transport_latency.bt

#!/usr/bin/env bpftrace
// SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
// SPDX-License-Identifier: Apache-2.0
//
// Socket read/write latencies (transport-agnostic: traces sendmsg/recvmsg).
// Works for both TCP and NATS since both go through kernel sockets.
//
// Usage: sudo bpftrace transport_latency.bt
//        sudo bpftrace -p <PID> transport_latency.bt

tracepoint:syscalls:sys_enter_sendmsg,
tracepoint:syscalls:sys_enter_sendto,
tracepoint:syscalls:sys_enter_write
/comm == "tokio-runtime-w" || comm == "dynamo-frontend"/
{
    @send_start[tid] = nsecs;
}

tracepoint:syscalls:sys_exit_sendmsg,
tracepoint:syscalls:sys_exit_sendto,
tracepoint:syscalls:sys_exit_write
/@send_start[tid]/
{
    $delta = nsecs - @send_start[tid];
    @send_latency_us = hist($delta / 1000);
    delete(@send_start[tid]);
}

tracepoint:syscalls:sys_enter_recvmsg,
tracepoint:syscalls:sys_enter_recvfrom,
tracepoint:syscalls:sys_enter_read
/comm == "tokio-runtime-w" || comm == "dynamo-frontend"/
{
    @recv_start[tid] = nsecs;
}

tracepoint:syscalls:sys_exit_recvmsg,
tracepoint:syscalls:sys_exit_recvfrom,
tracepoint:syscalls:sys_exit_read
/@recv_start[tid]/
{
    $delta = nsecs - @recv_start[tid];
    @recv_latency_us = hist($delta / 1000);
    delete(@recv_start[tid]);
}

interval:s:5
{
    printf("\n--- Send Latency (us) ---\n");
    print(@send_latency_us);
    printf("\n--- Recv Latency (us) ---\n");
    print(@recv_latency_us);
    clear(@send_latency_us);
    clear(@recv_latency_us);
}

END
{
    clear(@send_start);
    clear(@recv_start);
}