Add buffer pooling for JSON operations

Implement sync.Pool-based buffer pooling to reduce GC pressure
and memory allocations for JSON indentation operations.

Signed-off-by: Sascha Grunert <[email protected]>

Author: saschagrunert

cmd/crictl/bufferpool.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"bytes"
+	"sync"
+)
+
+// jsonBufferPool is a pool of bytes.Buffer instances used for JSON operations.
+// This reduces GC pressure by reusing buffers instead of allocating new ones
+// for each JSON indentation operation.
+var jsonBufferPool = sync.Pool{
+	New: func() interface{} {
+		return new(bytes.Buffer)
+	},
+}
+
+// getJSONBuffer retrieves a buffer from the pool.
+// The caller must call putJSONBuffer when done to return it to the pool.
+func getJSONBuffer() *bytes.Buffer {
+	buf, ok := jsonBufferPool.Get().(*bytes.Buffer)
+	if !ok {
+		return new(bytes.Buffer)
+	}
+
+	return buf
+}
+
+// putJSONBuffer resets and returns a buffer to the pool.
+// This should be called with defer after getJSONBuffer.
+func putJSONBuffer(buf *bytes.Buffer) {
+	buf.Reset()
+	jsonBufferPool.Put(buf)
+}

cmd/crictl/util.go

@@ -17,7 +17,6 @@ limitations under the License.
 package main
 
 import (
-	"bytes"
 	"context"
 	"encoding/json"
 	"errors"
@@ -421,8 +420,10 @@ func outputStatusData(statuses []statusData, format, tmplStr string) (err error)
 
 		fmt.Println(string(yamlInfo))
 	case outputTypeJSON:
-		var output bytes.Buffer
-		if err := json.Indent(&output, jsonResult, "", "  "); err != nil {
+		output := getJSONBuffer()
+		defer putJSONBuffer(output)
+
+		if err := json.Indent(output, jsonResult, "", "  "); err != nil {
 			return fmt.Errorf("indent JSON result: %w", err)
 		}
 
@@ -519,9 +520,10 @@ func marshalMapInOrder(m map[string]any, t any) (string, error) {
 
 	sb.WriteString("}")
 
-	var buf bytes.Buffer
+	buf := getJSONBuffer()
+	defer putJSONBuffer(buf)
 
-	if err := json.Indent(&buf, []byte(sb.String()), "", "  "); err != nil {
+	if err := json.Indent(buf, []byte(sb.String()), "", "  "); err != nil {
 		return "", err
 	}