.ch \
--cc=andrew+netdev@lunn.ch \
--cc=chris.snook@gmail.com \
--cc=davem@davemloft.net \
--cc=edumazet@kernel.org \
--cc=kuba@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=rosenp@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®