From: Rafael J. Wysocki Date: Wed, 18 Jul 2018 08:15:07 +0000 (+0200) Subject: cpufreq: pcc-cpufreq: Disable dynamic scaling on many-CPU systems X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=4d81b0f9e631f751bf231213893e202a51f76687;p=linux.git cpufreq: pcc-cpufreq: Disable dynamic scaling on many-CPU systems 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 Tested-by: Andreas Herrmann Signed-off-by: Rafael J. Wysocki --- diff --git a/drivers/cpufreq/pcc-cpufreq.c b/drivers/cpufreq/pcc-cpufreq.c index 3f0ce2ae35ee4..ef8d984178a5e 100644 --- a/drivers/cpufreq/pcc-cpufreq.c +++ b/drivers/cpufreq/pcc-cpufreq.c @@ -589,6 +589,15 @@ static int __init pcc_cpufreq_init(void) return ret; } + if (num_present_cpus() > 4) { + pcc_cpufreq_driver.flags |= CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING; + pr_err("%s: Too many CPUs, dynamic performance scaling disabled\n", + __func__); + pr_err("%s: Try to enable another scaling driver through BIOS settings\n", + __func__); + pr_err("%s: and complain to the system vendor\n", __func__); + } + ret = cpufreq_register_driver(&pcc_cpufreq_driver); return ret;