json: improve performance by using a pool of scanners (#535)

* add benchmark for each detector with it's corresponding file * json/ndjson: use a pool of scanners for detection it helps by reducing memory allocations to amortized 0 ➜ mimetype git:(bench) ✗ benchstat master sync_pool goos: linux goarch: amd64 pkg: github.com/gabriel-vasile/mimetype cpu: Intel(R) Core(TM) i7-10510U CPU @ 1.80GHz │ master │ sync_pool │ │ sec/op │ sec/op vs base │ Files/json.json/application/json-8 1.403µ ± 0% 1.355µ ± 1% -3.39% (p=0.000 n=20) Files/ndjson.xl.ndjson/application/x-ndjson-8 8.655µ ± 1% 8.504µ ± 1% -1.76% (p=0.001 n=20) Files/ndjson.ndjson/application/x-ndjson-8 3.069µ ± 1% 2.958µ ± 5% ~ (p=0.129 n=20) geomean 3.340µ 3.242µ -2.92% │ master │ sync_pool │ │ B/op │ B/op vs base │ Files/json.json/application/json-8 120.0 ± 0% 0.0 ± 0% -100.00% (p=0.000 n=20) Files/ndjson.xl.ndjson/application/x-ndjson-8 720.0 ± 0% 0.0 ± 0% -100.00% (p=0.000 n=20) Files/ndjson.ndjson/application/x-ndjson-8 240.0 ± 0% 0.0 ± 0% -100.00% (p=0.000 n=20) geomean 274.7 ? ¹ ² ¹ summaries must be >0 to compute geomean ² ratios must be >0 to compute geomean │ master │ sync_pool │ │ allocs/op │ allocs/op vs base │ Files/json.json/application/json-8 4.000 ± 0% 0.000 ± 0% -100.00% (p=0.000 n=20) Files/ndjson.xl.ndjson/application/x-ndjson-8 24.00 ± 0% 0.00 ± 0% -100.00% (p=0.000 n=20) Files/ndjson.ndjson/application/x-ndjson-8 8.000 ± 0% 0.000 ± 0% -100.00% (p=0.000 n=20) geomean 9.158 ? ¹ ² ¹ summaries must be >0 to compute geomean ² ratios must be >0 to compute geomean * benchmark: use sequential instead of concurrent benchmarks there is no reason to make it concurrent
gabriel-vasile · May 26, 2024 · 09ff708 · 09ff708
1 parent 43192c8
commit 09ff708
Show file tree

Hide file tree

Showing 2 changed files with 52 additions and 7 deletions.
diff --git a/internal/json/json.go b/internal/json/json.go
@@ -34,6 +34,7 @@ package json
 
 import (
 	"fmt"
+	"sync"
 )
 
 type (
@@ -73,18 +74,38 @@ type (
 	}
 )
 
+var scannerPool = sync.Pool{
+	New: func() any {
+		return &scanner{}
+	},
+}
+
+func newScanner() *scanner {
+	s := scannerPool.Get().(*scanner)
+	s.reset()
+	return s
+}
+
+func freeScanner(s *scanner) {
+	// Avoid hanging on to too much memory in extreme cases.
+	if len(s.parseState) > 1024 {
+		s.parseState = nil
+	}
+	scannerPool.Put(s)
+}
+
 // Scan returns the number of bytes scanned and if there was any error
 // in trying to reach the end of data.
 func Scan(data []byte) (int, error) {
-	s := &scanner{}
+	s := newScanner()
+	defer freeScanner(s)
 	_ = checkValid(data, s)
 	return s.index, s.err
 }
 
 // checkValid verifies that data is valid JSON-encoded data.
 // scan is passed in for use by checkValid to avoid an allocation.
 func checkValid(data []byte, scan *scanner) error {
-	scan.reset()
 	for _, c := range data {
 		scan.index++
 		if scan.step(scan, c) == scanError {
@@ -105,6 +126,8 @@ func (s *scanner) reset() {
 	s.step = stateBeginValue
 	s.parseState = s.parseState[0:0]
 	s.err = nil
+	s.endTop = false
+	s.index = 0
 }
 
 // eof tells the scanner that the end of input has been reached.

diff --git a/mimetype_test.go b/mimetype_test.go
@@ -488,11 +488,9 @@ func BenchmarkSliceRand(b *testing.B) {
 	b.ResetTimer()
 	b.ReportAllocs()
 
-	b.RunParallel(func(pb *testing.PB) {
-		for pb.Next() {
-			Detect(data)
-		}
-	})
+	for n := 0; n < b.N; n++ {
+		Detect(data)
+	}
 }
 
 func BenchmarkText(b *testing.B) {
@@ -513,6 +511,30 @@ func BenchmarkText(b *testing.B) {
 	}
 }
 
+// BenchmarkFiles benchmarks each detector with his coresponding file.
+func BenchmarkFiles(b *testing.B) {
+	for f, m := range files {
+		data, err := os.ReadFile(filepath.Join(testDataDir, f))
+		if err != nil {
+			b.Fatal(err)
+		}
+		if uint32(len(data)) > defaultLimit {
+			data = data[:defaultLimit]
+		}
+		b.Run(f+"/"+m, func(b *testing.B) {
+			b.ReportAllocs()
+			b.ResetTimer()
+			parsed, _, _ := mime.ParseMediaType(m)
+			mType := Lookup(parsed)
+			for n := 0; n < b.N; n++ {
+				if !mType.detector(data, uint32(len(data))) {
+					b.Fatal("detection should never fail")
+				}
+			}
+		})
+	}
+}
+
 func BenchmarkAll(b *testing.B) {
 	r := rand.New(rand.NewSource(0))
 	data := make([]byte, defaultLimit)