Since the 5.10 kernel (eg Bullseye) and above, there has been an issue with excessive network latency with the Debian RT kernel and Realtek network interfaces with Mesa ethernet cards. When it bites, it causes a hm2_eth "error finishing read" and disables the mesa card. By avoiding realtek NIC's a whole swathe of small portable industrial PC's can no longer be used with linuxcnc. A resolution for this issue needs to be found before 2.9 rolls out or there will be massive support issues.
This issue is restricted to the debian environment. Installing a compiled kernel or running on a non-debian distribution solves the issue (I tried arch-linux) By default Debian uses the r8169 network driver for all realtek NIC's but provides a r8168-dkms driver which should solve the issue if installed if supported hardware is present. However, it appears that when this is installed, the network latency is rarely resolved. I suspect it is because of a buggy driver in Debian. Some people (PCW, JT et al) have resorted to compiling the kernel from pristine sources. I have finally been able to compile a 6.1 version of the PREEMPT_RT kernel and headers which I have stored in Google Drive https://drive.google.com/drive/folders/10uwGg5RvZDDlLtQ8BZhM3At_gODk16na?usp=sharing By installing the headers, the image, the R8168-dkms driver followed by setting isolcpus=2,3, the issue seems to be resolved on my J1900 hardware but more testing is required. Refer this forum thread https://forum.linuxcnc.org/27-driver-boards/46911-mesa-hm2-hm2-7i96s-0-error-finishing-read?start=190#259341 Its my recommendation that the 2.9 iso installer includes a custom kernel similar to what I've built. Consideration should also be given to deploying a custom kernel with the Debian package now on bookworm. Of course a better solution would be to get the Debian kernel developers to fix their buggy implementation of the linux kernel and the realtek network drivers. I have previously reported this issue as a bug on Debian. It might be helpful if others could add their feedback to the issue https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1022170 Rod Webster VMN® www.vmn.com.au Ph: 1300 896 832 Mob: +61 435 765 611 _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
