Thanks. I think I have tried most (if not all) released kernels (from 5.10 to present day 6.1) I adopted Bullseye a few weeks before it became the stable branch. Bookworm supports the Realtek R8125 NIC which I noted this week is also using the R8169 driver with the latest Bullseye kernel. I believe it is also affected by this issue but have not benchmarked it.
Linuxcnc was accepted into SID back in January 2022 and I started using the non-free sid versions from that time. I then started using Bookworm/Testing once linuxcnc was accepted into it. I have personally tested on 4-5 USFF PC's ranging from intel J1900, J4115 and i3 CPU's. All used Realtek network hardware and all were affected. All were initially using the R8169 driver. Many Other Linuxcnc users have reported the issue. All of these had hardware covered by Realteks official R8168 driver. All of these benefited from installing the Debian R8168-dkms driver. Compiling the RT kernel is not new to linuxcnc users as it was required up until Debian first released linux-image-rt packages. All we have ever needed to do was to patch the code and make a single change in menuconfig/xconfig to select the fully preemptible kernel and compile. I learnt how to build kernel debs when Bookworm was on the 6.0 kernel and built a 6.1-rt5 version which I shared publicly with other users via Google Drive. This resolved issues for a lot of users. Another user recently reported substantial improvement in latency with the 6.3 kernel so two of us built and tested it with outstanding and near identical results for both overall latency and network latency. I have not kept my .config files as PC's have been reformatted so many times. However, my kernels and the steps used to build them are available in my google drive. They will show what we have changed. Here is the link to the 6.1.0-rt5 kernel https://drive.google.com/drive/folders/1jGc6AUYKMPvsSOdWRdvhWeDX1P96tsFQ?usp=sharing <https://drive.google.com/drive/folders/1jGc6AUYKMPvsSOdWRdvhWeDX1P96tsFQ?usp=sharing> I will redo this for the final 6.1 kernel and share the config to get in step with Debian Bookworm's current state. Note we use Linuxcnc's latency testing tools to measure latency but cyclictest produces similar observable results. Unfortunately, we don't have any portable method to test network latency. Our hardware reports the maximum time to read and write to it in CPU timer ticks. This command may give some insight but the other device would need to be on a dedicated point to point ethernet connection (no hub or router) sudo chrt 99 ping -i .001 -q 10.10.10.10 I hope this covers your questions. Rod Webster VMN® www.vmn.com.au Ph: 1300 896 832 Mob: +61 435 765 611 On Sun, 23 Apr 2023 at 23:43, Ben Hutchings <b...@decadent.org.uk> wrote: > Control: retitle -1 linux-image-rt-amd64: High network latency with r8169 > driver > Control: tag -1 moreinfo > > On Sun, 2023-04-23 at 09:14 +1000, Rod Webster wrote: > > Thanks. > > That is really a disappointing response because: > > 1. Hardware selected based on Debian 4.x kernels in Buster that > operated > > safely was broken by the 5.10 and above kernels in Bullseye and Bookworm > > 2. You ask us to report a bug if the R8168-dkms package has to be used so > > we did, now no interest is shown in actioning the report > > 3. It does not address the excessive latency in the Debian RT kernel that > > is not present in the upstream version at kernel.org > > 4. It has taken a lot of work from a lot of Linuxcnc users to identify > the > > issues before this report could be made. > > > > The official ISO release of Linuxcnc is still based on Buster so not many > > users ventured into the later kernels hence the delay in reporting. > > Linuxcnc is packaged in Bookworm so the issue will be more prevalent > moving > > forward. > > > > I was told by a Debian developer involved in linuxcnc that if there were > > issues affecting us, they would be fixed. I hope something comes of this. > [...] > > I'm not dismissing this bug report, but I wanted to first make it clear > that we cannot take any responsibility for safety-critical > applications. > > As to the general issue of network latency: > - What was the latest Debian packaged kernel version you used? > - You've said that installing r8168-dkms resolves the issue. Am I > correct in assuming that when you ran the Debian packaged kernel, the > r8169 driver was used? > - Have you tested on any other machines with different network > hardware? > - We don't make a lot of changes to the kernel source, but our build > configuration will be different. Can you confirm exactly which upstream > release you've tested, and provide the configuration (.config) file you > used? > > Ben. > > -- > Ben Hutchings > It's easier to fight for one's principles than to live up to them. >
