daemon: lower allocations

Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com>

daemon/exec.go

@@ -11,6 +11,7 @@ import (
 	"github.com/docker/docker/daemon/execdriver"
 	"github.com/docker/docker/pkg/broadcastwriter"
 	"github.com/docker/docker/pkg/ioutils"
+	"github.com/docker/docker/pkg/pools"
 	"github.com/docker/docker/pkg/stringid"
 	"github.com/docker/docker/runconfig"
 )
@@ -183,7 +184,7 @@ func (d *Daemon) ContainerExecStart(execName string, stdin io.ReadCloser, stdout
 		go func() {
 			defer w.Close()
 			defer logrus.Debugf("Closing buffered stdin pipe")
-			io.Copy(w, stdin)
+			pools.Copy(w, stdin)
 		}()
 		cStdin = r
 	}

daemon/execdriver/native/driver.go

@@ -16,6 +16,7 @@ import (
 	"github.com/Sirupsen/logrus"
 	"github.com/docker/docker/daemon/execdriver"
 	"github.com/docker/docker/pkg/parsers"
+	"github.com/docker/docker/pkg/pools"
 	"github.com/docker/docker/pkg/reexec"
 	sysinfo "github.com/docker/docker/pkg/system"
 	"github.com/docker/docker/pkg/term"
@@ -394,12 +395,12 @@ func (t *TtyConsole) AttachPipes(pipes *execdriver.Pipes) error {
 			defer wb.CloseWriters()
 		}
 
-		io.Copy(pipes.Stdout, t.console)
+		pools.Copy(pipes.Stdout, t.console)
 	}()
 
 	if pipes.Stdin != nil {
 		go func() {
-			io.Copy(t.console, pipes.Stdin)
+			pools.Copy(t.console, pipes.Stdin)
 
 			pipes.Stdin.Close()
 		}()

pkg/pools/pools.go

@@ -57,6 +57,14 @@ func (bufPool *BufioReaderPool) Put(b *bufio.Reader) {
 	bufPool.pool.Put(b)
 }
 
+// Copy is a convenience wrapper which uses a buffer to avoid allocation in io.Copy
+func Copy(dst io.Writer, src io.Reader) (written int64, err error) {
+	buf := BufioReader32KPool.Get(src)
+	written, err = io.Copy(dst, buf)
+	BufioReader32KPool.Put(buf)
+	return
+}
+
 // NewReadCloserWrapper returns a wrapper which puts the bufio.Reader back
 // into the pool and closes the reader if it's an io.ReadCloser.
 func (bufPool *BufioReaderPool) NewReadCloserWrapper(buf *bufio.Reader, r io.Reader) io.ReadCloser {