From: Breno Leitao Date: Fri, 14 Feb 2025 17:07:11 +0000 (-0800) Subject: trace: tcp: Add tracepoint for tcp_cwnd_reduction() X-Git-Tag: v6.15-rc1~160^2~295 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8e677a466145174e6899ceaf189e7cb7fbd6ad3f;p=thirdparty%2Flinux.git trace: tcp: Add tracepoint for tcp_cwnd_reduction() 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 Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20250214-cwnd_tracepoint-v2-1-ef8d15162d95@debian.org Signed-off-by: Paolo Abeni --- diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h index a27c4b619dffd..1a40c41ff8c30 100644 --- a/include/trace/events/tcp.h +++ b/include/trace/events/tcp.h @@ -259,6 +259,12 @@ TRACE_EVENT(tcp_retransmit_synack, __entry->saddr_v6, __entry->daddr_v6) ); +DECLARE_TRACE(tcp_cwnd_reduction_tp, + TP_PROTO(const struct sock *sk, int newly_acked_sacked, + int newly_lost, int flag), + TP_ARGS(sk, newly_acked_sacked, newly_lost, flag) +); + #include TRACE_EVENT(tcp_probe, diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 074406890552a..fbb67a098543b 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2709,6 +2709,8 @@ void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int newly_lost, if (newly_acked_sacked <= 0 || WARN_ON_ONCE(!tp->prior_cwnd)) return; + trace_tcp_cwnd_reduction_tp(sk, newly_acked_sacked, newly_lost, flag); + tp->prr_delivered += newly_acked_sacked; if (delta < 0) { u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered +