W dniu 9/16/25 o 12:43, Sabrina Dubroca pisze: > 2025-09-09, 16:43:01 +0200, Marek Mietus wrote: >> W dniu 9/9/25 o 13:17, Antonio Quartulli pisze: >>> On 09/09/2025 07:43, Marek Mietus wrote: >>>> Currently, all xmit flows use dst_cache in a way that references >>>> its dst_entry for each xmitted packet. These atomic operations >>>> are redundant in some flows. >>> >>> Can you elaborate on the current limits/drawbacks and explain what we gain >>> with this new approach? >>> >>> It may be obvious for some, but it's not for me. >>> >> >> The only difference with the new approach is that we avoid taking an >> unnecessary >> reference on dst_entry. This is possible since the entire flow is protected >> by RCU. >> This change reduces an atomic write operation on every xmit, resulting in a >> performance >> improvement. > > It would be nice to incorporate this information into the cover > letter, and to provide numbers showing the performance > improvement. That way, it's available to other reviewers and gets > recorded in the git log. Are you doing crypto with some accelerator? > Otherwise I'd imagine skipping a few atomic operations is not really > noticeable. > >> There are other flows in the kernel where a similar approach is used (e.g. >> __ip_queue_xmit >> uses skb_dst_set_noref). >> >>> Also it sounded as if more tunnels were affected, but in the end only ovpn >>> is being changed. >>> Does it mean all other tunnels don't need this? >>> >> >> More tunneling code can be updated to utilize these new helpers. I only >> worked >> on OpenVPN, as I am more familiar with it. It was very easy to implement the >> changes in OpenVPN because it doesn't use the udp_tunnel_dst_lookup helper >> that adds some complexity. >> >> I hope to incorporate these changes in more tunnels in the future. > > It would also be good to add this to the cover letter. Something like > "For now, only ovpn is updated <for $reason>, but other tunnels could > also take advantage of this." >
Noted, will add in the next revision. _______________________________________________ Openvpn-devel mailing list Openvpn-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/openvpn-devel
