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
