I confirm your findings. In my case I am using: The intel_pstate CPU frequency scaling driver; powersave CPU frequency scaling governor; HWP, HardWare Pstate, control is disabled; A mainline kernel, 6.8-rc1, compiled with the kernel configuration changes being considered in that other bug report. My main test server with Ubuntu 20.04.6.
Note also, in my case, the CPU frequencies actually seem to be scaling properly, it is just that they are not being reported properly via "/sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq". -- 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 : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
