github.com/coocood/badger@v1.5.1-0.20200528065104-c02ac3616d04/blob.go (about) 1 package badger 2 3 import ( 4 "encoding/binary" 5 "fmt" 6 "io/ioutil" 7 "math" 8 "os" 9 "path/filepath" 10 "reflect" 11 "sort" 12 "strconv" 13 "strings" 14 "sync" 15 "sync/atomic" 16 "unsafe" 17 18 "github.com/coocood/badger/epoch" 19 "github.com/coocood/badger/fileutil" 20 "github.com/coocood/badger/y" 21 "github.com/ncw/directio" 22 "github.com/pingcap/errors" 23 "github.com/pingcap/log" 24 "go.uber.org/zap" 25 ) 26 27 const blobFileSuffix = ".blob" 28 29 type blobPointer struct { 30 logicalAddr 31 length uint32 32 } 33 34 func (bp *blobPointer) decode(val []byte) { 35 ptr := (*blobPointer)(unsafe.Pointer(&val[0])) 36 *bp = *ptr 37 } 38 39 type mappingEntry struct { 40 logicalAddr 41 physicalOffset uint32 42 } 43 44 /* 45 data format of blob file: 46 / addrMappingLength(4) / addrMappingEntry(12) ... / entry ... / zero (4) / discardInfo ... / 47 48 addrMappingEntry: 49 / logicalAddr (8) / physicalOffset(4) / 50 51 logicalAddr: 52 / logicalFid(4) / logicalOffset(4) / 53 54 entry: 55 / value len(4) / value(value len) / 56 57 discard info: 58 / logicalAddr(8) ... / totalDiscard(4) / discardInfoLength(4) / 59 */ 60 type blobFile struct { 61 path string 62 fid uint32 63 fd *os.File 64 fileSize uint32 65 mappingSize uint32 66 mmap []byte 67 mappingEntries []mappingEntry 68 69 // only accessed by gcHandler 70 totalDiscard uint32 71 } 72 73 func (bf *blobFile) getID() uint32 { 74 if bf == nil { 75 return math.MaxUint32 76 } 77 return bf.fid 78 } 79 80 func (bf *blobFile) loadOffsetMap() error { 81 var headBuf [4]byte 82 _, err := bf.fd.ReadAt(headBuf[:], 0) 83 if err != nil { 84 return err 85 } 86 bf.mappingSize = binary.LittleEndian.Uint32(headBuf[:]) 87 if bf.mappingSize == 0 { 88 return nil 89 } 90 bf.mmap, err = y.Mmap(bf.fd, false, int64(bf.mappingSize)) 91 if err != nil { 92 return err 93 } 94 hdr := (*reflect.SliceHeader)(unsafe.Pointer(&bf.mappingEntries)) 95 hdr.Len = int(bf.mappingSize-4) / 12 96 hdr.Cap = hdr.Len 97 hdr.Data = uintptr(unsafe.Pointer(&bf.mmap[4])) 98 return nil 99 } 100 101 func (bf *blobFile) loadDiscards() error { 102 var footBuf [8]byte 103 _, err := bf.fd.ReadAt(footBuf[:], int64(bf.fileSize-8)) 104 if err != nil { 105 return err 106 } 107 bf.totalDiscard = binary.LittleEndian.Uint32(footBuf[:]) 108 return nil 109 } 110 111 func (bf *blobFile) read(bp blobPointer, s *y.Slice) (buf []byte, err error) { 112 physicalOff := int64(bf.getPhysicalOffset(bp.logicalAddr)) 113 buf = s.Resize(int(bp.length)) 114 _, err = bf.fd.ReadAt(buf, physicalOff) // skip the 4 bytes length. 