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authorPhilippe Longepe <philippe.longepe@intel.com>2015-12-04 17:40:32 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2015-12-10 01:17:40 +0100
commite70eed2b64545ab5c9d2f4d43372d79762f1b985 (patch)
treedd00eb9d051a1ee5ba0bedd474cc1c085278ab31 /drivers/cpufreq
parent157386b6fc1465f292b66c4133409033650ad335 (diff)
downloadop-kernel-dev-e70eed2b64545ab5c9d2f4d43372d79762f1b985.zip
op-kernel-dev-e70eed2b64545ab5c9d2f4d43372d79762f1b985.tar.gz
cpufreq: intel_pstate: Account for non C0 time
The current function to calculate cpu utilization uses the average P-state ratio (APerf/Mperf) scaled by the ratio of the current P-state to the max available non-turbo one. This leads to an overestimation of utilization which causes higher-performance P-states to be selected more often and that leads to increased energy consumption. This is a problem for low-power systems, so it is better to use a different utilization calculation algorithm for them. Namely, the Percent Busy value (or load) can be estimated as the ratio of the MPERF counter that runs at a constant rate only during active periods (C0) to the time stamp counter (TSC) that also runs (at the same rate) during idle. That is: Percent Busy = 100 * (delta_mperf / delta_tsc) Use this algorithm for platforms with SoCs based on the Airmont and Silvermont Atom cores. Signed-off-by: Philippe Longepe <philippe.longepe@intel.com> Signed-off-by: Stephane Gasparini <stephane.gasparini@intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpufreq')
-rw-r--r--drivers/cpufreq/intel_pstate.c29
1 files changed, 24 insertions, 5 deletions
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index ff58029..8bfebae 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -143,6 +143,7 @@ struct cpu_defaults {
};
static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu);
+static inline int32_t get_target_pstate_use_cpu_load(struct cpudata *cpu);
static struct pstate_adjust_policy pid_params;
static struct pstate_funcs pstate_funcs;
@@ -763,7 +764,7 @@ static struct cpu_defaults silvermont_params = {
.set = atom_set_pstate,
.get_scaling = silvermont_get_scaling,
.get_vid = atom_get_vid,
- .get_target_pstate = get_target_pstate_use_performance,
+ .get_target_pstate = get_target_pstate_use_cpu_load,
},
};
@@ -784,7 +785,7 @@ static struct cpu_defaults airmont_params = {
.set = atom_set_pstate,
.get_scaling = airmont_get_scaling,
.get_vid = atom_get_vid,
- .get_target_pstate = get_target_pstate_use_performance,
+ .get_target_pstate = get_target_pstate_use_cpu_load,
},
};
@@ -890,12 +891,11 @@ static inline void intel_pstate_sample(struct cpudata *cpu)
local_irq_save(flags);
rdmsrl(MSR_IA32_APERF, aperf);
rdmsrl(MSR_IA32_MPERF, mperf);
- if (cpu->prev_mperf == mperf) {
+ tsc = rdtsc();
+ if ((cpu->prev_mperf == mperf) || (cpu->prev_tsc == tsc)) {
local_irq_restore(flags);
return;
}
-
- tsc = rdtsc();
local_irq_restore(flags);
cpu->last_sample_time = cpu->sample.time;
@@ -930,6 +930,25 @@ static inline void intel_pstate_set_sample_time(struct cpudata *cpu)
mod_timer_pinned(&cpu->timer, jiffies + delay);
}
+static inline int32_t get_target_pstate_use_cpu_load(struct cpudata *cpu)
+{
+ struct sample *sample = &cpu->sample;
+ int32_t cpu_load;
+
+ /*
+ * The load can be estimated as the ratio of the mperf counter
+ * running at a constant frequency during active periods
+ * (C0) and the time stamp counter running at the same frequency
+ * also during C-states.
+ */
+ cpu_load = div64_u64(int_tofp(100) * sample->mperf, sample->tsc);
+
+ cpu->sample.busy_scaled = cpu_load;
+
+ return cpu->pstate.current_pstate - pid_calc(&cpu->pid, cpu_load);
+}
+
+
static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu)
{
int32_t core_busy, max_pstate, current_pstate, sample_ratio;
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