Messages in this thread Patch in this message | | | From | Prarit Bhargava <> | Subject | [PATCH] cpufreq, intel_pstate, set max_sysfs_pct and min_sysfs_pct on governor switch | Date | Tue, 6 Oct 2015 17:49:07 -0400 |
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Intel CPUs will not enter higher p-states when after switching from the performance governor to the powersave governor, until /sys/devices/system/cpu/intel_pstate/min_perf_pct is set to a low value. This differs from previous behaviour in which a switch to the powersave governor would result in a low default value for min_perf_pct.
The behavior of the powersave governor changed after commit a04759924e25 ("[cpufreq] intel_pstate: honor user space min_perf_pct override on resume"). The commit introduced tracking of performance percentage changes via sysfs in order to restore userspace changes during suspend/resume. The problem occurs because the global values of the newly introduced max_sysfs_pct and min_sysfs_pct are not reset on a governor change and this causes the new governor to inherit the previous governor's settings.
This patch sets max_sysfs_pct to 100 and min_sysfs_pct to 0 on a governor change which fixes the problem with governor switching. These changes also make the initial calculations for max_perf_pct and min_perf_pct slightly simpler.
Before patch: [root@intel-skylake-y-01 power]# cpupower frequency-set -g performance [root@intel-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/min_perf_pct 100 [root@intel-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/max_perf_pct 100 [root@intel-skylake-y-01 power]# cpupower frequency-set -g powersave [root@intel-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/min_perf_pct 100 [root@intel-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/max_perf_pct 100
After patch: [root@intel-skylake-y-01 power]# cpupower frequency-set -g performance [root@intel-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/min_perf_pct 100 [root@intel-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/max_perf_pct 100 [root@intel-skylake-y-01 power]# cpupower frequency-set -g powersave [root@intel-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/min_perf_pct 14 [root@intel-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/max_perf_pct 100
Also note that I have tested suspend/resume (using CONFIG_PM_DEBUG): [root@intel-skylake-y-01 power]# echo 50 > /sys/devices/system/cpu/intel_pstate/min_perf_pct [root@intel-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/*_perf_pct 100 50 [root@intel-skylake-y-01 power]# echo devices > /sys/power/pm_test [root@intel-skylake-y-01 power]# echo platform > /sys/power/disk [root@intel-skylake-y-01 power]# echo disk > /sys/power/state [root@intel-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/*_perf_pct 100 50
Fixes: a04759924e25 ("[cpufreq] intel_pstate: honor user space min_perf_pct override on resume") Cc: Kristen Carlson Accardi <kristen@linux.intel.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: linux-pm@vger.kernel.org Signed-off-by: Prarit Bhargava <prarit@redhat.com> --- drivers/cpufreq/intel_pstate.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 3af9dd7..bb24458 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -986,6 +986,9 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy) if (!policy->cpuinfo.max_freq) return -ENODEV; + limits.min_sysfs_pct = 0; + limits.max_sysfs_pct = 100; + if (policy->policy == CPUFREQ_POLICY_PERFORMANCE && policy->max >= policy->cpuinfo.max_freq) { limits.min_policy_pct = 100; @@ -1004,9 +1007,9 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy) limits.max_policy_pct = clamp_t(int, limits.max_policy_pct, 0 , 100); /* Normalize user input to [min_policy_pct, max_policy_pct] */ - limits.min_perf_pct = max(limits.min_policy_pct, limits.min_sysfs_pct); + limits.min_perf_pct = limits.min_policy_pct; limits.min_perf_pct = min(limits.max_policy_pct, limits.min_perf_pct); - limits.max_perf_pct = min(limits.max_policy_pct, limits.max_sysfs_pct); + limits.max_perf_pct = limits.max_sysfs_pct; limits.max_perf_pct = max(limits.min_policy_pct, limits.max_perf_pct); /* Make sure min_perf_pct <= max_perf_pct */ -- 1.7.9.3
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