threshold default value is now relative to the CPU number

obsdfreqd uses hw.ncpuonline to calculate a threshold
matching 80% of a single core usage. This helps the
default value to work fine with computer from 1 to many cores.

README.md

@@ -52,7 +52,7 @@ Parameters are applied when both plugged on the wall or on battery, parameters c
 - `-i inertia` sets the number of cycles after which the frequency will decay, 0 is the default
 - `-m maxfrequency` sets the maximum frequency the CPU can reach in percent, 100% is default
 - `-l minfrequency` sets the minimum frequency the CPU must be lowered to, 0% is default
-- `-r threshold` sets the CPU usage in % that will trigger the frequency increase, 30% is the default
+- `-r threshold` sets the CPU usage in % that will trigger the frequency increase, defaults to 80% of a single core.
 - `-s stepfrequency` sets the percent of frequency added every cycle when increasing, 10% is default
 - `-t timefreq` sets the milliseconds between each poll, 300 is the default
 - `-T maxtemperature` sets the temperature threshold under which the maximum frequency will be temporary lowered until the CPU cools down

main.c

@@ -52,6 +52,7 @@ int temperature_sensor_found;
 
 void try_to_find_default_temperature_sensor(void);
 int  get_temp(void);
+int  get_cpu_online(void);
 void set_policy(const char*);
 void quit_gracefully(int signum);
 void usage(void);
@@ -159,6 +160,21 @@ int get_temp() {
     return(value);
 }
 
+/* get the number of online CPUs */
+int get_cpu_online(void) {
+    int mib_cpu[2] =	{ CTL_HW,	HW_NCPUONLINE };
+    int ncpu = 1;
+    size_t len_ncpu = sizeof(len_ncpu);
+
+    if (sysctl(mib_cpu, 2, &ncpu, &len_ncpu, NULL, 0) == -1)
+        err(1, "sysctl");
+
+    if (ncpu <= 0)
+        err(1, "cpuonline detection");
+
+    return(ncpu);
+}
+
 /* define the policy to auto or manual */
 void set_policy(const char* policy) {
     int mib[2] = { CTL_HW, HW_PERFPOLICY };
@@ -425,11 +441,17 @@ int main(int argc, char *argv[]) {
     int cpu_usage_percent = 0, cpu_usage;
     float temp;
     size_t len, len_cpu;
+    int ncpu;
+
+    ncpu = get_cpu_online();
 
     // battery defaults
     hard_min_freq =	batt_min=	0;
     hard_max_freq =	batt_max=	100;
-    threshold =		batt_threshold=	30;
+
+    // threshold defaults to 80% usage of one CPU
+    threshold =		batt_threshold=	floor(100/ncpu*0.8);
+
     down_step =		batt_down_step=	100;
     inertia =		batt_inertia=	5;
     step =		batt_step=	100;

obsdfreqd.1

@@ -44,6 +44,8 @@ Defines the maximum frequency in percent the CPU can be increased to.
 Defines the minimum frequency in percent the CPU can be reduced to.
 .It Fl r Ar threshold
 Defines the CPU usage in percent above which the frequency is increased.
+The default is to use a value that match the usage of 80% of a single core.
+Example: for a 4 CPU system, the threshold will be 100/4*0.8 = 20%
 .It Fl s Ar stepfrequency
 Defines the frequency increase step in percent.
 .It Fl t Ar timefrequency