UDP throughput is not credible: shows 224Gbps on a host constrained by PCIe Gen3x8 (~56Gbps). TCP throughput on the same link is always spot on.

ntttcp reports tcp throughput just fine. UDP sometimes is >= 4x max throughput.

nload shows

Curr: 49.43 GBit/s
Max: 50.36 GBit/s

while ntttcp reports 224.59Gbps simultaneously.

ssh @ ntttcp -s 192.168.100.1 -t 60 -W 2 -C 2 -u --show-nic-packets enp24s0f0 --show-dev-interrupts mlx5_0 -O ntttcp.enp24s0f0.2021-01-22T17:06:10-0600

• ntttcp -r -t 60 -W 2 -C 2 -u --show-nic-packets enp24s0f0 --show-dev-interrupts mlx5_0 -O ntttcp.enp24s0f0.2021-01-22T17:06:10-0600
  NTTTCP for Linux 1.4.0

17:06:13 INFO: the UDP send size is too big. use the max value
17:06:13 INFO: 17 threads created
NTTTCP for Linux 1.4.0

17:09:18 INFO: the UDP send size is too big. use the max value
17:06:13 INFO: Test cycle time negotiated is: 64 seconds
17:09:18 INFO: Test cycle time negotiated is: 64 seconds
17:09:18 INFO: 64 threads created
17:06:13 INFO: Network activity progressing...
17:09:18 INFO: 64 connections created in 11400 microseconds
17:09:18 INFO: Network activity progressing...
Real-time throughput: 224.59Gbps
Real-time throughput: 3.88Gbps
Real-time throughput: 220.25Gbps
Real-time throughput: 4.79Gbps
Real-time throughput: 212.56Gbps
Real-time throughput: 5.78Gbps
Real-time throughput: 211.80Gbps
17:09:20 INFO: Test warmup completed.
Real-time throughput: 14.03Gbps
17:06:15 INFO: Test warmup completed.
Real-time throughput: 14.66Gbps
Real-time throughput: 211.70Gbps
Real-time throughput: 13.00Gbps
Real-time throughput: 211.11Gbps
Real-time throughput: 13.66Gbps
Real-time throughput: 212.03Gbps
Real-time throughput: 13.76Gbps
Real-time throughput: 211.90Gbps
Real-time throughput: 12.55Gbps
Real-time throughput: 211.42Gbps
Real-time throughput: 13.34Gbps
Real-time throughput: 212.46Gbps
Real-time throughput: 14.92Gbps
Real-time throughput: 212.47Gbps
Real-time throughput: 10.97Gbps
Real-time throughput: 211.27Gbps
Real-time throughput: 13.45Gbps
Real-time throughput: 212.22Gbps
Real-time throughput: 13.25Gbps
Real-time throughput: 211.98Gbps
Real-time throughput: 14.44Gbps
Real-time throughput: 211.84Gbps
Real-time throughput: 12.64Gbps
Real-time throughput: 211.77Gbps
Real-time throughput: 12.38Gbps
Real-time throughput: 211.97Gbps
Real-time throughput: 12.02Gbps
Real-time throughput: 211.69Gbps
Real-time throughput: 10.27Gbps
Real-time throughput: 211.42Gbps
Real-time throughput: 10.74Gbps
Real-time throughput: 210.76Gbps
Real-time throughput: 13.98Gbps
Real-time throughput: 212.06Gbps
Real-time throughput: 15.31Gbps
Real-time throughput: 212.02Gbps
Real-time throughput: 14.34Gbps
Real-time throughput: 212.02Gbps
Real-time throughput: 15.50Gbps
Real-time throughput: 210.64Gbps
Real-time throughput: 10.82Gbps
Real-time throughput: 211.07Gbps
Real-time throughput: 9.45Gbps
Real-time throughput: 212.18Gbps
Real-time throughput: 12.33Gbps
Real-time throughput: 212.24Gbps
Real-time throughput: 15.33Gbps
Real-time throughput: 209.95Gbps
Real-time throughput: 11.81Gbps
Real-time throughput: 211.70Gbps
Real-time throughput: 14.93Gbps
Real-time throughput: 212.42Gbps
Real-time throughput: 12.86Gbps
Real-time throughput: 211.48Gbps
Real-time throughput: 12.88Gbps
Real-time throughput: 209.77Gbps
Real-time throughput: 12.73Gbps
Real-time throughput: 210.95Gbps
Real-time throughput: 11.34Gbps
Real-time throughput: 211.52Gbps
Real-time throughput: 9.82Gbps
Real-time throughput: 212.21Gbps
