From 3e822e5138238b6cb612942f6397bc513ace358d Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@sbcglobal.net>
Date: Sat, 18 Jun 2016 05:02:51 -0400
Subject: Use a pool of byte arrays to reduce GC pressure.

---
 proto/io.go                           | 57 +++++++++++++++++++++++++++++++++--
 proto/server/func_handlerequest.go.sh |  4 +++
 2 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/proto/io.go b/proto/io.go
index 34421b1..0f231c8 100644
--- a/proto/io.go
+++ b/proto/io.go
@@ -23,6 +23,7 @@ import (
 	"io"
 	"net"
 	"reflect"
+	"sync"
 	"syscall"
 )
 
@@ -41,6 +42,7 @@ type nslcdObjectPtr interface {
 }
 
 type String []byte
+
 func (s String) String() string {
 	return string(s)
 }
@@ -54,7 +56,7 @@ func (data String) nslcdWrite(fd io.Writer) {
 func (data *String) nslcdRead(fd io.Reader) {
 	var len int32
 	Read(fd, &len)
-	buf := make([]byte, len)
+	buf := makeBytes(len)
 	Read(fd, &buf)
 	*data = String(buf)
 }
@@ -94,7 +96,7 @@ func Write(fd io.Writer, data interface{}) {
 		}
 		var bytes []byte
 		if af < 0 {
-			bytes = make([]byte, 0)
+			bytes = makeBytes(0)
 		} else {
 			bytes = data
 		}
@@ -163,7 +165,7 @@ func Read(fd io.Reader, data interface{}) {
 		if len != _len {
 			panic(NslcdError(fmt.Sprintf("address length incorrect: %d", len)))
 		}
-		buf := make([]byte, len)
+		buf := makeBytes(len)
 		Read(fd, &buf)
 		*data = buf
 	case *[]net.IP:
@@ -184,3 +186,52 @@ func Read(fd io.Reader, data interface{}) {
 		}
 	}
 }
+
+// "Free" an object and its members, returning them to various pools.
+// This keeps the GC sane.
+func Free(data interface{}) {
+	switch data := data.(type) {
+	case *[]byte:
+		bytePool.Put(*data)
+	case *int32:
+		// do nothing
+	case *String:
+		bytes := []byte(*data)
+		bytePool.Put(bytes)
+	case *[]String:
+		for _, str := range *data {
+			Free(&str)
+		}
+	case *net.IP:
+		bytes := []byte(*data)
+		bytePool.Put(bytes)
+	case *[]net.IP:
+		for _, ip := range *data {
+			Free(&ip)
+		}
+	default:
+		p := reflect.ValueOf(data)
+		v := reflect.Indirect(p)
+		if p == v || v.Kind() != reflect.Struct {
+			panic(fmt.Sprintf("The argument to nslcd_proto.Free() must be a pointer: %T ( %#v )", data, data))
+		}
+		for i, n := 0, v.NumField(); i < n; i++ {
+			Free(v.Field(i).Addr().Interface())
+		}
+	}
+}
+
+var bytePool = sync.Pool{
+	New: func() interface{} {
+		return make([]byte, 0, 256)
+	},
+}
+
+func makeBytes(l int32) []byte {
+	buf := bytePool.Get().([]byte)
+	if cap(buf) < int(l) {
+		bytePool.Put(buf)
+		buf = make([]byte, l)
+	}
+	return buf[:l]
+}
diff --git a/proto/server/func_handlerequest.go.sh b/proto/server/func_handlerequest.go.sh
index 0dffe39..ea07439 100755
--- a/proto/server/func_handlerequest.go.sh
+++ b/proto/server/func_handlerequest.go.sh
@@ -75,6 +75,7 @@ while read -r request; do
 				echo '_req := req'
 				echo '_req.Password = sensitive'
 				echo 'fmt.Fprintf(os.Stderr, "Request: %#v\n", _req)'
+				echo 'p.Free(&_req)'
 				;;
 			PAM_PwMod)
 				echo '_req := req'
@@ -83,11 +84,13 @@ while read -r request; do
 				echo '}'
 				echo '_req.NewPassword = sensitive'
 				echo 'fmt.Fprintf(os.Stderr, "Request: %#v\n", _req)'
+				echo 'p.Free(&_req)'
 				;;
 			PAM_UserMod)
 				echo '_req := req'
 				echo '_req.Password = sensitive'
 				echo 'fmt.Fprintf(os.Stderr, "Request: %#v\n", _req)'
+				echo 'p.Free(&_req)'
 				;;
 			*)
 				echo 'fmt.Fprintf(os.Stderr, "Request: %#v\n", req)'
@@ -96,6 +99,7 @@ while read -r request; do
 		)
 		_ch := backend.${request}(cred, req)
 		go func() {
+			defer p.Free(&req)
 			defer close(ch)
 			for obj := range _ch {
 				ch <- obj
-- 
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