fix: add gcGuard to prevent GC during Marshal()/Unmarshal() (#122)

Co-authored-by: duanyi.aster <duanyi.aster@bytedance.com>

decoder/decoder.go

@@ -19,6 +19,7 @@ package decoder
 import (
     `encoding/json`
     `reflect`
+    `runtime`
 
     `github.com/bytedance/sonic/internal/rt`
 )
@@ -70,6 +71,9 @@ func (self *Decoder) Decode(val interface{}) error {
     /* return the stack back */
     self.i = nb
     freeStack(sb)
+
+    /* avoid GC ahead */
+    runtime.KeepAlive(vv)
     return err
 }
 
@@ -105,4 +109,4 @@ func (self *Decoder) DisallowUnknownFields() {
 func Pretouch(vt reflect.Type) (err error) {
     _, err = findOrCompile(rt.UnpackType(vt))
     return
-}
+}

encoder/encoder.go

@@ -20,6 +20,7 @@ import (
     `bytes`
     `encoding/json`
     `reflect`
+    `runtime`
 
     `github.com/bytedance/sonic/internal/rt`
 )
@@ -102,6 +103,9 @@ func EncodeInto(buf *[]byte, val interface{}, opts Options) error {
 
     /* return the stack into pool */
     freeStack(stk)
+
+    /* avoid GC ahead */
+    runtime.KeepAlive(efv)
     return err
 }
 

issue_test/issue123_test.go

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2021 ByteDance Inc.
+ *
+ * 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 issue_test
+
+import (
+	`encoding/json`
+	`fmt`
+	`sync`
+	`testing`
+
+	`github.com/bytedance/sonic`
+)
+
+func TestGcWriteBarrier(t *testing.T) {
+	// debug.SetGCPercent(-1)
+	size := 10_0000
+	data := make([]int, size)
+	date, _ := json.Marshal(data)	
+
+	// debug.SetGCPercent(-1)
+	wg := sync.WaitGroup{}
+
+	for i := 0; i < 1000; i++ {
+		wg.Add(1)
+		cd := make([]byte, len(date))
+		copy(cd, date)
+		go func() {
+			var w []int
+			defer wg.Done()
+			// Decode
+			if err := sonic.Unmarshal(cd, &w); err != nil {
+				fmt.Println(err)
+			}
+		}()
+	}
+	wg.Wait()
+}
+
+func BenchmarkGcGuard(b *testing.B) {
+	size := 10_0000
+	data := make([]int, size)
+	date, _ := json.Marshal(data)
+	b.RunParallel(func(p *testing.PB) {
+		for p.Next() {
+			var w []int
+			_ = sonic.Unmarshal(date, &w)
+		}
+	})
+}