From: Rafael J. Wysocki <[email protected]> Make the schedutil governor compute the initial (default) value of the rate_limit_us sysfs attribute by multiplying the transition latency by a multiplier depending on the policy and set by the scaling driver (instead of using a constant for this purpose).
That will allow scaling drivers to make schedutil use smaller default values of rate_limit_us and reduce the default average time interval between consecutive frequency changes. Make intel_pstate use the opportunity to reduce the rate limit somewhat. Signed-off-by: Rafael J. Wysocki <[email protected]> --- drivers/cpufreq/cpufreq.c | 1 + drivers/cpufreq/intel_pstate.c | 2 ++ include/linux/cpufreq.h | 8 ++++++++ kernel/sched/cpufreq_schedutil.c | 2 +- 4 files changed, 12 insertions(+), 1 deletion(-) Index: linux-pm/drivers/cpufreq/cpufreq.c =================================================================== --- linux-pm.orig/drivers/cpufreq/cpufreq.c +++ linux-pm/drivers/cpufreq/cpufreq.c @@ -1072,6 +1072,7 @@ static struct cpufreq_policy *cpufreq_po init_waitqueue_head(&policy->transition_wait); init_completion(&policy->kobj_unregister); INIT_WORK(&policy->update, handle_update); + policy->latency_multiplier = LATENCY_MULTIPLIER; policy->cpu = cpu; return policy; Index: linux-pm/include/linux/cpufreq.h =================================================================== --- linux-pm.orig/include/linux/cpufreq.h +++ linux-pm/include/linux/cpufreq.h @@ -120,6 +120,14 @@ struct cpufreq_policy { bool fast_switch_possible; bool fast_switch_enabled; + /* + * Multiplier to apply to the transition latency to obtain the preferred + * average time interval between consecutive invocations of the driver + * to set the frequency for this policy. Initialized by the core to the + * LATENCY_MULTIPLIER value. + */ + unsigned int latency_multiplier; + /* Cached frequency lookup from cpufreq_driver_resolve_freq. */ unsigned int cached_target_freq; int cached_resolved_idx; Index: linux-pm/kernel/sched/cpufreq_schedutil.c =================================================================== --- linux-pm.orig/kernel/sched/cpufreq_schedutil.c +++ linux-pm/kernel/sched/cpufreq_schedutil.c @@ -530,7 +530,7 @@ static int sugov_init(struct cpufreq_pol goto stop_kthread; } - tunables->rate_limit_us = LATENCY_MULTIPLIER; + tunables->rate_limit_us = policy->latency_multiplier; lat = policy->cpuinfo.transition_latency / NSEC_PER_USEC; if (lat) tunables->rate_limit_us *= lat; Index: linux-pm/drivers/cpufreq/intel_pstate.c =================================================================== --- linux-pm.orig/drivers/cpufreq/intel_pstate.c +++ linux-pm/drivers/cpufreq/intel_pstate.c @@ -41,6 +41,7 @@ #define INTEL_PSTATE_HWP_SAMPLING_INTERVAL (50 * NSEC_PER_MSEC) #define INTEL_CPUFREQ_TRANSITION_LATENCY 20000 +#define INTEL_CPUFREQ_LATENCY_MULTIPLIER 250 #ifdef CONFIG_ACPI #include <acpi/processor.h> @@ -2237,6 +2238,7 @@ static int intel_cpufreq_cpu_init(struct return ret; policy->cpuinfo.transition_latency = INTEL_CPUFREQ_TRANSITION_LATENCY; + policy->latency_multiplier = INTEL_CPUFREQ_LATENCY_MULTIPLIER; /* This reflects the intel_pstate_get_cpu_pstates() setting. */ policy->cur = policy->cpuinfo.min_freq;
