From c38ada1a2665033f9a2a4d8365ddb256c0dc0e1a Mon Sep 17 00:00:00 2001
From: Krishna Srinivas <634494+krishnasrinivas@users.noreply.github.com>
Date: Fri, 23 Aug 2019 15:36:46 -0700
Subject: [PATCH] write() to disk in 4MB blocks for better performance (#7888)

---
 cmd/posix.go         |  4 +--
 pkg/ioutil/ioutil.go | 74 +++++++++++++++++++++-----------------------
 2 files changed, 38 insertions(+), 40 deletions(-)

diff --git a/cmd/posix.go b/cmd/posix.go
index 027384666..dc04d9080 100644
--- a/cmd/posix.go
+++ b/cmd/posix.go
@@ -47,7 +47,7 @@ const (
 	diskMinFreeSpace  = 900 * humanize.MiByte // Min 900MiB free space.
 	diskMinTotalSpace = diskMinFreeSpace      // Min 900MiB total space.
 	maxAllowedIOError = 5
-	readBlockSize     = humanize.KiByte * 32 // Default read block size 32KiB.
+	readBlockSize     = 4 * humanize.MiByte // Default read block size 4MiB.
 )
 
 // isValidVolname verifies a volname name in accordance with object
@@ -1230,7 +1230,7 @@ func (s *posix) CreateFile(volume, path string, fileSize int64, r io.Reader) (er
 	bufp := s.pool.Get().(*[]byte)
 	defer s.pool.Put(bufp)
 
-	written, err := xioutil.CopyAligned(w, r, *bufp)
+	written, err := xioutil.CopyAligned(w, r, *bufp, fileSize)
 	if err != nil {
 		return err
 	}
diff --git a/pkg/ioutil/ioutil.go b/pkg/ioutil/ioutil.go
index 9094698d3..16cc4e132 100644
--- a/pkg/ioutil/ioutil.go
+++ b/pkg/ioutil/ioutil.go
@@ -173,7 +173,7 @@ const directioAlignSize = 4096
 // used with DIRECT I/O based file descriptor and it is expected that
 // input writer *os.File not a generic io.Writer. Make sure to have
 // the file opened for writes with syscall.O_DIRECT flag.
-func CopyAligned(w *os.File, r io.Reader, alignedBuf []byte) (int64, error) {
+func CopyAligned(w *os.File, r io.Reader, alignedBuf []byte, totalSize int64) (int64, error) {
 	// Writes remaining bytes in the buffer.
 	writeUnaligned := func(w *os.File, buf []byte) (remainingWritten int, err error) {
 		var n int
@@ -205,47 +205,45 @@ func CopyAligned(w *os.File, r io.Reader, alignedBuf []byte) (int64, error) {
 	}
 
 	var written int64
-	var err error
 	for {
-		nr, er := r.Read(alignedBuf)
-		if nr == len(alignedBuf) {
-			// Buffer read is aligned with input buffer, proceed to write.
-			nw, ew := w.Write(alignedBuf)
-			if nw > 0 {
-				written += int64(nw)
-			}
-			if ew != nil {
-				err = ew
-				break
-			}
-			if nr != nw {
-				err = io.ErrShortWrite
-				break
-			}
-		} else if nr > 0 {
-			// Buffer read is not aligned with input buffer, proceed to write
-			// whatever possible as aligned and turn off direct I/O.
-			nw, ew := writeUnaligned(w, alignedBuf[:nr])
-			if nw > 0 {
-				written += int64(nw)
-			}
-			if ew != nil {
-				err = ew
-				break
-			}
-			if nr != nw {
-				err = io.ErrShortWrite
-				break
+		buf := alignedBuf
+		if totalSize != -1 {
+			remaining := totalSize - written
+			if remaining < int64(len(buf)) {
+				buf = buf[:remaining]
 			}
 		}
-		// For any read errors break out and return error.
-		if er != nil {
-			if er != io.EOF {
-				err = er
+		nr, err := io.ReadFull(r, buf)
+		eof := err == io.EOF || err == io.ErrUnexpectedEOF
+		if err != nil && !eof {
+			return written, err
+		}
+		buf = buf[:nr]
+		var nw int
+		if len(buf)%directioAlignSize == 0 {
+			// buf is aligned for directio write()
+			nw, err = w.Write(buf)
+		} else {
+			// buf is not aligned, hence use writeUnaligned()
+			nw, err = writeUnaligned(w, buf)
+		}
+		if nw > 0 {
+			written += int64(nw)
+		}
+		if err != nil {
+			return written, err
+		}
+		if nw != len(buf) {
+			return written, io.ErrShortWrite
+		}
+
+		if totalSize != -1 {
+			if written == totalSize {
+				return written, nil
 			}
-			break
+		}
+		if eof {
+			return written, nil
 		}
 	}
-
-	return written, err
 }