feat: add cpu_usage_pct metric (#28)

Author: vladkens

readme.md

@@ -114,6 +114,7 @@ This will collect 10 samples with an update interval of 500 milliseconds.
   },
   "ecpu_usage": [1181, 0.082656614],  // (Frequency MHz, Usage %)
   "pcpu_usage": [1974, 0.015181795],  // (Frequency MHz, Usage %)
+  "cpu_usage_pct": 0.036854,          // Combined CPU usage (weighted by core count, 0–1)
   "gpu_usage": [461, 0.021497859],    // (Frequency MHz, Usage %)
   "cpu_power": 0.20486385,            // Watts
   "gpu_power": 0.017451683,           // Watts
@@ -185,6 +186,10 @@ macmon_cpu_temp_celsius{chip="Apple M3 Pro"} 47.3
 # TYPE macmon_cpu_power_watts gauge
 macmon_cpu_power_watts{chip="Apple M3 Pro"} 8.42
 
+# HELP macmon_cpu_usage_ratio Combined CPU utilization (0–1), weighted by core count
+# TYPE macmon_cpu_usage_ratio gauge
+macmon_cpu_usage_ratio{chip="Apple M3 Pro"} 0.037
+
 # HELP macmon_ecpu_usage_ratio Efficiency CPU cluster utilization (0–1)
 # TYPE macmon_ecpu_usage_ratio gauge
 macmon_ecpu_usage_ratio{chip="Apple M3 Pro"} 0.083

src/metrics.rs

@@ -33,6 +33,7 @@ pub struct Metrics {
   pub memory: MemMetrics,
   pub ecpu_usage: (u32, f32), // freq, percent_from_max
   pub pcpu_usage: (u32, f32), // freq, percent_from_max
+  pub cpu_usage_pct: f32,     // combined ecpu+pcpu usage, weighted by core count
   pub gpu_usage: (u32, f32),  // freq, percent_from_max
   pub cpu_power: f32,         // Watts
   pub gpu_power: f32,         // Watts
@@ -279,11 +280,16 @@ impl Sampler {
       results.push(rs);
     }
 
+    let ecores = self.soc.ecpu_cores as f32;
+    let pcores = self.soc.pcpu_cores as f32;
+    let tcores = ecores + pcores;
+
     let mut rs = Metrics::default();
     rs.ecpu_usage.0 = zero_div(results.iter().map(|x| x.ecpu_usage.0).sum(), measures as _);
     rs.ecpu_usage.1 = zero_div(results.iter().map(|x| x.ecpu_usage.1).sum(), measures as _);
     rs.pcpu_usage.0 = zero_div(results.iter().map(|x| x.pcpu_usage.0).sum(), measures as _);
     rs.pcpu_usage.1 = zero_div(results.iter().map(|x| x.pcpu_usage.1).sum(), measures as _);
+    rs.cpu_usage_pct = zero_div(rs.ecpu_usage.1 * ecores + rs.pcpu_usage.1 * pcores, tcores);
     rs.gpu_usage.0 = zero_div(results.iter().map(|x| x.gpu_usage.0).sum(), measures as _);
     rs.gpu_usage.1 = zero_div(results.iter().map(|x| x.gpu_usage.1).sum(), measures as _);
     rs.cpu_power = zero_div(results.iter().map(|x| x.cpu_power).sum(), measures as _);

src/serve.rs

@@ -28,6 +28,7 @@ fn to_prometheus(m: &Metrics, soc: &SocInfo) -> String {
   gauge!(out, "macmon_memory_ram_used_bytes", "Used RAM in bytes", m.memory.ram_usage);
   gauge!(out, "macmon_memory_swap_total_bytes", "Total swap in bytes", m.memory.swap_total);
   gauge!(out, "macmon_memory_swap_used_bytes", "Used swap in bytes", m.memory.swap_usage);
+  gauge!(out, "macmon_cpu_usage_ratio", "Combined CPU utilization (0–1), weighted by core count", m.cpu_usage_pct);
   gauge!(out, "macmon_ecpu_freq_mhz", "Efficiency CPU cluster frequency in MHz", m.ecpu_usage.0);
   gauge!(out, "macmon_ecpu_usage_ratio", "Efficiency CPU cluster utilization (0–1)", m.ecpu_usage.1);
   gauge!(out, "macmon_pcpu_freq_mhz", "Performance CPU cluster frequency in MHz", m.pcpu_usage.0);