Support hardware counters (instructions, cache misses, ...) (#983)

* Add hardware counters to JSON exports

* Clarify Linux hardware counter setup

src/quantity/mod.rs

@@ -34,6 +34,12 @@ impl<U: uom::si::information::Unit + uom::Conversion<f64, T = f64>> QuantityInUn
     }
 }
 
+impl<U: uom::si::ratio::Unit + uom::Conversion<f64, T = f64>> QuantityInUnit<U> for Ratio {
+    fn value_in_unit(self) -> f64 {
+        self.get::<U>()
+    }
+}
+
 pub trait FormatQuantity {
     type Unit;
 

src/quantity/statistics.rs

@@ -91,6 +91,16 @@ impl UnsafeRawValue for Information {
     }
 }
 
+impl UnsafeRawValue for Ratio {
+    fn unsafe_raw_value(&self) -> f64 {
+        self.get::<ratio>()
+    }
+
+    fn unsafe_from_raw_value(value: f64) -> Self {
+        Ratio::new::<ratio>(value)
+    }
+}
+
 fn standard_deviation_f64(values: &[f64]) -> f64 {
     let mean_value = mean(values.iter().copied());