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

[Paolo Abeni <pabeni@redhat.com>]

Hi,

On 2/14/25 6:07 PM, Breno Leitao 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>
> ---
> ---
> Changes in v2:
> - Close the parenthesis in a new line to honor the tcp.h format (Jakub).
> - Add the bpftrace example in the commit message (Jakub)
> - Link to v1: https://lore.kernel.org/r/20250207-cwnd_tracepoint-v1-1-13650f3ca96d@debian.org

For future similar situations, note that it's expected to carry-on the
tag already collected in the previous versions, since the delta is only
cosmetic.

No further actions required on your side.

Cheers,

Paolo