Real-time throughput: 13.47Gbps
Real-time throughput: 210.27Gbps
Real-time throughput: 12.01Gbps
Real-time throughput: 211.72Gbps
Real-time throughput: 13.58Gbps
Real-time throughput: 212.00Gbps
Real-time throughput: 16.84Gbps
Real-time throughput: 210.88Gbps
Real-time throughput: 14.13Gbps
Real-time throughput: 210.31Gbps
Real-time throughput: 10.85Gbps
Real-time throughput: 211.57Gbps
Real-time throughput: 13.40Gbps
Real-time throughput: 212.02Gbps
Real-time throughput: 10.63Gbps
Real-time throughput: 211.19Gbps
Real-time throughput: 15.06Gbps
Real-time throughput: 211.32Gbps
Real-time throughput: 16.16Gbps
Real-time throughput: 211.58Gbps
Real-time throughput: 12.64Gbps
Real-time throughput: 212.02Gbps
Real-time throughput: 13.56Gbps
Real-time throughput: 210.69Gbps
Real-time throughput: 10.34Gbps
Real-time throughput: 211.79Gbps
Real-time throughput: 11.16Gbps
Real-time throughput: 211.23Gbps
Real-time throughput: 14.99Gbps
Real-time throughput: 212.00Gbps
Real-time throughput: 13.03Gbps
Real-time throughput: 209.73Gbps
Real-time throughput: 12.87Gbps
Real-time throughput: 212.41Gbps
Real-time throughput: 14.36Gbps
Real-time throughput: 212.22Gbps
Real-time throughput: 14.59Gbps
Real-time throughput: 211.84Gbps
Real-time throughput: 13.82Gbps
Real-time throughput: 209.68Gbps
Real-time throughput: 13.38Gbps
Real-time throughput: 210.55Gbps
Real-time throughput: 15.46Gbps
Real-time throughput: 211.65Gbps
Real-time throughput: 13.07Gbps
Real-time throughput: 211.94Gbps
Real-time throughput: 18.01Gbps
Real-time throughput: 210.38Gbps
Real-time throughput: 16.14Gbps
Real-time throughput: 210.69Gbps
Real-time throughput: 11.06Gbps
Real-time throughput: 211.91Gbps
Real-time throughput: 12.12Gbps
Real-time throughput: 210.89Gbps
Real-time throughput: 13.91Gbps
Real-time throughput: 209.28Gbps
Real-time throughput: 12.82Gbps
Real-time throughput: 210.86Gbps
Real-time throughput: 13.93Gbps
Real-time throughput: 210.79Gbps
Real-time throughput: 15.03Gbps
Real-time throughput: 210.89Gbps
Real-time throughput: 15.58Gbps
Real-time throughput: 210.79Gbps
Real-time throughput: 8.64Gbps
Real-time throughput: 211.63Gbps
Real-time throughput: 9.77Gbps
Real-time throughput: 210.34Gbps
Real-time throughput: 12.94Gbps
Real-time throughput: 210.76Gbps
Real-time throughput: 14.53Gbps
Real-time throughput: 211.00Gbps
Real-time throughput: 13.62Gbps
Real-time throughput: 211.46Gbps
Real-time throughput: 9.33Gbps
Real-time throughput: 210.83Gbps
Real-time throughput: 13.55Gbps
Real-time throughput: 210.12Gbps
Real-time throughput: 13.32Gbps
Real-time throughput: 210.33Gbps
Real-time throughput: 11.53Gbps
Real-time throughput: 210.46Gbps
Real-time throughput: 11.87Gbps
Real-time throughput: 211.90Gbps
Real-time throughput: 13.31Gbps
Real-time throughput: 209.85Gbps
Real-time throughput: 13.80Gbps
Real-time throughput: 211.07Gbps
Real-time throughput: 13.50Gbps
Real-time throughput: 211.90Gbps
Real-time throughput: 12.51Gbps
Real-time throughput: 211.89Gbps
Real-time throughput: 16.05Gbps
Real-time throughput: 210.71Gbps
Real-time throughput: 11.61Gbps
Real-time throughput: 212.42Gbps
Real-time throughput: 12.37Gbps
Real-time throughput: 210.53Gbps
Real-time throughput: 11.23Gbps
Real-time throughput: 211.46Gbps
Real-time throughput: 12.38Gbps
Real-time throughput: 209.61Gbps
Real-time throughput: 14.87Gbps
Real-time throughput: 210.24Gbps
Real-time throughput: 10.98Gbps
Real-time throughput: 210.25Gbps
Real-time throughput: 14.29Gbps
