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mount: adds read prefetching

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This commit is contained in:
Chris Lu 2020-10-03 16:50:09 -07:00
parent 707936f482
commit 692f0614d1
1 changed files with 33 additions and 6 deletions
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39
weed/filer/reader_at.go
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@ -19,7 +19,10 @@ type ChunkReadAt struct {
readerLock sync.Mutex readerLock sync.Mutex
fileSize int64 fileSize int64
chunkCache chunk_cache.ChunkCache lastChunkFileId string
lastChunkData []byte
isPrefetching bool
chunkCache chunk_cache.ChunkCache
} }
// var _ = io.ReaderAt(&ChunkReadAt{}) // var _ = io.ReaderAt(&ChunkReadAt{})
@ -76,10 +79,16 @@ func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
var buffer []byte var buffer []byte
startOffset, remaining := offset, int64(len(p)) startOffset, remaining := offset, int64(len(p))
var nextChunkView *ChunkView
for i, chunk := range c.chunkViews { for i, chunk := range c.chunkViews {
if remaining <= 0 { if remaining <= 0 {
break break
} }
if i+1 < len(c.chunkViews) {
nextChunkView = c.chunkViews[i+1]
} else {
nextChunkView = nil
}
if startOffset < chunk.LogicOffset { if startOffset < chunk.LogicOffset {
gap := int(chunk.LogicOffset - startOffset) gap := int(chunk.LogicOffset - startOffset)
glog.V(4).Infof("zero [%d,%d)", startOffset, startOffset+int64(gap)) glog.V(4).Infof("zero [%d,%d)", startOffset, startOffset+int64(gap))
@ -95,7 +104,7 @@ func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
continue continue
} }
glog.V(4).Infof("read [%d,%d), %d/%d chunk %s [%d,%d)", chunkStart, chunkStop, i, len(c.chunkViews), chunk.FileId, chunk.LogicOffset-chunk.Offset, chunk.LogicOffset-chunk.Offset+int64(chunk.Size)) glog.V(4).Infof("read [%d,%d), %d/%d chunk %s [%d,%d)", chunkStart, chunkStop, i, len(c.chunkViews), chunk.FileId, chunk.LogicOffset-chunk.Offset, chunk.LogicOffset-chunk.Offset+int64(chunk.Size))
buffer, err = c.readFromWholeChunkData(chunk) buffer, err = c.readFromWholeChunkData(chunk, nextChunkView)
if err != nil { if err != nil {
glog.Errorf("fetching chunk %+v: %v\n", chunk, err) glog.Errorf("fetching chunk %+v: %v\n", chunk, err)
return return
@ -123,27 +132,45 @@ func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
} }
func (c *ChunkReadAt) readFromWholeChunkData(chunkView *ChunkView) (chunkData []byte, err error) { func (c *ChunkReadAt) readFromWholeChunkData(chunkView *ChunkView, nextChunkView *ChunkView) (chunkData []byte, err error) {
glog.V(4).Infof("readFromWholeChunkData %s offset %d [%d,%d) size at least %d", chunkView.FileId, chunkView.Offset, chunkView.LogicOffset, chunkView.LogicOffset+int64(chunkView.Size), chunkView.ChunkSize) glog.V(4).Infof("readFromWholeChunkData %s offset %d [%d,%d) size at least %d", chunkView.FileId, chunkView.Offset, chunkView.LogicOffset, chunkView.LogicOffset+int64(chunkView.Size), chunkView.ChunkSize)
if c.lastChunkFileId == chunkView.FileId {
return c.lastChunkData, nil
}
chunkData = c.chunkCache.GetChunk(chunkView.FileId, chunkView.ChunkSize) chunkData = c.chunkCache.GetChunk(chunkView.FileId, chunkView.ChunkSize)
if chunkData != nil { if chunkData != nil {
glog.V(4).Infof("cache hit %s [%d,%d)", chunkView.FileId, chunkView.LogicOffset-chunkView.Offset, chunkView.LogicOffset-chunkView.Offset+int64(len(chunkData))) glog.V(4).Infof("cache hit %s [%d,%d)", chunkView.FileId, chunkView.LogicOffset-chunkView.Offset, chunkView.LogicOffset-chunkView.Offset+int64(len(chunkData)))
} else { } else {
glog.V(4).Infof("doFetchFullChunkData %s", chunkView.FileId) glog.V(4).Infof("doFetchFullChunkData %s", chunkView.FileId)
chunkData, err = c.doFetchFullChunkData(chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped) chunkData, err = c.doFetchFullChunkData(chunkView)
if err != nil { if err != nil {
return return
} }
c.chunkCache.SetChunk(chunkView.FileId, chunkData) c.chunkCache.SetChunk(chunkView.FileId, chunkData)
} }
c.lastChunkData = chunkData
c.lastChunkFileId = chunkView.FileId
if nextChunkView != nil && !c.isPrefetching {
c.isPrefetching = true
go func() {
if chunkData, err := c.doFetchFullChunkData(nextChunkView); err == nil {
c.chunkCache.SetChunk(nextChunkView.FileId, chunkData)
}
c.isPrefetching = false
}()
}
return return
} }
func (c *ChunkReadAt) doFetchFullChunkData(fileId string, cipherKey []byte, isGzipped bool) ([]byte, error) { func (c *ChunkReadAt) doFetchFullChunkData(chunkView *ChunkView) ([]byte, error) {
return fetchChunk(c.lookupFileId, fileId, cipherKey, isGzipped) data, err := fetchChunk(c.lookupFileId, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped)
return data, err
} }