A manual test on riccioli didn't managed to reproduce this issue: $ sudo ./udpgso_bench.sh ipv4 tcp tcp tx: 10737 MB/s 182123 calls/s 182123 msg/s tcp rx: 10748 MB/s 182189 calls/s tcp tx: 10759 MB/s 182487 calls/s 182487 msg/s tcp rx: 10771 MB/s 182608 calls/s tcp tx: 10632 MB/s 180335 calls/s 180335 msg/s tcp zerocopy tcp tx: 7447 MB/s 126308 calls/s 126308 msg/s tcp rx: 7454 MB/s 124602 calls/s tcp tx: 7500 MB/s 127209 calls/s 127209 msg/s tcp rx: 7502 MB/s 122880 calls/s tcp tx: 8538 MB/s 144818 calls/s 144818 msg/s udp udp rx: 1007 MB/s 718031 calls/s udp tx: 1010 MB/s 719586 calls/s 17133 msg/s udp rx: 980 MB/s 698532 calls/s udp tx: 979 MB/s 697746 calls/s 16613 msg/s udp rx: 998 MB/s 711266 calls/s udp tx: 997 MB/s 710514 calls/s 16917 msg/s udp gso udp rx: 2507 MB/s 1786348 calls/s udp tx: 2519 MB/s 42736 calls/s 42736 msg/s udp rx: 2489 MB/s 1773492 calls/s udp tx: 2487 MB/s 42182 calls/s 42182 msg/s udp rx: 2563 MB/s 1826286 calls/s udp tx: 2557 MB/s 43385 calls/s 43385 msg/s udp gso zerocopy udp rx: 1862 MB/s 1326738 calls/s udp tx: 1870 MB/s 31724 calls/s 31724 msg/s udp rx: 1859 MB/s 1324960 calls/s udp tx: 1857 MB/s 31509 calls/s 31509 msg/s udp rx: 1852 MB/s 1319654 calls/s udp tx: 1850 MB/s 31388 calls/s 31388 msg/s udp gso timestamp udp rx: 2460 MB/s 1752450 calls/s udp tx: 2470 MB/s 41899 calls/s 41899 msg/s udp rx: 2477 MB/s 1764504 calls/s udp tx: 2474 MB/s 41970 calls/s 41970 msg/s udp rx: 2490 MB/s 1773912 calls/s udp tx: 2487 MB/s 42193 calls/s 42193 msg/s udp gso zerocopy audit udp rx: 1698 MB/s 1209890 calls/s udp tx: 1708 MB/s 28974 calls/s 28974 msg/s udp rx: 1771 MB/s 1262257 calls/s udp tx: 1769 MB/s 30018 calls/s 30018 msg/s udp rx: 1720 MB/s 1225487 calls/s udp tx: 1718 MB/s 29151 calls/s 29151 msg/s Summary over 3.000 seconds... sum udp tx: 1773 MB/s 88143 calls (29381/s) 88143 msgs (29381/s) Zerocopy acks: 88143 udp gso timestamp audit udp rx: 2436 MB/s 1735314 calls/s udp tx: 2446 MB/s 41492 calls/s 41492 msg/s udp rx: 2474 MB/s 1762446 calls/s udp tx: 2471 MB/s 41917 calls/s 41917 msg/s udp rx: 2448 MB/s 1743966 calls/s udp tx: 2444 MB/s 41455 calls/s 41455 msg/s Summary over 3.000 seconds... sum udp tx: 2512 MB/s 124864 calls (41621/s) 124864 msgs (41621/s) Tx Timestamps: 124864 received 0 errors udp gso zerocopy timestamp audit udp rx: 1630 MB/s 1161141 calls/s udp tx: 1636 MB/s 27759 calls/s 27759 msg/s udp rx: 1575 MB/s 1121959 calls/s udp tx: 1573 MB/s 26685 calls/s 26685 msg/s udp rx: 1571 MB/s 1119487 calls/s udp tx: 1568 MB/s 26601 calls/s 26601 msg/s Summary over 3.000 seconds... sum udp tx: 1631 MB/s 81045 calls (27015/s) 81045 msgs (27015/s) Tx Timestamps: 81045 received 0 errors Zerocopy acks: 81045 ipv6 tcp tcp tx: 9236 MB/s 156655 calls/s 156655 msg/s tcp rx: 9246 MB/s 156687 calls/s tcp tx: 9857 MB/s 167192 