1 files changed, 145 insertions, 0 deletions
diff --git a/pkg/state/stats.go b/pkg/state/stats.go
new file mode 100644
index 000000000..eaec664a1
--- /dev/null
+++ b/pkg/state/stats.go
@@ -0,0 +1,145 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package state
+
+import (
+	"bytes"
+	"fmt"
+	"sort"
+	"time"
+)
+
+type statEntry struct {
+	count uint
+	total time.Duration
+}
+
+// Stats tracks encode / decode timing.
+//
+// This currently provides a meaningful String function and no other way to
+// extract stats about individual types.
+//
+// All exported receivers accept nil.
+type Stats struct {
+	// byType contains a breakdown of time spent by type.
+	//
+	// This is indexed *directly* by typeID, including zero.
+	byType []statEntry
+
+	// stack contains objects in progress.
+	stack []typeID
+
+	// names contains type names.
+	//
+	// This is also indexed *directly* by typeID, including zero, which we
+	// hard-code as "state.default". This is only resolved by calling fini
+	// on the stats object.
+	names []string
+
+	// last is the last start time.
+	last time.Time
+}
+
+// init initializes statistics.
+func (s *Stats) init() {
+	s.last = time.Now()
+	s.stack = append(s.stack, 0)
+}
+
+// fini finalizes statistics.
+func (s *Stats) fini(resolve func(id typeID) string) {
+	s.done()
+
+	// Resolve all type names.
+	s.names = make([]string, len(s.byType))
+	s.names[0] = "state.default" // See above.
+	for id := typeID(1); int(id) < len(s.names); id++ {
+		s.names[id] = resolve(id)
+	}
+}
+
+// sample adds the samples to the given object.
+func (s *Stats) sample(id typeID) {
+	now := time.Now()
+	if len(s.byType) <= int(id) {
+		// Allocate all the missing entries in one fell swoop.
+		s.byType = append(s.byType, make([]statEntry, 1+int(id)-len(s.byType))...)
+	}
+	s.byType[id].total += now.Sub(s.last)
+	s.last = now
+}
+
+// start starts a sample.
+func (s *Stats) start(id typeID) {
+	last := s.stack[len(s.stack)-1]
+	s.sample(last)
+	s.stack = append(s.stack, id)
+}
+
+// done finishes the current sample.
+func (s *Stats) done() {
+	last := s.stack[len(s.stack)-1]
+	s.sample(last)
+	s.byType[last].count++
+	s.stack = s.stack[:len(s.stack)-1]
+}
+
+type sliceEntry struct {
+	name  string
+	entry *statEntry
+}
+
+// String returns a table representation of the stats.
+func (s *Stats) String() string {
+	// Build a list of stat entries.
+	ss := make([]sliceEntry, 0, len(s.byType))
+	for id := 0; id < len(s.names); id++ {
+		ss = append(ss, sliceEntry{
+			name:  s.names[id],
+			entry: &s.byType[id],
+		})
+	}
+
+	// Sort by total time (descending).
+	sort.Slice(ss, func(i, j int) bool {
+		return ss[i].entry.total > ss[j].entry.total
+	})
+
+	// Print the stat results.
+	var (
+		buf   bytes.Buffer
+		count uint
+		total time.Duration
+	)
+	buf.WriteString("\n")
+	buf.WriteString(fmt.Sprintf("% 16s | % 8s | % 16s | %s\n", "total", "count", "per", "type"))
+	buf.WriteString("-----------------+----------+------------------+----------------\n")
+	for _, se := range ss {
+		if se.entry.count == 0 {
+			// Since we store all types linearly, we are not
+			// guaranteed that any entry actually has time.
+			continue
+		}
+		count += se.entry.count
+		total += se.entry.total
+		per := se.entry.total / time.Duration(se.entry.count)
+		buf.WriteString(fmt.Sprintf("% 16s | %8d | % 16s | %s\n",
+			se.entry.total, se.entry.count, per, se.name))
+	}
+	buf.WriteString("-----------------+----------+------------------+----------------\n")
+	buf.WriteString(fmt.Sprintf("% 16s | % 8d | % 16s | [all]",
+		total, count, total/time.Duration(count)))
+	return string(buf.Bytes())
+}