Package: r8168-dkms
Version: r8168-dkms
Severity: important
Tags: upstream newcomer
X-Debbugs-Cc: r...@vmn.com.au
Dear Maintainer,
* What led up to the situation?
We are linuxcnc users which is packaged in Bookworm. Linuxcnc requires the
PREEMPT_RT real time kernel as a prerequisite. We have found excessive latency
in the real time environment since Debian moved to the 5.x kernels. We note
that RT latency/jitter has significantly improved in the 6.x kernels and is
better again with the 6.3 kernel compiled from kernel.org sources where
latency/jitter is on a par with the 4.x kernels found in Buster.
We also note that the latency/jitter is significantly improved where a kernel
based on pristine source from kernel.org is used. We are disappointed that
Debian's implementation of the PREEMPT_RT kernel results in significantly less
performance than the upstream sources. In our recent testing, we found the 6.3
kernel gave a 265% improvement in latency/jitter over the default Debian
Bookworm 6.1.x Real time kernel. Similar improvement has also been noted
between Debian's 6.1 kernel and one we compiled from upstream source.
Network latency/jitter when we communicate point to point from a Debian PC to
an ethernet connected motion card is also another significant issue for us that
was not present in the 4.x kernels. This has not been resolved in the 6.1 to
6.3 kernels.
Linuxcnc uses a 1 ms realtime thread and we regularly see "Error Finishing
Read" reported. This error disables the connection becasue our 1 ms thread has
been overrun. This issue mainly affects Realtek NIC hardware and s of real
concern where the motion hardware could be commanding components weiging
several thousand pounds.
* What exactly did you do (or not do) that was effective (or
ineffective)?
We have found installing the R8168-dkms driver with the 6.3 kernel we compiled
has resulted a 400% improvement in network latency (from approx 800 usec)to
about 200 usec) when compared with the default R8169 kernel module driver.
We are no longer able to locate the R8168-dkms driver in the repositories,
despite it being listed as available in package search. We have downloaded a
.deb file from the Sid packages to install the correct driver.
The R8168-dkms description says to report use of the driver so the R8169 kernel
module can be updated.
* What was the outcome of this action?
A combination of the 6.3 kernel and installing the R8168-dkms driver has
resolved our issues. However, this is not something a normal user would expect
or have the skills to do.
* What outcome did you expect instead?
We expect that Debian Bookworm:
1. Has acceptible jitter/latency in a PREEMPT_RT real time environment
2. Correctly supports Realtek NIC devices covered by the R8168-dkms diver
using the default R8169 kernel module as discussed on the Realtek web site.
3. The R8168-dkms driver to continue to be made available in the Bookworm
repositories.
4. Does not negatively affect real time performance when benchamarked against
the kernel.org sources.
5. This issue may require escalation upstream.
-- System Information:
Debian Release: bookworm/sid
APT prefers testing-security
APT policy: (500, 'testing-security'), (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 6.1.0-5-rt-amd64 (SMP w/4 CPU threads; PREEMPT)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8),
LANGUAGE=en_AU:en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
