On 8/18/22 21:38, Joseph Salisbury wrote:
On 8/18/22 16:31, Peter Zijlstra wrote:
On Thu, Aug 18, 2022 at 03:53:28PM -0400, Joseph Salisbury wrote:
Hello,
Some Ubuntu users are using the tuned package with a 5.15.x based
real-time
kernel. Tuned adjusts various sysctl options based on a specified
profile.
This userspace package has stopped working > 5.13 due to the following
commit:
8a99b6833c88 "(sched: Move SCHED_DEBUG sysctl to debugfs)"
This commit moved some important real-time sysctl knobs to debugfs in
5.13-rc1. It also appears some of the sysctl options were not moved,
sched_min_granularity_ns, for example.
I was hoping to get some feedback on how to approach this. Would
upstream
real-time consider accepting a patch to the 5.15 real-time patch set
that
reverts this commit? Or a new patch that adds the sysctl settings
back?
Any other ideas or feedback would be appreciated!
None of those knobs were available when SCHED_DEBUG=n, so relying on
them is your error to begin with.
We have had SCHED_DEBUG=y while this kernel is in beta, so you are
correct. I need to investigate a different approach.
Secondly, real-time? Which if those values affects anything in
SCHED_FIFO/RR/DEADLINE ?
I am in the process of understanding how tuned[0] works. Many users
have reported success using tuned. One use case for tuned is to
assign isolated cores to real-time processes and then move managed
IRQs out of these isolated cores. This can be done easily with tuned
(I will research if there are other options to suggest). However,
tuned is trying to set the affected values when enabling a profile,
such as the real-time profile (Tuned offers many profiles based on a
workload type).
I will investigate further to answer your point of what in
SCHED_FIFO/RR/DEADLINE those values affect. It could be those values
are not needed at all. The dependency on them might be left over from
some need that no longer exists.
Thank you again for the feedback!
[0] https://tuned-project.org/
I also see that the github repo[0] is at version 2.19-rc1, and the
version being testing is 2.15. Many of the issues we see may already be
resolved.
I will find out how I can participate in the tuned community. At a
minimum, I can start with testing and bug fixes.
Thanks again for your feedback, Peter. And sorry for the noise.
Thanks,
Joe
[0] https://github.com/redhat-performance/tuned
