archive, cio, cmd, linux: use buffer pools

To avoid buffer bloat in long running processes, we try to use buffer
pools where possible. This is meant to address shim memory usage issues,
but may not be the root cause.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

linux/bundle.go

@@ -3,9 +3,8 @@
 package linux
 
 import (
-	"bytes"
 	"context"
-	"io"
+	"io/ioutil"
 	"os"
 	"path/filepath"
 
@@ -52,12 +51,7 @@ func newBundle(id, path, workDir string, spec []byte) (b *bundle, err error) {
 	if err := os.Mkdir(filepath.Join(path, "rootfs"), 0711); err != nil {
 		return nil, err
 	}
-	f, err := os.Create(filepath.Join(path, configFilename))
-	if err != nil {
-		return nil, err
-	}
-	defer f.Close()
-	_, err = io.Copy(f, bytes.NewReader(spec))
+	err = ioutil.WriteFile(filepath.Join(path, configFilename), spec, 0666)
 	return &bundle{
 		id:      id,
 		path:    path,

linux/proc/io.go

@@ -13,6 +13,13 @@ import (
 	runc "github.com/containerd/go-runc"
 )
 
+var bufPool = sync.Pool{
+	New: func() interface{} {
+		buffer := make([]byte, 32<<10)
+		return &buffer
+	},
+}
+
 func copyPipes(ctx context.Context, rio runc.IO, stdin, stdout, stderr string, wg, cwg *sync.WaitGroup) error {
 	for name, dest := range map[string]func(wc io.WriteCloser, rc io.Closer){
 		stdout: func(wc io.WriteCloser, rc io.Closer) {
@@ -20,7 +27,9 @@ func copyPipes(ctx context.Context, rio runc.IO, stdin, stdout, stderr string, w
 			cwg.Add(1)
 			go func() {
 				cwg.Done()
-				io.Copy(wc, rio.Stdout())
+				p := bufPool.Get().(*[]byte)
+				defer bufPool.Put(p)
+				io.CopyBuffer(wc, rio.Stdout(), *p)
 				wg.Done()
 				wc.Close()
 				rc.Close()
@@ -31,7 +40,10 @@ func copyPipes(ctx context.Context, rio runc.IO, stdin, stdout, stderr string, w
 			cwg.Add(1)
 			go func() {
 				cwg.Done()
-				io.Copy(wc, rio.Stderr())
+				p := bufPool.Get().(*[]byte)
+				defer bufPool.Put(p)
+
+				io.CopyBuffer(wc, rio.Stderr(), *p)
 				wg.Done()
 				wc.Close()
 				rc.Close()
@@ -59,7 +71,10 @@ func copyPipes(ctx context.Context, rio runc.IO, stdin, stdout, stderr string, w
 	cwg.Add(1)
 	go func() {
 		cwg.Done()
-		io.Copy(rio.Stdin(), f)
+		p := bufPool.Get().(*[]byte)
+		defer bufPool.Put(p)
+
+		io.CopyBuffer(rio.Stdin(), f, *p)
 		rio.Stdin().Close()
 		f.Close()
 	}()

linux/proc/utils.go

@@ -66,7 +66,10 @@ func copyFile(to, from string) error {
 		return err
 	}
 	defer tt.Close()
-	_, err = io.Copy(tt, ff)
+
+	p := bufPool.Get().(*[]byte)
+	defer bufPool.Put(p)
+	_, err = io.CopyBuffer(tt, ff, *p)
 	return err
 }
 

linux/shim/service.go

@@ -29,7 +29,15 @@ import (
 	"google.golang.org/grpc/status"
 )
 
-var empty = &ptypes.Empty{}
+var (
+	empty   = &ptypes.Empty{}
+	bufPool = sync.Pool{
+		New: func() interface{} {
+			buffer := make([]byte, 32<<10)
+			return &buffer
+		},
+	}
+)
 
 // Config contains shim specific configuration
 type Config struct {

linux/shim/service_linux.go

@@ -33,7 +33,9 @@ func (p *linuxPlatform) CopyConsole(ctx context.Context, console console.Console
 		cwg.Add(1)
 		go func() {
 			cwg.Done()
-			io.Copy(epollConsole, in)
+			p := bufPool.Get().(*[]byte)
+			defer bufPool.Put(p)
+			io.CopyBuffer(epollConsole, in, *p)
 		}()
 	}
 
@@ -49,7 +51,9 @@ func (p *linuxPlatform) CopyConsole(ctx context.Context, console console.Console
 	cwg.Add(1)
 	go func() {
 		cwg.Done()
-		io.Copy(outw, epollConsole)
+		p := bufPool.Get().(*[]byte)
+		defer bufPool.Put(p)
+		io.CopyBuffer(outw, epollConsole, *p)
 		epollConsole.Close()
 		outr.Close()
 		outw.Close()

linux/shim/service_unix.go

@@ -24,7 +24,10 @@ func (p *unixPlatform) CopyConsole(ctx context.Context, console console.Console,
 		cwg.Add(1)
 		go func() {
 			cwg.Done()
-			io.Copy(console, in)
+			p := bufPool.Get().(*[]byte)
+			defer bufPool.Put(p)
+
+			io.CopyBuffer(console, in, *p)
 		}()
 	}
 	outw, err := fifo.OpenFifo(ctx, stdout, syscall.O_WRONLY, 0)
@@ -39,7 +42,10 @@ func (p *unixPlatform) CopyConsole(ctx context.Context, console console.Console,
 	cwg.Add(1)
 	go func() {
 		cwg.Done()
-		io.Copy(outw, console)
+		p := bufPool.Get().(*[]byte)
+		defer bufPool.Put(p)
+
+		io.CopyBuffer(outw, console, *p)
 		console.Close()
 		outr.Close()
 		outw.Close()