115 return buf, err 116 } 117 118 func (bf *blobFile) getPhysicalOffset(addr logicalAddr) uint32 { 119 if bf.fid == addr.fid { 120 return addr.offset 121 } 122 n := sort.Search(len(bf.mappingEntries), func(i int) bool { 123 entry := bf.mappingEntries[i] 124 return !entry.logicalAddr.Less(addr) 125 }) 126 return bf.mappingEntries[n].physicalOffset 127 } 128 129 func (bf *blobFile) Delete() error { 130 if bf.mmap != nil { 131 y.Munmap(bf.mmap) 132 } 133 bf.fd.Close() 134 return os.Remove(bf.path) 135 } 136 137 type blobFileBuilder struct { 138 fid uint32 139 file *os.File 140 writer *fileutil.DirectWriter 141 } 142 143 func newBlobFileBuilder(fid uint32, dir string, writeBufferSize int) (*blobFileBuilder, error) { 144 fileName := newBlobFileName(fid, dir) 145 file, err := directio.OpenFile(fileName, os.O_CREATE|os.O_RDWR, 0666) 146 if err != nil { 147 return nil, err 148 } 149 writer := fileutil.NewDirectWriter(file, writeBufferSize, nil) 150 // Write 4 bytes 0 header. 151 err = writer.Append(make([]byte, 4)) 152 if err != nil { 153 return nil, err 154 } 155 return &blobFileBuilder{ 156 fid: uint32(fid), 157 file: file, 158 writer: writer, 159 }, nil 160 } 161 162 func (bfb *blobFileBuilder) append(value []byte) (bp []byte, err error) { 163 var lenBuf [4]byte 164 binary.LittleEndian.PutUint32(lenBuf[:], uint32(len(value))) 165 err = bfb.writer.Append(lenBuf[:]) 166 if err != nil { 167 return 168 } 169 offset := uint32(bfb.writer.Offset()) 170 err = bfb.writer.Append(value) 171 if err != nil { 172 return 173 } 174 bp = make([]byte, 12) 175 binary.LittleEndian.PutUint32(bp, bfb.fid) 176 binary.LittleEndian.PutUint32(bp[4:], offset) 177 binary.LittleEndian.PutUint32(bp[8:], uint32(len(value))) 178 return 179 } 180 181 func (bfb *blobFileBuilder) finish() (*blobFile, error) { 182 // Write 4 bytes footer 183 err := bfb.writer.Append(make([]byte, 4)) 184 if err != nil { 185 return nil, err 186 } 187 err = bfb.writer.Finish() 188 if err != nil { 189 return nil, err 190 } 191 _ = bfb.file.Close() 192 return newBlobFile(bfb.file.Name(), bfb.fid, uint32(bfb.writer.Offset())) 193 } 194 195 func newBlobFile(path string, fid, fileSize uint32) (*blobFile, error) { 196 file, err := os.OpenFile(path, os.O_RDWR, 0666) 197 if err != nil { 198 return nil, err 199 } 200 _, err = file.Seek(0, 2) 201 if err != nil { 202 return nil, err 203 } 204 return &blobFile{ 205 path: path, 206 fid: fid, 207 fd: file, 208 fileSize: fileSize, 209 }, nil 210 } 211 212 func newBlobFileName(id uint32, dir string) string { 213 return filepath.Join(dir, fmt.Sprintf("%08x", id)+blobFileSuffix) 214 } 215 216 type blobManager struct { 217 filesLock sync.RWMutex 218 physicalFiles map[uint32]*blobFile 219 logicalToPhysical map[uint32]uint32 // maps logical fid to physical fid. 220 changeLog *os.File 221 dirPath string 222 kv *DB 223 discardCh chan<- *DiscardStats 224 maxFileID uint32 225 } 226 227 func (bm *blobManager) Open(kv *DB, opt Options) error { 228 bm.physicalFiles = map[uint32]*blobFile{} 229 bm.dirPath = opt.ValueDir 230 bm.kv = kv 231 validFids, err := bm.loadChangeLogs() 232 if err != nil { 233 return err 234 } 235 fileInfos, err := ioutil.ReadDir(bm.dirPath) 236 if err != nil { 237 return errors.Wrapf(err, "Error while opening blob files") 238 } 239 for _, fileInfo := range fileInfos { 240 if !strings.HasSuffix(fileInfo.Name(), ".blob") { 241 continue 242 } 243 fsz := len(fileInfo.Name()) 244 fid64, err := strconv.ParseUint(fileInfo.Name()[:fsz-5], 16, 64) 245 if err != nil { 