re-use io.Copy buffers with 32k pools (#13553)

Borrowed idea from Go's usage of this
optimization for ReadFrom() on client
side, we should re-use the 32k buffers
io.Copy() allocates for generic copy
from a reader to writer.

the performance increase for reads for
really tiny objects is at this range
after this change.

> * Fastest: +7.89% (+1.3 MiB/s) throughput, +7.89% (+1308.1) obj/s

cmd/erasure-utils.go

@@ -24,6 +24,7 @@ import (
 	"io"
 
 	"github.com/klauspost/reedsolomon"
+	xioutil "github.com/minio/minio/internal/ioutil"
 	"github.com/minio/minio/internal/logger"
 )
 
@@ -82,7 +83,7 @@ func writeDataBlocks(ctx context.Context, dst io.Writer, enBlocks [][]byte, data
 
 		// We have written all the blocks, write the last remaining block.
 		if write < int64(len(block)) {
-			n, err := io.Copy(dst, bytes.NewReader(block[:write]))
+			n, err := xioutil.Copy(dst, bytes.NewReader(block[:write]))
 			if err != nil {
 				// The writer will be closed incase of range queries, which will emit ErrClosedPipe.
 				// The reader pipe might be closed at ListObjects io.EOF ignore it.
@@ -96,7 +97,7 @@ func writeDataBlocks(ctx context.Context, dst io.Writer, enBlocks [][]byte, data
 		}
 
 		// Copy the block.
-		n, err := io.Copy(dst, bytes.NewReader(block))
+		n, err := xioutil.Copy(dst, bytes.NewReader(block))
 		if err != nil {
 			// The writer will be closed incase of range queries, which will emit ErrClosedPipe.
 			// The reader pipe might be closed at ListObjects io.EOF ignore it.

cmd/fs-v1-helpers.go

@@ -26,6 +26,7 @@ import (
 	"strings"
 	"time"
 
+	xioutil "github.com/minio/minio/internal/ioutil"
 	"github.com/minio/minio/internal/lock"
 	"github.com/minio/minio/internal/logger"
 )
@@ -334,7 +335,7 @@ func fsCreateFile(ctx context.Context, filePath string, reader io.Reader, falloc
 	}
 	defer writer.Close()
 
-	bytesWritten, err := io.Copy(writer, reader)
+	bytesWritten, err := xioutil.Copy(writer, reader)
 	if err != nil {
 		logger.LogIf(ctx, err)
 		return 0, err

cmd/object-api-interface.go

@@ -26,8 +26,10 @@ import (
 	"github.com/minio/madmin-go"
 	"github.com/minio/minio-go/v7/pkg/encrypt"
 	"github.com/minio/minio-go/v7/pkg/tags"
-	"github.com/minio/minio/internal/bucket/replication"
 	"github.com/minio/pkg/bucket/policy"
+
+	"github.com/minio/minio/internal/bucket/replication"
+	xioutil "github.com/minio/minio/internal/ioutil"
 )
 
 // CheckPreconditionFn returns true if precondition check failed.
@@ -261,6 +263,6 @@ func GetObject(ctx context.Context, api ObjectLayer, bucket, object string, star
 	}
 	defer reader.Close()
 
-	_, err = io.Copy(writer, reader)
+	_, err = xioutil.Copy(writer, reader)
 	return err
 }

cmd/object-handlers.go

@@ -54,7 +54,7 @@ import (
 	"github.com/minio/minio/internal/handlers"
 	"github.com/minio/minio/internal/hash"
 	xhttp "github.com/minio/minio/internal/http"
-	"github.com/minio/minio/internal/ioutil"
+	xioutil "github.com/minio/minio/internal/ioutil"
 	"github.com/minio/minio/internal/kms"
 	"github.com/minio/minio/internal/logger"
 	"github.com/minio/minio/internal/s3select"
@@ -504,14 +504,14 @@ func (api objectAPIHandlers) getObjectHandler(ctx context.Context, objectAPI Obj
 	setHeadGetRespHeaders(w, r.Form)
 
 	statusCodeWritten := false
-	httpWriter := ioutil.WriteOnClose(w)
+	httpWriter := xioutil.WriteOnClose(w)
 	if rs != nil || opts.PartNumber > 0 {
 		statusCodeWritten = true
 		w.WriteHeader(http.StatusPartialContent)
 	}
 
 	// Write object content to response body
-	if _, err = io.Copy(httpWriter, gr); err != nil {
+	if _, err = xioutil.Copy(httpWriter, gr); err != nil {
 		if !httpWriter.HasWritten() && !statusCodeWritten {
 			// write error response only if no data or headers has been written to client yet
 			writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)

cmd/s3-zip-handlers.go

@@ -23,13 +23,13 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	stdioutil "io/ioutil"
+	"io/ioutil"
 	"net/http"
 	"sort"
 	"strings"
 
 	"github.com/minio/minio/internal/crypto"
-	"github.com/minio/minio/internal/ioutil"
+	xioutil "github.com/minio/minio/internal/ioutil"
 	"github.com/minio/minio/internal/logger"
 	"github.com/minio/pkg/bucket/policy"
 	xnet "github.com/minio/pkg/net"
@@ -187,7 +187,7 @@ func (api objectAPIHandlers) getObjectInArchiveFileHandler(ctx context.Context,
 			return
 		}
 	} else {
-		rc = stdioutil.NopCloser(bytes.NewReader([]byte{}))
+		rc = ioutil.NopCloser(bytes.NewReader([]byte{}))
 	}
 
 	defer rc.Close()
@@ -199,10 +199,10 @@ func (api objectAPIHandlers) getObjectInArchiveFileHandler(ctx context.Context,
 
 	setHeadGetRespHeaders(w, r.Form)
 
