Yes, this happens also with the mainline kernel. It also happens with the intel_cpufreq CPU frequency scaling driver (i.e. the intel_pstate driver in passive mode), and all governors. It also happens with the acpi-cpufreq CPU frequency scaling driver, and all governors. However the manifestations of the incorrectly reported scaling_cur_freq can be anywhere from wrong to correct.
Example 1: 100% load on all 12 CPUs; acpi-cpufreq; schedutil: doug@s19:~$ grep . /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq:4800005 /sys/devices/system/cpu/cpu10/cpufreq/scaling_cur_freq:4101000 /sys/devices/system/cpu/cpu11/cpufreq/scaling_cur_freq:4101000 /sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq:4101000 /sys/devices/system/cpu/cpu2/cpufreq/scaling_cur_freq:4101000 /sys/devices/system/cpu/cpu3/cpufreq/scaling_cur_freq:4101000 /sys/devices/system/cpu/cpu4/cpufreq/scaling_cur_freq:4101000 /sys/devices/system/cpu/cpu5/cpufreq/scaling_cur_freq:4101000 /sys/devices/system/cpu/cpu6/cpufreq/scaling_cur_freq:4101000 /sys/devices/system/cpu/cpu7/cpufreq/scaling_cur_freq:4101000 /sys/devices/system/cpu/cpu8/cpufreq/scaling_cur_freq:4101000 /sys/devices/system/cpu/cpu9/cpufreq/scaling_cur_freq:4101000 except for CPU 0, which seems to be reporting as is it is using a different driver, the results are correct. Example 2: 100% load on CPU 4 only; acpi-cpufreq; ondemand: doug@s19:~$ grep . /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq:4799876 /sys/devices/system/cpu/cpu10/cpufreq/scaling_cur_freq:800000 /sys/devices/system/cpu/cpu11/cpufreq/scaling_cur_freq:800000 /sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq:800000 /sys/devices/system/cpu/cpu2/cpufreq/scaling_cur_freq:800000 /sys/devices/system/cpu/cpu3/cpufreq/scaling_cur_freq:800000 /sys/devices/system/cpu/cpu4/cpufreq/scaling_cur_freq:4101000 /sys/devices/system/cpu/cpu5/cpufreq/scaling_cur_freq:800000 /sys/devices/system/cpu/cpu6/cpufreq/scaling_cur_freq:800000 /sys/devices/system/cpu/cpu7/cpufreq/scaling_cur_freq:800000 /sys/devices/system/cpu/cpu8/cpufreq/scaling_cur_freq:800000 /sys/devices/system/cpu/cpu9/cpufreq/scaling_cur_freq:800000 Again, except for CPU 0, the results are correct. -- 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
