On Tue, Jul 17, 2018 at 10:13 PM, Andreas Herrmann <[email protected]> wrote: > On Tue, Jul 17, 2018 at 06:14:58PM +0200, Rafael J. Wysocki wrote: >> From: Rafael J. Wysocki <[email protected]> >> >> The firmware interface used by the pcc-cpufreq driver is >> fundamentally not scalable and using it for dynamic CPU performance >> scaling on systems with many CPUs leads to degraded performance. >> >> For this reason, disable dynamic CPU performance scaling on systems >> with pcc-cpufreq where the number of CPUs present at the driver init >> time is greater than 4. Also make the driver print corresponding >> complaints to the kernel log. >> >> Reported-by: Andreas Herrmann <[email protected]> >> Signed-off-by: Rafael J. Wysocki <[email protected]> >> --- >> >> -> v2: Rework the messages printed in the problematic case. > > I've tested this patch. Effect is as expected: driver loads but use of > ondemand governor is not allowed. Sample output: > > [ 40.757519] pcc-cpufreq: (v1.10.00) driver loaded with frequency limits: > 1200 MHz, 2800 MHz > [ 40.831705] pcc_cpufreq_init: Too many CPUs, dynamic performance scaling > disabled > [ 40.898353] pcc_cpufreq_init: Try to enable a different scaling driver > through BIOS settings > [ 40.972327] pcc_cpufreq_init: and complain to the system vendor > [ 41.025620] cpufreq: Can't use ondemand governor as dynamic switching is > disallowed. Fallback to performance governor > ... > [ 41.187928] cpufreq: Can't use ondemand governor as dynamic switching is > disallowed. Fallback to performance governor > > Last message is shown for each online CPU in the system (ie. 120x). > > Looks good to me.
Thanks a lot! Please also try https://patchwork.kernel.org/patch/10530321/ Cheers, Rafael
