add []byte caching and pooling

fixes https://github.com/chrislusf/seaweedfs/issues/211

go/storage/needle.go

@@ -13,7 +13,6 @@ import (
 	"github.com/chrislusf/seaweedfs/go/glog"
 	"github.com/chrislusf/seaweedfs/go/images"
 	"github.com/chrislusf/seaweedfs/go/operation"
-	"github.com/chrislusf/seaweedfs/go/util"
 )
 
 const (
@@ -23,14 +22,6 @@ const (
 	MaxPossibleVolumeSize = 4 * 1024 * 1024 * 1024 * 8
 )
 
-var (
-	BYTESPOOL *util.BytesPool
-)
-
-func init() {
-	BYTESPOOL = util.NewBytesPool()
-}
-
 /*
 * A Needle means a uploaded and stored file.
 * Needle file size is limited to 4GB for now.
@@ -53,7 +44,7 @@ type Needle struct {
 	Checksum CRC    `comment:"CRC32 to check integrity"`
 	Padding  []byte `comment:"Aligned to 8 bytes"`
 
-	rawBytes []byte // underlying supporing []byte, fetched and released into a pool
+	rawBlock *Block // underlying supporing []byte, fetched and released into a pool
 }
 
 func (n *Needle) String() (str string) {

go/storage/needle_byte_cache.go

@@ -0,0 +1,70 @@
+package storage
+
+import (
+	"fmt"
+	"os"
+	"sync/atomic"
+
+	"github.com/hashicorp/golang-lru"
+
+	"github.com/chrislusf/seaweedfs/go/util"
+)
+
+var (
+	bytesCache *lru.Cache
+	bytesPool  *util.BytesPool
+)
+
+/*
+There are one level of caching, and one level of pooling.
+
+In pooling, all []byte are fetched and returned to the pool bytesPool.
+
+In caching, the string~[]byte mapping is cached, to
+*/
+func init() {
+	bytesPool = util.NewBytesPool()
+	bytesCache, _ = lru.NewWithEvict(1, func(key interface{}, value interface{}) {
+		value.(*Block).decreaseReference()
+	})
+}
+
+type Block struct {
+	Bytes    []byte
+	refCount int32
+}
+
+func (block *Block) decreaseReference() {
+	if atomic.AddInt32(&block.refCount, -1) == 0 {
+		bytesPool.Put(block.Bytes)
+	}
+}
+func (block *Block) increaseReference() {
+	atomic.AddInt32(&block.refCount, 1)
+}
+
+// get bytes from the LRU cache of []byte first, then from the bytes pool
+// when []byte in LRU cache is evicted, it will be put back to the bytes pool
+func getBytesForFileBlock(r *os.File, offset int64, readSize int) (block *Block, isNew bool) {
+	// check cache, return if found
+	cacheKey := fmt.Sprintf("%d:%d:%d", r.Fd(), offset>>3, readSize)
+	if obj, found := bytesCache.Get(cacheKey); found {
+		block = obj.(*Block)
+		block.increaseReference()
+		return block, false
+	}
+
+	// get the []byte from pool
+	b := bytesPool.Get(readSize)
+	// refCount = 2, one by the bytesCache, one by the actual needle object
+	block = &Block{Bytes: b, refCount: 2}
+	bytesCache.Add(cacheKey, block)
+	return block, true
+}
+
+func (n *Needle) ReleaseMemory() {
+	n.rawBlock.decreaseReference()
+}
+func ReleaseBytes(b []byte) {
+	bytesPool.Put(b)
+}

go/storage/needle_read_write.go

@@ -136,33 +136,20 @@ func (n *Needle) Append(w io.Writer, version Version) (size uint32, err error) {
 	return 0, fmt.Errorf("Unsupported Version! (%d)", version)
 }
 
-func ReleaseBytes(b []byte) {
-	// println("Releasing", len(b))
-	BYTESPOOL.Put(b)
-}
-
-func BorrwoBytes(size int) []byte {
-	ret := BYTESPOOL.Get(size)
-	// println("Reading", len(ret))
-	return ret
-}
-
-func ReadNeedleBlob(r *os.File, offset int64, size uint32) (dataSlice, rawBytes []byte, err error) {
+func ReadNeedleBlob(r *os.File, offset int64, size uint32) (dataSlice []byte, block *Block, err error) {
 	padding := NeedlePaddingSize - ((NeedleHeaderSize + size + NeedleChecksumSize) % NeedlePaddingSize)
 	readSize := NeedleHeaderSize + size + NeedleChecksumSize + padding
-	rawBytes = BorrwoBytes(int(readSize))
-	dataSlice = rawBytes[0:int(readSize)]
-	_, err = r.ReadAt(dataSlice, offset)
-	return
-}
-
-func (n *Needle) ReleaseMemory() {
-	ReleaseBytes(n.rawBytes)
+	block, isNew := getBytesForFileBlock(r, offset, int(readSize))
+	dataSlice = block.Bytes[0:int(readSize)]
+	if isNew {
+		_, err = r.ReadAt(dataSlice, offset)
+	}
+	return dataSlice, block, err
 }
 
 func (n *Needle) ReadData(r *os.File, offset int64, size uint32, version Version) (err error) {
-	bytes, rawBytes, err := ReadNeedleBlob(r, offset, size)
-	n.rawBytes = rawBytes
+	bytes, block, err := ReadNeedleBlob(r, offset, size)
+	n.rawBlock = block
 	if err != nil {
 		return err
 	}

go/weed/weed_server/volume_server_handlers_sync.go

@@ -50,8 +50,8 @@ func (vs *VolumeServer) getVolumeDataContentHandler(w http.ResponseWriter, r *ht
 	}
 	offset := uint32(util.ParseUint64(r.FormValue("offset"), 0))
 	size := uint32(util.ParseUint64(r.FormValue("size"), 0))
-	content, rawBytes, err := storage.ReadNeedleBlob(v.DataFile(), int64(offset)*storage.NeedlePaddingSize, size)
-	defer storage.ReleaseBytes(rawBytes)
+	content, block, err := storage.ReadNeedleBlob(v.DataFile(), int64(offset)*storage.NeedlePaddingSize, size)
+	defer storage.ReleaseBytes(block.Bytes)
 	if err != nil {
 		writeJsonError(w, r, http.StatusInternalServerError, err)
 		return