add docs

1 files changed, 7 insertions, 0 deletions

diff --git a/internal/flamegraph/counter.go b/internal/flamegraph/counter.go
index c12453a..ae727d4 100644
--- a/internal/flamegraph/counter.go
+++ b/internal/flamegraph/counter.go
@@ -4,6 +4,13 @@ import (
 	"fmt"
 )
 
+// Counter aggregates statistics for a logical flamegraph node.
+//
+// Duration and DurationToPrev use the same timing semantics as event.Pair:
+//   - Duration is the syscall runtime on the same thread.
+//   - DurationToPrev is the inter-syscall gap on the same thread and is attributed
+//     to the current node; there is no separate "idle" pseudo-node.
+// Bytes is only populated for read/write/transfer syscalls.
 type Counter struct {
 	Count          uint64
 	Duration       uint64