Public bug reported: === SUMMARY === Realtek RTL8125B 2.5GbE NIC performance degrades from 2.3 Gbps to 800-1100 Mbps over 5-7 days of uptime on Ubuntu 25.10. Issue NOT present on Ubuntu 24.04 LTS.
=== IMPACT === - Affects common consumer motherboards (ASRock, ASUS, MSI, Gigabyte) - Users with 2.5G+ internet see 50-80% speed loss - Reboot temporarily restores speed === EXPECTED === - Sustained 2.3+ Gbps throughput - Stable performance over weeks/months === ACTUAL === - After reboot: 2276 Mbps down - After 13 hours: 266 Mbps down (78% loss) - After 7 days: 1100 Mbps down (52% loss) === ROOT CAUSE === Kernel 6.17.x changed two defaults: 1. GRO (Generic Receive Offload) disabled for Realtek NICs 2. Network buffers too small (2.6 MB vs 134 MB needed) Both worked correctly in Ubuntu 24.04 LTS (kernel 6.8.x) - this is a REGRESSION. === WORKAROUND (CONFIRMED) === sudo ethtool -K enp4s0 gro on sudo sysctl -w net.core.rmem_max=134217728 sudo sysctl -w net.core.netdev_max_backlog=5000 Result: Sustained 2.2 Gbps vs 800 Mbps degraded === HARDWARE === - Motherboard: ASRock B760 Pro RS/D4 WiFi - NIC: Realtek RTL8125B rev 05 - Driver: r8125-dkms 9.016.01-NAPI === REPRODUCTION === 1. Ubuntu 25.10 + Realtek RTL8125 + 2.5G internet 2. Speed test after boot: 2.3 Gbps 3. Speed test after 12-24 hours: 800-1100 Mbps 4. Reboot restores speed (temporary) === DETAILED ANALYSIS === Full technical details with performance data posted to driver maintainer: https://github.com/awesometic/realtek-r8125-dkms/issues/90 === FIX REQUESTED === 1. Re-enable GRO by default for Realtek 8125 2. Restore buffer defaults to kernel 6.8.x values 3. Backport to Ubuntu 25.10 stable updates ProblemType: Bug DistroRelease: Ubuntu 25.10 Package: linux-image-6.17.0-12-generic 6.17.0-12.12 ProcVersionSignature: Ubuntu 6.17.0-12.12-generic 6.17.2 Uname: Linux 6.17.0-12-generic x86_64 ApportVersion: 2.33.1-0ubuntu3 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: will 18670 F.... wireplumber /dev/snd/seq: will 18653 F.... pipewire CasperMD5CheckResult: pass CurrentDesktop: ubuntu:GNOME Date: Sat Jan 31 13:42:12 2026 InstallationDate: Installed on 2025-04-22 (285 days ago) InstallationMedia: Ubuntu 25.04 "Plucky Puffin" - Release amd64 (20250415.3) IwDevWlp0s20f3Link: Not connected. MachineType: ASRock B760 Pro RS/D4 WiFi ProcEnviron: LANG=en_US.UTF-8 PATH=(custom, no user) SHELL=/bin/bash TERM=xterm-256color XDG_RUNTIME_DIR=<set> ProcFB: 0 i915drmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.17.0-12-generic root=UUID=1d55f811-23da-48b3-b52a-1624068339a9 ro quiet splash crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M vt.handoff=7 RelatedPackageVersions: firmware-sof N/A linux-firmware 20250901.git993ff19b-0ubuntu1.6 SourcePackage: linux UpgradeStatus: Upgraded to questing on 2025-12-15 (47 days ago) dmi.bios.date: 09/25/2025 dmi.bios.release: 5.27 dmi.bios.vendor: American Megatrends International, LLC. dmi.bios.version: 9.01 dmi.board.name: B760 Pro RS/D4 WiFi dmi.board.vendor: ASRock dmi.chassis.asset.tag: To Be Filled By O.E.M. dmi.chassis.type: 3 dmi.chassis.vendor: To Be Filled By O.E.M. dmi.chassis.version: To Be Filled By O.E.M. dmi.modalias: dmi:bvnAmericanMegatrendsInternational,LLC.:bvr9.01:bd09/25/2025:br5.27:svnASRock:pnB760ProRS/D4WiFi:pvrToBeFilledByO.E.M.:rvnASRock:rnB760ProRS/D4WiFi:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:skuToBeFilledByO.E.M.: dmi.product.family: To Be Filled By O.E.M. dmi.product.name: B760 Pro RS/D4 WiFi dmi.product.sku: To Be Filled By O.E.M. dmi.product.version: To Be Filled By O.E.M. dmi.sys.vendor: ASRock ** Affects: linux (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug questing wayland-session -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2139510 Title: Network performance degradation with Realtek RTL8125B on kernel 6.17.x To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2139510/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
