Reduce allocations while creating a slice of keys from map and fix a …

…typo

fgprof.go

@@ -69,7 +69,7 @@ func (p *profiler) GoroutineProfile() []runtime.StackRecord {
 	// We don't know how many goroutines exist, so we have to grow p.stacks
 	// dynamically. We overshoot by 10% since it's possible that more goroutines
 	// are launched in between two calls to GoroutineProfile. Once p.stacks
-	// reaches the maximum numnber of goroutines used by the program, it will get
+	// reaches the maximum number of goroutines used by the program, it will get
 	// reused indefinitely, eliminating GoroutineProfile calls and allocations.
 	//
 	// TODO(fg) There might be workloads where it would be nice to shrink

format.go

@@ -9,6 +9,7 @@ import (
 	"github.com/google/pprof/profile"
 )
 
+// Format decides how the ouput is rendered to the user.
 type Format string
 
 const (
@@ -93,9 +94,11 @@ func toPprof(s map[string]int, hz int) *profile.Profile {
 }
 
 func sortedKeys(s map[string]int) []string {
-	var keys []string
+	keys := make([]string, len(s))
+	i := 0
 	for stack := range s {
-		keys = append(keys, stack)
+		keys[i] = stack
+		i++
 	}
 	sort.Strings(keys)
 	return keys