246 return errors.Wrapf(err, "Error while parsing blob file id for file: %q", fileInfo.Name()) 247 } 248 fid := uint32(fid64) 249 path := filepath.Join(bm.dirPath, fileInfo.Name()) 250 if _, ok := validFids[fid]; !ok { 251 _ = os.Remove(path) 252 continue 253 } 254 if _, ok := bm.physicalFiles[fid]; ok { 255 return errors.Errorf("Found the same blob file twice: %d", fid) 256 } 257 blobFile, err := newBlobFile(path, fid, uint32(fileInfo.Size())) 258 if err != nil { 259 return err 260 } 261 err = blobFile.loadOffsetMap() 262 if err != nil { 263 return err 264 } 265 err = blobFile.loadDiscards() 266 if err != nil { 267 return err 268 } 269 bm.physicalFiles[fid] = blobFile 270 } 271 for _, to := range bm.logicalToPhysical { 272 if _, ok := bm.physicalFiles[to]; !ok { 273 return errors.Errorf("File %d not found", to) 274 } 275 } 276 discardCh := make(chan *DiscardStats, 1024) 277 bm.discardCh = discardCh 278 gcHandler := &blobGCHandler{ 279 bm: bm, 280 discardCh: discardCh, 281 gcCandidate: map[*blobFile]struct{}{}, 282 physicalCache: make(map[uint32]*blobFile, len(bm.physicalFiles)), 283 logicalToPhysical: map[uint32]uint32{}, 284 } 285 for k, v := range bm.logicalToPhysical { 286 gcHandler.logicalToPhysical[k] = v 287 } 288 for k, v := range bm.physicalFiles { 289 gcHandler.physicalCache[k] = v 290 } 291 kv.closers.blobManager = y.NewCloser(1) 292 go gcHandler.run(kv.closers.blobManager) 293 return nil 294 } 295 296 func (bm *blobManager) allocFileID() uint32 { 297 return atomic.AddUint32(&bm.maxFileID, 1) 298 } 299 300 func (bm *blobManager) read(ptr []byte, s *y.Slice, cache map[uint32]*blobCache) ([]byte, error) { 301 var bp blobPointer 302 bp.decode(ptr) 303 bc, ok := cache[bp.fid] 304 if !ok { 305 bf := bm.getFile(bp.fid) 306 bc = &blobCache{ 307 file: bf, 308 } 309 cache[bf.fid] = bc 310 } 311 return bc.read(bp, s) 312 } 313 314 func (bm *blobManager) getFile(fid uint32) *blobFile { 315 bm.filesLock.RLock() 316 file, ok := bm.physicalFiles[fid] 317 if !ok { 318 var physicalID uint32 319 physicalID, ok = bm.logicalToPhysical[fid] 320 if ok { 321 file = bm.physicalFiles[physicalID] 322 } 323 } 324 if file == nil { 325 log.Error("failed to get file", zap.Uint32("id", fid)) 326 } 327 bm.filesLock.RUnlock() 328 return file 329 } 330 331 func (bm *blobManager) addFile(file *blobFile) error { 332 buf := make([]byte, 8) 333 binary.LittleEndian.PutUint32(buf, file.fid) 334 binary.LittleEndian.PutUint32(buf[4:], file.fid) 335 _, err := bm.changeLog.Write(buf) 336 if err != nil { 337 return err 338 } 339 err = bm.changeLog.Sync() 340 if err != nil { 341 return err 342 } 343 bm.filesLock.Lock() 344 bm.physicalFiles[file.fid] = file 345 bm.filesLock.Unlock() 346 return nil 347 } 348 349 func (bm *blobManager) addGCFile(oldFiles []*blobFile, newFile *blobFile, logicalFiles map[uint32]struct{}, guard *epoch.Guard) error { 350 oldFids := make([]uint32, len(oldFiles)) 351 for i, v := range oldFiles { 352 oldFids[i] = v.fid 353 } 354 log.Info("addGCFile", zap.Uint32s("old files", oldFids), zap.Uint32("new file