Use Sync.Pool pointers to optimise memory usage

Signed-off-by: Paulo Gomes <pjbgf@linux.com>

plumbing/format/objfile/writer.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"io"
 	"strconv"
+	"sync"
 
 	"github.com/go-git/go-git/v5/plumbing"
 )
@@ -18,9 +19,9 @@ var (
 // not close the underlying io.Writer.
 type Writer struct {
 	raw    io.Writer
-	zlib   io.WriteCloser
 	hasher plumbing.Hasher
 	multi  io.Writer
+	zlib   io.WriteCloser
 
 	closed  bool
 	pending int64 // number of unwritten bytes
@@ -31,12 +32,21 @@ type Writer struct {
 // The returned Writer implements io.WriteCloser. Close should be called when
 // finished with the Writer. Close will not close the underlying io.Writer.
 func NewWriter(w io.Writer) *Writer {
+	zlib := zlibPool.Get().(*zlib.Writer)
+	zlib.Reset(w)
+
 	return &Writer{
 		raw:  w,
-		zlib: zlib.NewWriter(w),
+		zlib: zlib,
 	}
 }
 
+var zlibPool = sync.Pool{
+	New: func() interface{} {
+		return zlib.NewWriter(nil)
+	},
+}
+
 // WriteHeader writes the type and the size and prepares to accept the object's
 // contents. If an invalid t is provided, plumbing.ErrInvalidType is returned. If a
 // negative size is provided, ErrNegativeSize is returned.
@@ -100,6 +110,7 @@ func (w *Writer) Hash() plumbing.Hash {
 // Calling Close does not close the wrapped io.Writer originally passed to
 // NewWriter.
 func (w *Writer) Close() error {
+	defer zlibPool.Put(w.zlib)
 	if err := w.zlib.Close(); err != nil {
 		return err
 	}

plumbing/format/packfile/parser_test.go

@@ -10,8 +10,10 @@ import (
 	fixtures "github.com/go-git/go-git-fixtures/v4"
 	"github.com/go-git/go-git/v5"
 	"github.com/go-git/go-git/v5/plumbing"
+	"github.com/go-git/go-git/v5/plumbing/cache"
 	"github.com/go-git/go-git/v5/plumbing/format/packfile"
 	"github.com/go-git/go-git/v5/plumbing/storer"
+	"github.com/go-git/go-git/v5/storage/filesystem"
 	. "gopkg.in/check.v1"
 )
 
@@ -248,3 +250,29 @@ func BenchmarkParseBasic(b *testing.B) {
 		}
 	}
 }
+
+func BenchmarkParser(b *testing.B) {
+	f := fixtures.Basic().One()
+	defer fixtures.Clean()
+
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		b.StopTimer()
+		scanner := packfile.NewScanner(f.Packfile())
+		fs := osfs.New(os.TempDir())
+		storage := filesystem.NewStorage(fs, cache.NewObjectLRUDefault())
+
+		parser, err := packfile.NewParserWithStorage(scanner, storage)
+		if err != nil {
+			b.Error(err)
+		}
+
+		b.StartTimer()
+		_, err = parser.Parse()
+
+		b.StopTimer()
+		if err != nil {
+			b.Error(err)
+		}
+	}
+}

plumbing/format/packfile/patch_delta.go

@@ -53,9 +53,10 @@ func ApplyDelta(target, base plumbing.EncodedObject, delta []byte) (err error) {
 
 	target.SetSize(int64(dst.Len()))
 
-	b := byteSlicePool.Get().([]byte)
+	bufp := byteSlicePool.Get().(*[]byte)
+	b := *bufp
 	_, err = io.CopyBuffer(w, dst, b)
-	byteSlicePool.Put(b)
+	byteSlicePool.Put(bufp)
 	return err
 }
 

plumbing/format/packfile/scanner.go

@@ -346,15 +346,17 @@ func (s *Scanner) copyObject(w io.Writer) (n int64, err error) {
 	}
 
 	defer ioutil.CheckClose(zr, &err)
-	buf := byteSlicePool.Get().([]byte)
+	bufp := byteSlicePool.Get().(*[]byte)
+	buf := *bufp
 	n, err = io.CopyBuffer(w, zr, buf)
-	byteSlicePool.Put(buf)
+	byteSlicePool.Put(bufp)
 	return
 }
 
 var byteSlicePool = sync.Pool{
 	New: func() interface{} {
-		return make([]byte, 32*1024)
+		b := make([]byte, 32*1024)
+		return &b
 	},
 }
 
@@ -387,9 +389,11 @@ func (s *Scanner) Checksum() (plumbing.Hash, error) {
 
 // Close reads the reader until io.EOF
 func (s *Scanner) Close() error {
-	buf := byteSlicePool.Get().([]byte)
+	bufp := byteSlicePool.Get().(*[]byte)
+	buf := *bufp
 	_, err := io.CopyBuffer(stdioutil.Discard, s.r, buf)
-	byteSlicePool.Put(buf)
+	byteSlicePool.Put(bufp)
+
 	return err
 }
 

storage/filesystem/object.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"io"
 	"os"
+	"sync"
 	"time"
 
 	"github.com/go-git/go-git/v5/plumbing"
@@ -419,10 +420,21 @@ func (s *ObjectStorage) getFromUnpacked(h plumbing.Hash) (obj plumbing.EncodedOb
 
 	s.objectCache.Put(obj)
 
-	_, err = io.Copy(w, r)
+	bufp := copyBufferPool.Get().(*[]byte)
+	buf := *bufp
+	_, err = io.CopyBuffer(w, r, buf)
+	copyBufferPool.Put(bufp)
+
 	return obj, err
 }
 
+var copyBufferPool = sync.Pool{
+	New: func() interface{} {
+		b := make([]byte, 32*1024)
+		return &b
+	},
+}
+
 // Get returns the object with the given hash, by searching for it in
 // the packfile.
 func (s *ObjectStorage) getFromPackfile(h plumbing.Hash, canBeDelta bool) (

worktree.go

@@ -534,7 +534,8 @@ func (w *Worktree) checkoutChangeRegularFile(name string,
 
 var copyBufferPool = sync.Pool{
 	New: func() interface{} {
-		return make([]byte, 32*1024)
+		b := make([]byte, 32*1024)
+		return &b
 	},
 }
 
@@ -561,9 +562,10 @@ func (w *Worktree) checkoutFile(f *object.File) (err error) {
 	}
 
 	defer ioutil.CheckClose(to, &err)
-	buf := copyBufferPool.Get().([]byte)
+	bufp := copyBufferPool.Get().(*[]byte)
+	buf := *bufp
 	_, err = io.CopyBuffer(to, from, buf)
-	copyBufferPool.Put(buf)
+	copyBufferPool.Put(bufp)
 	return
 }