Re: [PATCH RFC net-next 0/9] net: BPF Timestamping 2.0 for TCP

["Alexei Starovoitov" <alexei.starovoitov@gmail.com>]

On Sat Sep 19, 2026 at 2:37 PM UTC, Jason Xing wrote:
> From: Jason Xing <kernelxing@gmail.com>
>
> Greeting,
>
> It's BPF Timestamping 2.0 that aims to observe the packet latency
> more efficiently and simply for different protocols. The current
> series is only focused on TCP protocol.
>
> At Netdev 0x1a/Netconf 2026, the history, background, motivation and
> rough implementation of the feature were exhaustively introduced[1].
>
> History
> =======
> - In 2009, Patrick Ohly implemented the basic infrastructure
> - In 2014, Willem de Bruijn enhanced the TCP latency observation
> - In 2024, Jason Xing proposed its lightweight BPF version
> Detailed slides from 28 to 32 [1].
>
> Background
> ==========
> Even though BPF Timetamping 1.0 is comparatively low-overhead,
> transparent, it's still complicated due to a few points inherited
> from the design:
> - Inflexible/fixed reporting phases (qdisc/driver/ack)
>   When we confirm the issue arises from the kernel by using attribution
>   ability of timestamping feature, we need to further minimize the scope
>   until the issue is fixed. That means, we then have to resort to write
>   a few complex BPF progs with the similar functionalities (like skb
>   level tag) which should not happen.
> - Not enough low-overhead
>   Serving the sensitive applications, an always-on latency observation
>   platform should mitigate the self-impact as much as possible. As we
>   can conclude from BPF Timestamping selftests, there are some blocking
>   and time-consuming points like where reading/writing BPF maps happen
>   in the extremely hot paths.
> - Minor flaws
>   There are a few minor flaws inherited from the initial design, like
>   missing tagging the last packet[2][3][4].


All these "issues" sound minor and on their own do not warrant new uapi.

This RFC don't even have an example of how it could be used end-to-end.

So soft nack from me for now.

pw-bot: cr