id", newFile.getID()), zap.String("logical files", fmt.Sprintf("%v", logicalFiles))) 355 buf := make([]byte, len(oldFiles)*8) 356 for i, oldFile := range oldFiles { 357 offset := i * 8 358 binary.LittleEndian.PutUint32(buf[offset:], oldFile.fid) 359 binary.LittleEndian.PutUint32(buf[offset+4:], newFile.getID()) 360 } 361 _, err := bm.changeLog.Write(buf) 362 if err != nil { 363 return err 364 } 365 err = bm.changeLog.Sync() 366 if err != nil { 367 return err 368 } 369 bm.filesLock.Lock() 370 if newFile != nil { 371 bm.physicalFiles[newFile.fid] = newFile 372 for logicalFid := range logicalFiles { 373 bm.logicalToPhysical[logicalFid] = newFile.fid 374 } 375 } else { 376 for logicalFid := range logicalFiles { 377 delete(bm.logicalToPhysical, logicalFid) 378 } 379 } 380 for _, old := range oldFiles { 381 delete(bm.physicalFiles, old.fid) 382 } 383 bm.filesLock.Unlock() 384 del := make([]epoch.Resource, len(oldFids)) 385 for i := range oldFiles { 386 del[i] = oldFiles[i] 387 } 388 guard.Delete(del) 389 return nil 390 } 391 392 type fidNode struct { 393 fid uint32 394 next *fidNode 395 } 396 397 func (bm *blobManager) loadChangeLogs() (validFids map[uint32]struct{}, err error) { 398 changeLogFileName := filepath.Join(bm.dirPath, "blob_change.log") 399 data, err := ioutil.ReadFile(changeLogFileName) 400 if err != nil && !os.IsNotExist(err) { 401 return nil, err 402 } 403 validFids = bm.buildLogicalToPhysical(data) 404 bm.changeLog, err = os.OpenFile(changeLogFileName, os.O_CREATE|os.O_RDWR, 0666) 405 if err != nil { 406 return nil, err 407 } 408 _, err = bm.changeLog.Seek(0, 2) 409 if err != nil { 410 return nil, err 411 } 412 return validFids, nil 413 } 414 415 func (bm *blobManager) buildLogicalToPhysical(data []byte) (validFids map[uint32]struct{}) { 416 changeLogMap := map[uint32]uint32{} // maps old fid to a new fid. 417 logicalFids := map[uint32]struct{}{} 418 for i := 0; i < len(data); i += 8 { 419 fromFid := binary.LittleEndian.Uint32(data[i:]) 420 toFid := binary.LittleEndian.Uint32(data[i+4:]) 421 changeLogMap[fromFid] = toFid 422 if fromFid == toFid { 423 logicalFids[fromFid] = struct{}{} 424 } 425 } 426 bm.logicalToPhysical = map[uint32]uint32{} 427 validFids = map[uint32]struct{}{} 428 for fid := range logicalFids { 429 toFid := getToFid(changeLogMap, fid) 430 if toFid != math.MaxUint32 { 431 bm.logicalToPhysical[fid] = toFid 432 validFids[toFid] = struct{}{} 433 if bm.maxFileID < toFid { 434 bm.maxFileID = toFid 435 } 436 } 437 } 438 return 439 } 440 441 func getToFid(logicalMap map[uint32]uint32, toFid uint32) uint32 { 442 for { 443 nextToFid, ok := logicalMap[toFid] 444 if !ok { 445 return toFid 446 } 447 if nextToFid == toFid { 448 return toFid 449 } 450 toFid = nextToFid 451 } 452 } 453 454 type blobGCHandler struct { 455 bm *blobManager 456 discardCh <-chan *DiscardStats 457 physicalCache map[uint32]*blobFile 458 logicalToPhysical map[uint32]uint32 459 460 gcCandidate map[*blobFile]struct{} 461 candidateValidSize uint32 462 candidateDiscardSize uint64 463 } 464 465 func (h *blobGCHandler) run(c *y.Closer) { 