calls/s 167192 msg/s tcp rx: 9867 MB/s 167279 calls/s tcp tx: 9618 MB/s 163129 calls/s 163129 msg/s tcp zerocopy tcp tx: 7886 MB/s 133763 calls/s 133763 msg/s tcp rx: 7893 MB/s 109473 calls/s tcp tx: 7948 MB/s 134820 calls/s 134820 msg/s tcp rx: 7957 MB/s 111157 calls/s tcp tx: 8289 MB/s 140597 calls/s 140597 msg/s udp udp rx: 932 MB/s 680171 calls/s udp tx: 935 MB/s 682367 calls/s 15869 msg/s udp rx: 939 MB/s 684939 calls/s udp tx: 937 MB/s 683442 calls/s 15894 msg/s udp rx: 943 MB/s 687784 calls/s udp tx: 943 MB/s 687828 calls/s 15996 msg/s udp gso udp rx: 2570 MB/s 1874499 calls/s udp tx: 2578 MB/s 43731 calls/s 43731 msg/s udp rx: 2479 MB/s 1808214 calls/s udp tx: 2476 MB/s 42006 calls/s 42006 msg/s udp rx: 2466 MB/s 1798991 calls/s udp tx: 2463 MB/s 41791 calls/s 41791 msg/s udp gso zerocopy udp rx: 1600 MB/s 1167590 calls/s udp tx: 1605 MB/s 27237 calls/s 27237 msg/s udp rx: 1566 MB/s 1142307 calls/s udp tx: 1565 MB/s 26547 calls/s 26547 msg/s udp rx: 1648 MB/s 1202208 calls/s udp tx: 1646 MB/s 27929 calls/s 27929 msg/s udp gso timestamp udp rx: 2378 MB/s 1734569 calls/s udp tx: 2390 MB/s 40550 calls/s 40550 msg/s udp rx: 2386 MB/s 1740167 calls/s udp tx: 2383 MB/s 40428 calls/s 40428 msg/s udp rx: 2404 MB/s 1753411 calls/s udp tx: 2401 MB/s 40735 calls/s 40735 msg/s udp gso zerocopy audit udp rx: 1579 MB/s 1152018 calls/s udp tx: 1586 MB/s 26904 calls/s 26904 msg/s udp rx: 1574 MB/s 1148512 calls/s udp tx: 1572 MB/s 26678 calls/s 26678 msg/s udp rx: 1671 MB/s 1218910 calls/s udp tx: 1668 MB/s 28306 calls/s 28306 msg/s Summary over 3.000 seconds... sum udp tx: 1647 MB/s 81888 calls (27296/s) 81888 msgs (27296/s) Zerocopy acks: 81888 udp gso timestamp audit udp rx: 2457 MB/s 1792369 calls/s udp tx: 2465 MB/s 41816 calls/s 41816 msg/s udp rx: 2464 MB/s 1797099 calls/s udp tx: 2461 MB/s 41749 calls/s 41749 msg/s udp rx: 2393 MB/s 1745777 calls/s udp tx: 2391 MB/s 40558 calls/s 40558 msg/s Summary over 3.000 seconds... sum udp tx: 2497 MB/s 124123 calls (41374/s) 124123 msgs (41374/s) Tx Timestamps: 124123 received 0 errors udp gso zerocopy timestamp audit udp rx: 1584 MB/s 1155782 calls/s udp tx: 1589 MB/s 26964 calls/s 26964 msg/s udp rx: 1574 MB/s 1147947 calls/s udp tx: 1571 MB/s 26661 calls/s 26661 msg/s udp rx: 1507 MB/s 1099533 calls/s udp tx: 1506 MB/s 25550 calls/s 25550 msg/s Summary over 3.000 seconds... sum udp tx: 1593 MB/s 79175 calls (26391/s) 79175 msgs (26391/s) Tx Timestamps: 79175 received 0 errors Zerocopy acks: 79175 udpgso_bench.sh: PASS=18 SKIP=0 FAIL=0 udpgso_bench.sh: PASS $ uname -a Linux riccioli 5.8.0-51-generic #57-Ubuntu SMP Wed Apr 14 16:02:45 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux And it has passed with the net test run (please find attachment for the test log) with: sudo make run_tests TARGETS=net A glitch maybe?