Status changed to 'Confirmed' because the bug affects multiple users.
** Changed in: linux-signed-lowlatency-hwe-6.5 (Ubuntu)
Status: New => Confirmed
--
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux-signed-lowlatency-hwe-6.5 in
Ubuntu.
https://bugs.launchpad.net/bugs/2051733
Title:
Specifying nohz_full disables CPU frequency scaling
Status in linux-signed-lowlatency-hwe-6.5 package in Ubuntu:
Confirmed
Bug description:
With the lowlatency kernel, if I specify "nohz_full=1-15" boot
parameter then CPU frequency scaling doesn't work for the logical
cores 1-15. That is, only logical core 0 shows varying CPU frequency
in its /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq file, all
other cores constantly show 800000 in their scaling_cur_freq files
(which is the lowest supported frequency) regardless of the CPU load.
Steps to reproduce:
1. Add "nohz_full=1-15" (specify the core numbers to include all logical
cores except 0) to kernel boot options in /etc/default/grub.
2. Run `sudo update-grub` and reboot.
3. Upon booting, run a multithreaded workload. For example, run `openssl
speed -multi $(nproc --all)`.
4. In another console, monitor CPU frequencies by running `watch cat
/sys/devices/system/cpu/cpu[0-9]*/cpufreq/scaling_cur_freq`.
Actual results:
All cores specified in "nohz_full" parameter are always at their
lowest frequency.
Expected results:
All cores must scale the frequency up with active load.
ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: linux-image-6.5.0-15-lowlatency 6.5.0-15.15.1.1~22.04.1
ProcVersionSignature: Ubuntu 6.5.0-15.15.1.1~22.04.1-lowlatency 6.5.3
Uname: Linux 6.5.0-15-lowlatency x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu82.5
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Tue Jan 30 23:39:51 2024
InstallationDate: Installed on 2015-05-01 (3196 days ago)
InstallationMedia: Kubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
SourcePackage: linux-signed-lowlatency-hwe-6.5
UpgradeStatus: Upgraded to jammy on 2022-05-14 (626 days ago)
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux-signed-lowlatency-hwe-6.5/+bug/2051733/+subscriptions
--
Mailing list: https://launchpad.net/~kernel-packages
Post to : [email protected]
Unsubscribe : https://launchpad.net/~kernel-packages
More help : https://help.launchpad.net/ListHelp
