mount: improve read performance on random reads

weed/filer/reader_at.go

@@ -26,6 +26,7 @@ type ChunkReadAt struct {
 	chunkCache      chunk_cache.ChunkCache
 	lastChunkFileId string
 	lastChunkData   []byte
+	readerPattern   *ReaderPattern
 }
 
 var _ = io.ReaderAt(&ChunkReadAt{})
@@ -88,10 +89,11 @@ func LookupFn(filerClient filer_pb.FilerClient) wdclient.LookupFileIdFunctionTyp
 func NewChunkReaderAtFromClient(lookupFn wdclient.LookupFileIdFunctionType, chunkViews []*ChunkView, chunkCache chunk_cache.ChunkCache, fileSize int64) *ChunkReadAt {
 
 	return &ChunkReadAt{
-		chunkViews:   chunkViews,
-		lookupFileId: lookupFn,
-		chunkCache:   chunkCache,
-		fileSize:     fileSize,
+		chunkViews:    chunkViews,
+		lookupFileId:  lookupFn,
+		chunkCache:    chunkCache,
+		fileSize:      fileSize,
+		readerPattern: NewReaderPattern(),
 	}
 }
 
@@ -106,6 +108,8 @@ func (c *ChunkReadAt) ReadAt(p []byte, offset int64) (n int, err error) {
 	c.readerLock.Lock()
 	defer c.readerLock.Unlock()
 
+	c.readerPattern.MonitorReadAt(offset, len(p))
+
 	// glog.V(4).Infof("ReadAt [%d,%d) of total file size %d bytes %d chunk views", offset, offset+int64(len(p)), c.fileSize, len(c.chunkViews))
 	return c.doReadAt(p, offset)
 }
@@ -171,6 +175,10 @@ func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
 
 func (c *ChunkReadAt) readChunkSlice(chunkView *ChunkView, nextChunkViews *ChunkView, offset, length uint64) ([]byte, error) {
 
+	if c.readerPattern.IsRandomMode() {
+		return c.doFetchRangeChunkData(chunkView, offset, length)
+	}
+
 	chunkSlice := c.chunkCache.GetChunkSlice(chunkView.FileId, offset, length)
 	if len(chunkSlice) > 0 {
 		return chunkSlice, nil
@@ -243,3 +251,15 @@ func (c *ChunkReadAt) doFetchFullChunkData(chunkView *ChunkView) ([]byte, error)
 	return data, err
 
 }
+
+func (c *ChunkReadAt) doFetchRangeChunkData(chunkView *ChunkView, offset, length uint64) ([]byte, error) {
+
+	glog.V(4).Infof("+ doFetchFullChunkData %s", chunkView.FileId)
+
+	data, err := fetchChunkRange(c.lookupFileId, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped, int64(offset), int(length))
+
+	glog.V(4).Infof("- doFetchFullChunkData %s", chunkView.FileId)
+
+	return data, err
+
+}