Real-time throughput: 209.46Gbps
Real-time throughput: 15.74Gbps
Real-time throughput: 209.34Gbps
Real-time throughput: 12.05Gbps
Real-time throughput: 210.47Gbps
Real-time throughput: 12.75Gbps
Real-time throughput: 210.93Gbps
Real-time throughput: 13.16Gbps
Real-time throughput: 210.22Gbps
Real-time throughput: 12.84Gbps
Real-time throughput: 209.33Gbps
Real-time throughput: 17.58Gbps
Real-time throughput: 210.90Gbps
Real-time throughput: 13.08Gbps
Real-time throughput: 209.22Gbps
Real-time throughput: 13.31Gbps
Real-time throughput: 208.82Gbps
Real-time throughput: 12.14Gbps
Real-time throughput: 208.85Gbps
Real-time throughput: 15.88Gbps
Real-time throughput: 209.82Gbps
Real-time throughput: 14.67Gbps
Real-time throughput: 210.51Gbps
Real-time throughput: 12.32Gbps
Real-time throughput: 208.36Gbps
Real-time throughput: 14.17Gbps
Real-time throughput: 209.58Gbps
Real-time throughput: 15.51Gbps
Real-time throughput: 209.66Gbps
Real-time throughput: 9.86Gbps
Real-time throughput: 209.85Gbps
Real-time throughput: 13.42Gbps
Real-time throughput: 207.84Gbps
Real-time throughput: 14.68Gbps
Real-time throughput: 210.13Gbps
Real-time throughput: 14.73Gbps
Real-time throughput: 209.80Gbps
Real-time throughput: 14.83Gbps
Real-time throughput: 210.57Gbps
Real-time throughput: 17.17Gbps
Real-time throughput: 208.10Gbps
Real-time throughput: 14.25Gbps
Real-time throughput: 209.61Gbps
Real-time throughput: 11.85Gbps
Real-time throughput: 208.79Gbps
Real-time throughput: 14.92Gbps
17:07:15 INFO: Test run completed.
17:07:15 INFO: Test cooldown is in progress...
Real-time throughput: 210.36Gbps
17:10:20 INFO: Test run completed.
17:10:20 INFO: Test cooldown is in progress...
17:07:17 INFO: Test cycle finished.
17:07:17 INFO: ##### Totals: #####
17:07:17 INFO: test duration :60.35 seconds
17:07:17 INFO: total bytes :100200489805
17:07:17 INFO: throughput :13.28Gbps
17:07:17 INFO: total packets:
17:07:17 INFO: tx_packets :9
17:07:17 INFO: rx_packets :45032701
17:07:17 INFO: interrupts:
17:07:17 INFO: total :0
17:07:17 INFO: pkts/interrupt :0.00
17:10:22 INFO: Test cycle finished.
17:07:17 INFO: cpu cores :48
17:07:17 INFO: cpu speed :3899.804MHz
17:07:17 INFO: user :0.11%
17:07:17 INFO: system :0.73%
17:07:17 INFO: idle :98.13%
17:07:17 INFO: iowait :0.00%
17:07:17 INFO: softirq :1.03%
17:07:17 INFO: cycles/byte :2.11
17:07:17 INFO: cpu busy (all) :40.20%

17:10:22 INFO: receiver exited from current test
17:10:22 INFO: 64 connections tested
17:10:22 INFO: ##### Totals: #####
17:10:22 INFO: test duration :60.59 seconds
17:10:22 INFO: total bytes :1597111689953
17:10:22 INFO: throughput :210.89Gbps
17:10:22 INFO: total packets:
17:10:22 INFO: tx_packets :45191247
17:10:22 INFO: rx_packets :9
17:10:22 INFO: interrupts:
17:10:22 INFO: total :0
17:10:22 INFO: pkts/interrupt :0.00
17:10:22 INFO: cpu cores :80
17:10:22 INFO: cpu speed :2501.000MHz
17:10:22 INFO: user :0.37%
17:10:22 INFO: system :71.94%
17:10:22 INFO: idle :18.23%
17:10:22 INFO: iowait :0.00%
17:10:22 INFO: softirq :9.46%
17:10:22 INFO: cycles/byte :6.21
17:10:22 INFO: cpu busy (all) :6373.12%

Start by reproducing the UDP command in the issue and compare ntttcp's sender and receiver totals, packet counters, and real-time values with nload on the same link. No source files or tests are named; done means identifying why UDP reports impossible throughput and ensuring the reported value agrees with the link capacity and independent measurements.