[Bug 276760] vtnet driver incorrectly calculates checksums
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Date: Thu, 16 Oct 2025 16:19:49 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=276760
--- Comment #30 from vova@fbsd.ru ---
(In reply to Michael Tuexen from comment #29)
hm ... good question, I've created a new VM and did series of tests:
CPX22 (2 vCPU 4GB RAM, old CX11 is not available any more)
IPv4, Nuremberg
just install 14.3, upgrade to 14.3p4 (with freebsd-update), install
speedtest-go package, copy stable/14-087fc6ae0a8c kernel build outside as
alternative
summarized results:
FreeBSD Offloading Try Download Upload
Mbps Mbps
14.3p4 yes 1 1,413 736
14.3p4 yes 2 1,348 833
14.3p4 yes 3 1,377 901
14.3p4 yes 4 1,357 737
14.3p4 yes 5 1,352 571
14.3p4 yes 6 1,247 776
14.3p4 yes avg 1,349 759
CV% 4.11% 14.71%
14.3p4 no 1 1,574 681
14.3p4 no 2 1,598 702
14.3p4 no 3 1,237 602
14.3p4 no 4 1,537 778
14.3p4 no 5 1,541 745
14.3p4 no 6 1,568 623
14.3p4 no avg 1,509 688
CV% 8.96% 9.90%
14-087fc6ae0a8c yes 1 1,210 675
14-087fc6ae0a8c yes 2 1,332 707
14-087fc6ae0a8c yes 3 1,684 703
14-087fc6ae0a8c yes 4 1,320 460
14-087fc6ae0a8c yes 5 1,333 694
14-087fc6ae0a8c yes 6 1,279 825
14-087fc6ae0a8c yes avg 1,360 677
CV% 12.18% 17.58%
14-087fc6ae0a8c no 1 1,466 807
14-087fc6ae0a8c no 2 1,213 751
14-087fc6ae0a8c no 3 1,527 678
14-087fc6ae0a8c no 4 1,825 1,037
14-087fc6ae0a8c no 5 1,185 1,064
14-087fc6ae0a8c no 6 1,230 1,086
14-087fc6ae0a8c no avg 1,408 904
CV% 17.71% 19.81%
What is seen:
1. diviations/variations is quite high, so, clearely does not worth to trust
data after one measurement (my bad)
2. still incomparable with yours 260 Mbps (both up and down) - we masure
something different?
3. turning off TSOs add ~10-12% of download consistently, but for upload ->
sometimes improves, sometimes not
(ifconfig vtnet0 -tso4 -tso6 -lro -rxcsum)
4. and these results still did not match what I have in my production VM
(will re-test with multiple measurements)
# sysctl dev.vtnet.0
dev.vtnet.0.txq0.rescheduled: 0
dev.vtnet.0.txq0.tso: 1388393
dev.vtnet.0.txq0.csum: 20810001
dev.vtnet.0.txq0.omcasts: 0
dev.vtnet.0.txq0.obytes: 18916415358
dev.vtnet.0.txq0.opackets: 20810007
dev.vtnet.0.rxq0.rescheduled: 0
dev.vtnet.0.rxq0.host_lro: 216036
dev.vtnet.0.rxq0.csum_failed: 0
dev.vtnet.0.rxq0.csum: 17119906
dev.vtnet.0.rxq0.ierrors: 0
dev.vtnet.0.rxq0.iqdrops: 0
dev.vtnet.0.rxq0.ibytes: 36642213337
dev.vtnet.0.rxq0.ipackets: 24902539
dev.vtnet.0.tx_task_rescheduled: 0
dev.vtnet.0.tx_tso_offloaded: 0
dev.vtnet.0.tx_csum_offloaded: 0
dev.vtnet.0.tx_defrag_failed: 0
dev.vtnet.0.tx_defragged: 0
dev.vtnet.0.tx_tso_without_csum: 0
dev.vtnet.0.tx_tso_not_tcp: 0
dev.vtnet.0.tx_csum_proto_mismatch: 0
dev.vtnet.0.tx_csum_unknown_ethtype: 0
dev.vtnet.0.rx_task_rescheduled: 0
dev.vtnet.0.rx_csum_offloaded: 0
dev.vtnet.0.rx_csum_failed: 0
dev.vtnet.0.rx_csum_bad_proto: 0
dev.vtnet.0.rx_csum_bad_offset: 0
dev.vtnet.0.rx_csum_bad_ipproto: 0
dev.vtnet.0.rx_csum_bad_ethtype: 0
dev.vtnet.0.rx_mergeable_failed: 0
dev.vtnet.0.rx_enq_replacement_failed: 0
dev.vtnet.0.rx_frame_too_large: 0
dev.vtnet.0.mbuf_alloc_failed: 0
dev.vtnet.0.act_vq_pairs: 1
dev.vtnet.0.req_vq_pairs: 1
dev.vtnet.0.max_vq_pairs: 1
dev.vtnet.0.%iommu:
dev.vtnet.0.%parent: virtio_pci1
dev.vtnet.0.%pnpinfo: vendor=0x00001af4 device=0x1041 subvendor=0x1af4
device_type=0x00000001
dev.vtnet.0.%location:
dev.vtnet.0.%driver: vtnet
dev.vtnet.0.%desc: VirtIO Networking Adapter
# sysctl hw.vtnet
hw.vtnet.lro_mbufq_depth: 0
hw.vtnet.lro_entry_count: 128
hw.vtnet.rx_process_limit: 1024
hw.vtnet.tso_maxlen: 65535
hw.vtnet.mq_max_pairs: 32
hw.vtnet.mq_disable: 0
hw.vtnet.lro_disable: 1
hw.vtnet.tso_disable: 0
hw.vtnet.fixup_needs_csum: 0
hw.vtnet.csum_disable: 0
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