Am Dienstag, dem 12.07.2022 um 18:55 +0200 schrieb Thomas HUMMEL: > Hello, > > I'm using systemd-239-45 on RHEL 8.4 x86_64 AMD nodes on which I disable > Turbo Core/Turbo Boost by writing '0' into the following file: > > /sys/devices/system/cpu/cpufreq/boost > > I want it to be disabled automatically at boot. For that matter I tried > 3 different ways (only one at a time) > > 1) a service unit configured like this: > > [Unit] > Description=Disable CPU Turbo Boost > > > [Service] > # using tee here to have an output in journalctl to understand when this > service > # fails to start > ExecStart=/bin/sh -c "/usr/bin/echo 0 | /bin/tee > /sys/devices/system/cpu/cpufreq/boost" > ExecStop=/bin/sh -c "/usr/bin/echo 1 | /bin/tee > /sys/devices/system/cpu/cpufreq/boost" > RemainAfterExit=yes > > [Install] > WantedBy=sysinit.target > > 2) adding an entry for systemd-tmpfiles-setup.service like this: > > w /sys/devices/system/cpu/cpufreq/boost - - - - 0 > > 3) using modprobe.d like this: > > install acpi_cpufreq /sbin/modprobe --ignore-install acpi_cpufreq > $CMDLINE_OPTS && echo 0 > /sys/devices/system/cpu/cpufreq/boost > > > I noticed that *sometimes* using 1) or 2) > /sys/devices/system/cpu/cpufreq/boost ended up with '1' instead of '0' > > I didn't see any error in journal for 2) (tmpfiles.d option) and for 1) > (systemd service) I saw: > > > Jul 04 15:06:25 xxxx systemd[1]: Started Disable CPU Turbo Boost. > Jul 04 15:06:25 xxxx sh[2788]: /bin/tee: > /sys/devices/system/cpu/cpufreq/boost: Permission denied > Jul 04 15:06:25 xxxx sh[2788]: 0 > Jul 04 15:06:25 xxxx systemd[1]: disable-cpu-turboboost.service: Main > process exited, code=exited, status=1/FAILURE > Jul 04 15:06:25 xxxx systemd[1]: disable-cpu-turboboost.service: Failed > with result 'exit-code'. > > I did not manage to find out if there were a race condition and if so > what ordering dependencies should be stated. > I tried to compare a "working" and "not working" systemd-analyse output > but I did not find anything obvious (at least for me) > > Besides, /sys is mounted in the fstab (as expected) > > sysfs /sys sysfs defaults 0 0 > > is there a corresponding transient .mount unit somewhere ? > > Notes: > > a) SELinux is disabled > > b) I don't think any other service or process is touching the > /sys/devices/system/cpu/cpufreq/boost file > > c) in the event the system boot up with the wrong value, manually echo 0 > into the file (which exists) always work > > Can you help me figuring in what direction I should look, if it is > systemd related at all ? > > Thanks for your help > > -- > Thomas HUMMEL Hi, first of all, no need for /sys in /etc/fstab. /sys will _always_ be mounted by systemd. Second, this sounds really depending on your used driver (acpi, amd, or intel). Check out the documentation at https://docs.kernel.org/admin-guide/pm/cpufreq.html and always check the Arch wiki https://wiki.archlinux.org/title/CPU_frequency_scaling as well. Question I have is: why do you want to disable boosting? BR Silvio
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