p2p: initialize maps with known size (#27229)

p2p/netutil/iptrack.go

@@ -78,7 +78,7 @@ func (it *IPTracker) PredictEndpoint() string {
 	it.gcStatements(it.clock.Now())
 
 	// The current strategy is simple: find the endpoint with most statements.
-	counts := make(map[string]int)
+	counts := make(map[string]int, len(it.statements))
 	maxcount, max := 0, ""
 	for _, s := range it.statements {
 		c := counts[s.endpoint] + 1