-	httpWriter := ioutil.WriteOnClose(w)
+	httpWriter := xioutil.WriteOnClose(w)
 
 	// Write object content to response body
-	if _, err = io.Copy(httpWriter, rc); err != nil {
+	if _, err = xioutil.Copy(httpWriter, rc); err != nil {
 		if !httpWriter.HasWritten() {
 			// write error response only if no data or headers has been written to client yet
 			writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
@@ -324,7 +324,7 @@ func getFilesListFromZIPObject(ctx context.Context, objectAPI ObjectLayer, bucke
 		if err != nil {
 			return nil, ObjectInfo{}, err
 		}
-		b, err := stdioutil.ReadAll(gr)
+		b, err := ioutil.ReadAll(gr)
 		if err != nil {
 			gr.Close()
 			return nil, ObjectInfo{}, err

cmd/storage-rest-server.go

@@ -41,6 +41,7 @@ import (
 	"github.com/gorilla/mux"
 	"github.com/minio/minio/internal/config"
 	xhttp "github.com/minio/minio/internal/http"
+	xioutil "github.com/minio/minio/internal/ioutil"
 	xjwt "github.com/minio/minio/internal/jwt"
 	"github.com/minio/minio/internal/logger"
 	xnet "github.com/minio/pkg/net"
@@ -574,7 +575,7 @@ func (s *storageRESTServer) ReadFileStreamHandler(w http.ResponseWriter, r *http
 	defer rc.Close()
 
 	w.Header().Set(xhttp.ContentLength, strconv.Itoa(length))
-	if _, err = io.Copy(w, rc); err != nil {
+	if _, err = xioutil.Copy(w, rc); err != nil {
 		if !xnet.IsNetworkOrHostDown(err, true) { // do not need to log disconnected clients
 			logger.LogIf(r.Context(), err)
 		}
@@ -954,13 +955,22 @@ func streamHTTPResponse(w http.ResponseWriter) *httpStreamResponse {
 	return &h
 }
 
+var poolBuf8k = sync.Pool{
+	New: func() interface{} {
+		b := make([]byte, 8192)
+		return &b
+	},
+}
+
 // waitForHTTPStream will wait for responses where
 // streamHTTPResponse has been used.
 // The returned reader contains the payload and must be closed if no error is returned.
 func waitForHTTPStream(respBody io.ReadCloser, w io.Writer) error {
 	var tmp [1]byte
 	// 8K copy buffer, reused for less allocs...
-	var buf [8 << 10]byte
+	bufp := poolBuf8k.Get().(*[]byte)
+	buf := *bufp
+	defer poolBuf8k.Put(bufp)
 	for {
 		_, err := io.ReadFull(respBody, tmp[:])
 		if err != nil {
@@ -970,7 +980,7 @@ func waitForHTTPStream(respBody io.ReadCloser, w io.Writer) error {
 		switch tmp[0] {
 		case 0:
 			// 0 is unbuffered, copy the rest.
-			_, err := io.CopyBuffer(w, respBody, buf[:])
+			_, err := io.CopyBuffer(w, respBody, buf)
 			if err == io.EOF {
 				return nil
 			}
@@ -989,7 +999,7 @@ func waitForHTTPStream(respBody io.ReadCloser, w io.Writer) error {
 				return err
 			}
 			length := binary.LittleEndian.Uint32(tmp[:])
-			_, err = io.CopyBuffer(w, io.LimitReader(respBody, int64(length)), buf[:])
+			_, err = io.CopyBuffer(w, io.LimitReader(respBody, int64(length)), buf)
 			if err != nil {
 				return err
 			}

cmd/warm-backend-gcs.go

@@ -27,6 +27,8 @@ import (
 	"google.golang.org/api/googleapi"
 	"google.golang.org/api/iterator"
 	"google.golang.org/api/option"
+
+	xioutil "github.com/minio/minio/internal/ioutil"
 )
 
 type warmBackendGCS struct {
@@ -54,7 +56,7 @@ func (gcs *warmBackendGCS) Put(ctx context.Context, key string, data io.Reader,
 	if gcs.StorageClass != "" {
 		w.ObjectAttrs.StorageClass = gcs.StorageClass
 	}
-	if _, err := io.Copy(w, data); err != nil {
+	if _, err := xioutil.Copy(w, data); err != nil {
 		return "", gcsToObjectError(err, gcs.Bucket, key)
 	}
 

internal/ioutil/ioutil.go

@@ -24,6 +24,7 @@ import (
 	"context"
 	"io"
 	"os"
+	"sync"
 	"time"
 
 	"github.com/minio/minio/internal/disk"
@@ -210,6 +211,22 @@ func NewSkipReader(r io.Reader, n int64) io.Reader {
 	return &SkipReader{r, n}
 }
 
+var copyBufPool = sync.Pool{
+	New: func() interface{} {
+		b := make([]byte, 32*1024)
+		return &b
+	},
+}
+
+// Copy is exactly like io.Copy but with re-usable buffers.
+func Copy(dst io.Writer, src io.Reader) (written int64, err error) {
+	bufp := copyBufPool.Get().(*[]byte)
+	buf := *bufp
+	defer copyBufPool.Put(bufp)
+
+	return io.CopyBuffer(dst, src, buf)
+}
+
 // SameFile returns if the files are same.
 func SameFile(fi1, fi2 os.FileInfo) bool {
 	if !os.SameFile(fi1, fi2) {
@@ -250,6 +267,7 @@ func CopyAligned(w *os.File, r io.Reader, alignedBuf []byte, totalSize int64) (i
 		if err = disk.DisableDirectIO(w); err != nil {
 			return remainingWritten, err
 		}
+		// Since w is *os.File io.Copy shall use ReadFrom() call.
 		return io.Copy(w, bytes.NewReader(buf))
 	}