archiver: Improve buffer pool

internal/archiver/archiver.go

@@ -172,7 +172,7 @@ func (arch *Archiver) saveTree(ctx context.Context, t *restic.Tree) (restic.ID,
 	// adds a newline after each object)
 	buf = append(buf, '\n')
 
-	b := Buffer{Data: buf}
+	b := &Buffer{Data: buf}
 	res := arch.blobSaver.Save(ctx, restic.TreeBlob, b)
 	if res.Err() != nil {
 		return restic.ID{}, s, res.Err()

internal/archiver/blob_saver.go

@@ -45,7 +45,7 @@ func NewBlobSaver(ctx context.Context, repo Saver, workers uint) *BlobSaver {
 // Save stores a blob in the repo. It checks the index and the known blobs
 // before saving anything. The second return parameter is true if the blob was
 // previously unknown.
-func (s *BlobSaver) Save(ctx context.Context, t restic.BlobType, buf Buffer) FutureBlob {
+func (s *BlobSaver) Save(ctx context.Context, t restic.BlobType, buf *Buffer) FutureBlob {
 	ch := make(chan saveBlobResponse, 1)
 	s.ch <- saveBlobJob{BlobType: t, buf: buf, ch: ch}
 
@@ -91,7 +91,7 @@ func (s *FutureBlob) Length() int {
 
 type saveBlobJob struct {
 	restic.BlobType
-	buf Buffer
+	buf *Buffer
 	ch  chan<- saveBlobResponse
 }
 

internal/archiver/buffer.go

@@ -9,19 +9,19 @@ import (
 // be called so the underlying slice is put back into the pool.
 type Buffer struct {
 	Data []byte
-	Put  func([]byte)
+	Put  func(*Buffer)
 }
 
 // Release puts the buffer back into the pool it came from.
-func (b Buffer) Release() {
+func (b *Buffer) Release() {
 	if b.Put != nil {
-		b.Put(b.Data)
+		b.Put(b)
 	}
 }
 
 // BufferPool implements a limited set of reusable buffers.
 type BufferPool struct {
-	ch          chan []byte
+	ch          chan *Buffer
 	chM         sync.Mutex
 	defaultSize int
 	clearOnce   sync.Once
@@ -33,7 +33,7 @@ type BufferPool struct {
 // back.
 func NewBufferPool(ctx context.Context, max int, defaultSize int) *BufferPool {
 	b := &BufferPool{
-		ch:          make(chan []byte, max),
+		ch:          make(chan *Buffer, max),
 		defaultSize: defaultSize,
 	}
 	go func() {
@@ -44,22 +44,29 @@ func NewBufferPool(ctx context.Context, max int, defaultSize int) *BufferPool {
 }
 
 // Get returns a new buffer, either from the pool or newly allocated.
-func (pool *BufferPool) Get() Buffer {
-	b := Buffer{Put: pool.put}
-
+func (pool *BufferPool) Get() *Buffer {
 	pool.chM.Lock()
 	defer pool.chM.Unlock()
 	select {
 	case buf := <-pool.ch:
-		b.Data = buf
+		return buf
 	default:
-		b.Data = make([]byte, pool.defaultSize)
+	}
+
+	b := &Buffer{
+		Put:  pool.Put,
+		Data: make([]byte, pool.defaultSize),
 	}
 
 	return b
 }
 
-func (pool *BufferPool) put(b []byte) {
+// Put returns a buffer to the pool for reuse.
+func (pool *BufferPool) Put(b *Buffer) {
+	if cap(b.Data) > pool.defaultSize {
+		return
+	}
+
 	pool.chM.Lock()
 	defer pool.chM.Unlock()
 	select {
@@ -68,14 +75,6 @@ func (pool *BufferPool) put(b []byte) {
 	}
 }
 
-// Put returns a buffer to the pool for reuse.
-func (pool *BufferPool) Put(b Buffer) {
-	if cap(b.Data) > pool.defaultSize {
-		return
-	}
-	pool.put(b.Data)
-}
-
 // clear empties the buffer so that all items can be garbage collected.
 func (pool *BufferPool) clear() {
 	pool.clearOnce.Do(func() {

internal/archiver/file_saver.go

@@ -61,20 +61,19 @@ type FileSaver struct {
 	NodeFromFileInfo func(filename string, fi os.FileInfo) (*restic.Node, error)
 }
 
-// NewFileSaver returns a new file saver. A worker pool with workers is
+// NewFileSaver returns a new file saver. A worker pool with fileWorkers is
 // started, it is stopped when ctx is cancelled.
 func NewFileSaver(ctx context.Context, fs fs.FS, blobSaver *BlobSaver, pol chunker.Pol, fileWorkers, blobWorkers uint) *FileSaver {
-	ch := make(chan saveFileJob, fileWorkers)
+	ch := make(chan saveFileJob)
 
-	poolSize := fileWorkers
-	if blobWorkers > fileWorkers {
-		poolSize = blobWorkers
-	}
+	debug.Log("new file saver with %v file workers and %v blob workers", fileWorkers, blobWorkers)
+
+	poolSize := fileWorkers + blobWorkers
 
 	s := &FileSaver{
 		fs:           fs,
 		blobSaver:    blobSaver,
-		saveFilePool: NewBufferPool(ctx, int(poolSize)*3/2, chunker.MaxSize/2),
+		saveFilePool: NewBufferPool(ctx, int(poolSize), chunker.MaxSize),
 		pol:          pol,
 		ch:           ch,
 
@@ -156,6 +155,7 @@ func (s *FileSaver) saveFile(ctx context.Context, chnker *chunker.Chunker, snPat
 			buf.Release()
 			break
 		}
+
 		buf.Data = chunk.Data
 
 		size += uint64(chunk.Length)