docs: clarify which raw performance counters need a multiplier (#2775)

Co-authored-by: Claude <noreply@anthropic.com>
Signed-off-by: Claude <noreply@anthropic.com>

internal/collector/performancecounter/performancecounter_test_test.go

@@ -442,8 +442,8 @@ func TestCollectorMetricTypePerCounter(t *testing.T) {
 }
 
 // TestCollectorMultiplier checks that the multiplier scales the exported value.
-// Commit Limit only changes when a page file is resized, so both objects read
-// the same value.
+// Commit Limit only changes when a page file grows or is resized, which is
+// unlikely between the two reads, so both objects read the same value.
 func TestCollectorMultiplier(t *testing.T) {
 	t.Parallel()
 

internal/multiplier/multiplier.go

@@ -23,8 +23,8 @@ import (
 	"math"
 )
 
-// maxExactInteger is the largest integer up to which every integer has an
-// exact float64 representation.
+// maxExactInteger bounds the divisor. Beyond it, several integers round to the
+// same reciprocal, so the rounded divisor may not be the one the user meant.
 const maxExactInteger = 1 << 53
 
 // Multiplier scales values. The zero value leaves them unchanged.

internal/multiplier/multiplier_test.go

@@ -61,8 +61,8 @@ func TestNewInvalid(t *testing.T) {
 }
 
 // TestApplyDividesExactly checks that a multiplier that is the reciprocal of
-// an integer gives the correctly rounded quotient, which a plain
-// multiplication misses for about one in seven values.
+// an integer gives the correctly rounded quotient. A plain multiplication
+// misses it for some values, for example 9 * 0.001.
 func TestApplyDividesExactly(t *testing.T) {
 	t.Parallel()