466 defer c.Done() 467 for { 468 select { 469 case discardInfo := <-h.discardCh: 470 h.handleDiscardInfo(discardInfo) 471 err := h.doGCIfNeeded() 472 if err != nil { 473 log.Error("handle discardInfo", zap.Error(err)) 474 } 475 case <-c.HasBeenClosed(): 476 return 477 } 478 } 479 } 480 481 func (h *blobGCHandler) handleDiscardInfo(discardStats *DiscardStats) { 482 physicalDiscards := make(map[uint32][]blobPointer) 483 for _, ptr := range discardStats.ptrs { 484 physicalFid := h.getLogicalToPhysical(ptr.fid) 485 ptrs := physicalDiscards[physicalFid] 486 physicalDiscards[physicalFid] = append(ptrs, ptr) 487 } 488 for physicalFid, ptrs := range physicalDiscards { 489 err := h.writeDiscardToFile(physicalFid, ptrs) 490 if err != nil { 491 log.Error("handleDiscardInfo", zap.Uint32("physicalFid", physicalFid), zap.Error(err)) 492 continue 493 } 494 } 495 } 496 497 func (h *blobGCHandler) getPhysicalFile(physicalFid uint32) *blobFile { 498 file := h.physicalCache[physicalFid] 499 if file == nil { 500 file = h.bm.getFile(physicalFid) 501 h.physicalCache[physicalFid] = file 502 } 503 return file 504 } 505 506 func (h *blobGCHandler) getLogicalToPhysical(logicalFid uint32) uint32 { 507 physicalFid, ok := h.logicalToPhysical[logicalFid] 508 if !ok { 509 // must be newly added L0 blob 510 h.logicalToPhysical[logicalFid] = logicalFid 511 physicalFid = logicalFid 512 } 513 return physicalFid 514 } 515 516 func (h *blobGCHandler) writeDiscardToFile(physicalFid uint32, ptrs []blobPointer) error { 517 file := h.getPhysicalFile(physicalFid) 518 discardInfo := make([]byte, uint32(len(ptrs)*8+8)) 519 totalDiscard := file.totalDiscard + uint32(len(discardInfo)) 520 for i, ptr := range ptrs { 521 binary.LittleEndian.PutUint32(discardInfo[i*8:], ptr.fid) 522 binary.LittleEndian.PutUint32(discardInfo[i*8+4:], ptr.offset) 523 totalDiscard += ptr.length 524 } 525 binary.LittleEndian.PutUint32(discardInfo[len(discardInfo)-8:], totalDiscard) 526 binary.LittleEndian.PutUint32(discardInfo[len(discardInfo)-4:], uint32(len(discardInfo))) 527 _, err := file.fd.Write(discardInfo) 528 if err != nil { 529 return err 530 } 531 file.totalDiscard = totalDiscard 532 file.fileSize += uint32(len(discardInfo)) 533 if file.totalDiscard > file.fileSize/2 { 534 h.gcCandidate[file] = struct{}{} 535 h.candidateValidSize += file.fileSize - file.mappingSize - file.totalDiscard 536 h.candidateDiscardSize += uint64(file.totalDiscard) 537 } 538 return nil 539 } 540 541 var ( 542 minCandidateValidSize uint32 = 32 * 1024 * 1024 543 maxCandidateValidSize uint32 = 128 * 1024 * 1024 544 maxCandidateDiscardSize uint64 = 512 * 1024 * 1024 545 ) 546 547 func (h *blobGCHandler) doGCIfNeeded() error { 548 guard := h.bm.kv.resourceMgr.Acquire() 549 defer guard.Done() 550 551 if len(h.gcCandidate) == 0 { 552 return nil 553 } 554 if h.candidateValidSize < minCandidateValidSize && h.candidateDiscardSize < maxCandidateDiscardSize { 555 return nil 556 } 557 var oldFiles []*blobFile 558 var totalValidSize uint32 559 for candidate := range h.gcCandidate { 560 validSize := candidate.fileSize - candidate.mappingSize - candidate.totalDiscard 561 if totalValidSize+validSize > maxCandidateValidSize { 562 break 563 } 564 totalValidSize += validSize 565 oldFiles = append(oldFiles, candidate) 566 delete(h.gcCandidate, candidate) 567 } 568 var validEntries []validEntry 569 for _, blobFile := range oldFiles { 570 blobBytes, err := ioutil.ReadFile(blobFile.path) 571 if err != nil { 572 return err 573 } 574 validEntries = h.extractValidEntries(validEntries, blobFile, blobBytes) 575 } 576 if len(validEntries) == 0 { 577 for _, oldFile := range oldFiles { 578 delete(h.physicalCache, oldFile.fid) 579 } 580 return h.bm.addGCFile(oldFiles, nil, nil, guard) 581 } 582 sort.Slice(validEntries, func(i, j int) bool { 583 return validEntries[i].logicalAddr.Less(validEntries[j].logicalAddr) 584 }) 585 newFid := h.bm.allocFileID() 586 fileName := newBlobFileName(newFid, h.bm.kv.opt.Dir) 587 file, err := directio.OpenFile(fileName, os.O_CREATE|os.O_RDWR, 0666) 588 if err != nil { 589 return err 590 } 591 writer := fileutil.NewDirectWriter(file, 1024*1024, nil) 592 // 4 bytes addrMapping length 593 mappingSize := 4 + uint32(len(validEntries))*12 594 lenBuf := make([]byte, 4) 595 binary.LittleEndian.PutUint32(lenBuf, mappingSize) 596 err = writer.Append(lenBuf) 597 if err != nil { 598 return err 599 } 600 mappingEntryBuf := make([]byte, 12) 601 newOffset := 4 + uint32(len(validEntries))*12 + 4 602 logicalFids := make(map[uint32]struct{}) 603 for _, entry := range validEntries { 604 logicalFids[entry.fid] = struct{}{} 605 binary.LittleEndian.PutUint32(mappingEntryBuf, entry.fid) 606 binary.LittleEndian.PutUint32(mappingEntryBuf[4:], entry.offset) 607 binary.LittleEndian.PutUint32(mappingEntryBuf[8:], newOffset) 608 newOffset += uint32(len(entry.value)) + 4 609 err = writer.Append(mappingEntryBuf) 610 if err != nil { 611 return err 612 } 613 } 614 for _, entry := range validEntries { 615 binary.LittleEndian.PutUint32(lenBuf, uint32(len(entry.value))) 616 err = writer.Append(lenBuf) 617 if err != nil { 618 return err 619 } 620 err = writer.Append(entry.value) 621 if err != nil { 622 return err 623 } 624 } 625 // 4 bytes 0 discard length 626 err = writer.Append(make([]byte, 4)) 627 if err != nil { 628 return err 629 } 630 err = writer.Finish() 631 if err != nil { 632 return err 633 } 634 file.Close() 635 blobFile, err := newBlobFile(file.Name(), newFid, uint32(writer.Offset())) 636 if err != nil { 637 return err 638 } 639 err = blobFile.loadOffsetMap() 640 if err != nil { 641 return err 642 } 643 h.physicalCache[newFid] = blobFile 644 for _, oldFile := range oldFiles { 645 delete(h.physicalCache, oldFile.fid) 646 } 647 for logicalFid := range logicalFids { 648 h.logicalToPhysical[logicalFid] = newFid 649 } 650 return h.bm.addGCFile(oldFiles, blobFile, logicalFids, guard) 651 } 652 653 type logicalAddr struct { 654 fid uint32 655 offset uint32 656 } 657 658 func (a logicalAddr) Less(b logicalAddr) bool { 659 if a.fid == b.fid { 660 return a.offset < b.offset 661 } 662 return a.fid < b.fid 663 } 664 665 type