Re: [PATCH net-next v2] trace: tcp: Add tracepoint for tcp_cwnd_reduction()

On Fri, Feb 14, 2025 at 6:07 PM Breno Leitao [off-list ref] wrote:

Add a lightweight tracepoint to monitor TCP congestion window
adjustments via tcp_cwnd_reduction(). This tracepoint enables tracking
of:
- TCP window size fluctuations
- Active socket behavior
- Congestion window reduction events

Meta has been using BPF programs to monitor this function for years.
Adding a proper tracepoint provides a stable API for all users who need
to monitor TCP congestion window behavior.

Use DECLARE_TRACE instead of TRACE_EVENT to avoid creating trace event
infrastructure and exporting to tracefs, keeping the implementation
minimal. (Thanks Steven Rostedt)

Given that this patch creates a rawtracepoint, you could hook into it
using regular tooling, like bpftrace, using regular rawtracepoint
infrastructure, such as:

        rawtracepoint:tcp_cwnd_reduction_tp {
                ....
        }

Signed-off-by: Breno Leitao <leitao@debian.org>

Reviewed-by: Eric Dumazet <edumazet@google.com>