Restructure stats into delta, mask, and aggregate layers

tx.go

@@ -17,13 +17,12 @@ type txStats struct {
 }
 
 type txWorker struct {
-	fd        int
-	stream    uint16
-	spec      *frameSpec
-	batch     int
-	stats     *txStats
-	measuring *atomic.Bool
-	startTx   <-chan struct{}
+	fd      int
+	stream  uint16
+	spec    *frameSpec
+	batch   int
+	stats   *txStats
+	startTx <-chan struct{}
 }
 
 func (w *txWorker) run(done *atomic.Bool) {
@@ -64,8 +63,7 @@ func (w *txWorker) run(done *atomic.Bool) {
 		}
 		// Taking fewer of the vector than offered is the ring's room, not a frame
 		// lost: the rest go on the next pass.
-		if n < 0 && err != unix.EINTR && err != unix.EAGAIN && err != unix.ENOBUFS &&
-			!w.measuring.Load() {
+		if n < 0 && err != unix.EINTR && err != unix.EAGAIN && err != unix.ENOBUFS {
 			w.stats.errs.Add(1)
 		}
 	}