validEntry struct { 666 logicalAddr 667 value []byte 668 } 669 670 func (h *blobGCHandler) extractValidEntries(validEntries []validEntry, file *blobFile, blobBytes []byte) []validEntry { 671 physicalToLogical := make(map[uint32]logicalAddr, len(file.mappingEntries)) 672 for _, mappingEntry := range file.mappingEntries { 673 physicalToLogical[mappingEntry.physicalOffset] = mappingEntry.logicalAddr 674 } 675 discardedPhysicalOffsets, endOff := h.buildDiscardPhysicalOffsets(file, blobBytes) 676 cursor := file.mappingSize 677 for cursor < endOff { 678 valLen := binary.LittleEndian.Uint32(blobBytes[cursor:]) 679 cursor += 4 680 physicalOff := cursor 681 cursor += valLen 682 _, isDiscarded := discardedPhysicalOffsets[physicalOff] 683 if isDiscarded { 684 continue 685 } 686 var logical logicalAddr 687 if len(file.mappingEntries) == 0 { 688 logical.fid = file.fid 689 logical.offset = physicalOff 690 } else { 691 logical = physicalToLogical[physicalOff] 692 } 693 validEntries = append(validEntries, validEntry{ 694 value: blobBytes[physicalOff : physicalOff+valLen], 695 logicalAddr: logical, 696 }) 697 } 698 return validEntries 699 } 700 701 func (h *blobGCHandler) buildDiscardPhysicalOffsets(file *blobFile, blobBytes []byte) (discards map[uint32]struct{}, endOff uint32) { 702 discards = make(map[uint32]struct{}) 703 blobBytesOff := uint32(len(blobBytes)) 704 for { 705 discardLength := binary.LittleEndian.Uint32(blobBytes[blobBytesOff-4:]) 706 if discardLength == 0 { 707 break 708 } 709 discardAddrs := blobBytes[blobBytesOff-discardLength : blobBytesOff-8] 710 blobBytesOff -= discardLength 711 for i := 0; i < len(discardAddrs); i += 8 { 712 var addr logicalAddr 713 addr.fid = binary.LittleEndian.Uint32(discardAddrs[i:]) 714 addr.offset = binary.LittleEndian.Uint32(discardAddrs[i+4:]) 715 physicalOffset := file.getPhysicalOffset(addr) 716 discards[physicalOffset] = struct{}{} 717 } 718 } 719 return discards, blobBytesOff 720 } 721 722 type blobCache struct { 723 file *blobFile 724 cacheData []byte 725 cacheOffset uint32 726 lastPhysical uint32 727 } 728 729 const cacheSize = 8 * 1024 730 731 func (bc *blobCache) read(bp blobPointer, slice *y.Slice) ([]byte, error) { 732 physicalOffset := bc.file.getPhysicalOffset(bp.logicalAddr) 733 lastPhysical := bc.lastPhysical 734 bc.lastPhysical = physicalOffset 735 if lastPhysical == 0 || bp.length > cacheSize { 736 return bc.file.read(bp, slice) 737 } 738 if physicalOffset >= bc.cacheOffset && physicalOffset+bp.length < bc.cacheOffset+uint32(len(bc.cacheData)) { 739 off := physicalOffset - bc.cacheOffset 740 return bc.cacheData[off : off+bp.length], nil 741 } 742 if bc.cacheData == nil { 743 bc.cacheData = make([]byte, cacheSize) 744 } 745 readLen := uint32(len(bc.cacheData)) 746 if readLen > bc.file.fileSize-physicalOffset { 747 readLen = bc.file.fileSize - physicalOffset 748 } 749 _, err := bc.file.fd.ReadAt(bc.cacheData[:readLen], int64(physicalOffset)) 750 if err != nil { 751 return nil, err 752 } 753 bc.cacheOffset = physicalOffset 754 return bc.cacheData[:bp.length], nil 755 }