piecereader: Retune to allow parallel ReadAt calls

itests/deals_partial_retrieval_dm-level_test.go

@@ -48,7 +48,7 @@ func TestDMLevelPartialRetrieval(t *testing.T) {
 	ctx := context.Background()
 
 	kit.QuietMiningLogs()
-	client, miner, ens := kit.EnsembleMinimal(t, kit.ThroughRPC(), kit.MockProofs())
+	client, miner, ens := kit.EnsembleMinimal(t, kit.ThroughRPC())
 	dh := kit.NewDealHarness(t, client, miner, miner)
 	ens.InterconnectAll().BeginMining(50 * time.Millisecond)
 

storage/sealer/piece_reader.go

@@ -12,6 +12,7 @@ import (
 
 	"github.com/filecoin-project/dagstore/mount"
 	"github.com/filecoin-project/go-state-types/abi"
+	lru "github.com/hashicorp/golang-lru/v2"
 
 	"github.com/filecoin-project/lotus/metrics"
 )
@@ -21,6 +22,8 @@ import (
 var MaxPieceReaderBurnBytes int64 = 1 << 20 // 1M
 var ReadBuf = 128 * (127 * 8)               // unpadded(128k)
 
+var MinRandomReadSize = int64(4 << 10)
+
 type pieceGetter func(ctx context.Context, offset, size uint64) (io.ReadCloser, error)
 
 type pieceReader struct {
@@ -33,15 +36,27 @@ type pieceReader struct {
 	closed bool
 	seqAt  int64 // next byte to be read by io.Reader
 
-	mu  sync.Mutex
-	r   io.ReadCloser
-	br  *bufio.Reader
-	rAt int64
+	// sequential reader
+	seqMu sync.Mutex
+	r     io.ReadCloser
+	br    *bufio.Reader
+	rAt   int64
+
+	// random read cache
+	remReads *lru.Cache[int64, []byte] // data start offset -> data
+	// todo try carrying a "bytes read sequentially so far" counter with those
+	//  cacahed byte buffers, increase buffer sizes when we see that we're doing
+	//  a long sequential read
 }
 
 func (p *pieceReader) init() (_ *pieceReader, err error) {
 	stats.Record(p.ctx, metrics.DagStorePRInitCount.M(1))
 
+	p.remReads, err = lru.New[int64, []byte](100)
+	if err != nil {
+		return nil, err
+	}
+
 	p.rAt = 0
 	p.r, err = p.getReader(p.ctx, uint64(p.rAt), uint64(p.len))
 	if err != nil {
@@ -65,8 +80,8 @@ func (p *pieceReader) check() error {
 }
 
 func (p *pieceReader) Close() error {
-	p.mu.Lock()
-	defer p.mu.Unlock()
+	p.seqMu.Lock()
+	defer p.seqMu.Unlock()
 
 	if err := p.check(); err != nil {
 		return err
@@ -90,21 +105,21 @@ func (p *pieceReader) Close() error {
 }
 
 func (p *pieceReader) Read(b []byte) (int, error) {
-	p.mu.Lock()
-	defer p.mu.Unlock()
+	p.seqMu.Lock()
+	defer p.seqMu.Unlock()
 
 	if err := p.check(); err != nil {
 		return 0, err
 	}
 
-	n, err := p.readAtUnlocked(b, p.seqAt)
+	n, err := p.readSeqReader(b)
 	p.seqAt += int64(n)
 	return n, err
 }
 
 func (p *pieceReader) Seek(offset int64, whence int) (int64, error) {
-	p.mu.Lock()
-	defer p.mu.Unlock()
+	p.seqMu.Lock()
+	defer p.seqMu.Unlock()
 
 	if err := p.check(); err != nil {
 		return 0, err
@@ -124,14 +139,9 @@ func (p *pieceReader) Seek(offset int64, whence int) (int64, error) {
 	return p.seqAt, nil
 }
 
-func (p *pieceReader) ReadAt(b []byte, off int64) (n int, err error) {
-	p.mu.Lock()
-	defer p.mu.Unlock()
+func (p *pieceReader) readSeqReader(b []byte) (n int, err error) {
+	off := p.seqAt
 
-	return p.readAtUnlocked(b, off)
-}
-
-func (p *pieceReader) readAtUnlocked(b []byte, off int64) (n int, err error) {
 	if err := p.check(); err != nil {
 		return 0, err
 	}
@@ -196,4 +206,81 @@ func (p *pieceReader) readAtUnlocked(b []byte, off int64) (n int, err error) {
 	return n, err
 }
 
+func (p *pieceReader) ReadAt(b []byte, off int64) (n int, err error) {
+	var filled int64
+
+	// try to get a buf from lru
+	data, ok := p.remReads.Get(off)
+	if ok {
+		n = copy(b, data)
+		filled += int64(n)
+
+		if n < len(data) {
+			p.remReads.Add(off+int64(n), data[n:])
+
+			// keep the header buffered
+			if off != 0 {
+				p.remReads.Remove(off)
+			}
+		}
+	}
+	if filled == int64(len(b)) {
+		return n, nil
+	}
+
+	readOff := off + filled
+	readSize := int64(len(b)) - filled
+
+	smallRead := readSize < MinRandomReadSize
+
+	if smallRead {
+		// read into small read buf
+		readBuf := make([]byte, MinRandomReadSize)
+		bn, err := p.readInto(readBuf, readOff)
+		if err != nil && err != io.EOF {
+			return int(filled), err
+		}
+
+		// reslice so that the slice is the data
+		readBuf = readBuf[:bn]
+
+		// fill user data
+		used := copy(b[filled:], readBuf[:])
+		filled += int64(used)
+		readBuf = readBuf[used:]
+
+		// cache the rest
+		if len(readBuf) > 0 {
+			p.remReads.Add(readOff+int64(used), readBuf)
+		}
+	} else {
+		// read into user buf
+		bn, err := p.readInto(b[filled:], readOff)
+		if err != nil {
+			return int(filled), err
+		}
+		filled += int64(bn)
+	}
+
+	if filled < int64(len(b)) {
+		return int(filled), io.EOF
+	}
+
+	return int(filled), nil
+}
+
+func (p *pieceReader) readInto(b []byte, off int64) (n int, err error) {
+	rd, err := p.getReader(p.ctx, uint64(off), uint64(len(b)))
+	if err != nil {
+		return 0, xerrors.Errorf("getting reader: %w", err)
+	}
+
+	n, err = io.ReadFull(rd, b)
+	if err == io.ErrUnexpectedEOF {
+		err = io.EOF
+	}
+
+	return n, err
+}
+
 var _ mount.Reader = (*pieceReader)(nil)