Re: [PATCH net-next v3 0/3] net: tunnel: introduce noref xmit flows for tunnels

[Jakub Kicinski <kuba@kernel.org>]

On Mon, 22 Sep 2025 13:06:19 +0200 Marek Mietus wrote:
> This patchset introduces new noref xmit helpers and incorporates
> them in the OpenVPN driver. A similar improvement can also be
> applied to other tunnel code in the future. The implementation
> for OpenVPN is a good starting point as it doesn't use the
> udp_tunnel_dst_lookup helper which adds some complexity.

You're basically refactoring an API, it's fairly unusual to leave both
APIs in place upstream. Unless the number of callers is really huge,
say >100, or complexity very high. Not sure how others feel but IMHO
you should try to convert all the tunnels.

> There are already noref optimizations in both ipv4 and ip6 
> (See __ip_queue_xmit, inet6_csk_xmit). This patchset allows for
> similar optimizations in udp tunnels. Referencing the dst_entry
> is now redundant, as the entire flow is protected under RCU, so
> it is removed.
> 
> With this patchset, I was able to observe a 4% decrease in the total
> time for ovpn_udp_send_skb using perf.

Please provide more meaningful perf wins. Relative change of perf in
one function doesn't tell use.. well.. anything.

Please do not remove the diff stat generated by git in the cover
letter.