package torrent import ( "container/heap" "context" "encoding/gob" "fmt" "reflect" "runtime/pprof" "time" "unsafe" "github.com/anacrolix/log" "github.com/anacrolix/multiless" request_strategy "github.com/anacrolix/torrent/request-strategy" ) func (t *Torrent) requestStrategyPieceOrderState(i int) request_strategy.PieceRequestOrderState { return request_strategy.PieceRequestOrderState{ Priority: t.piece(i).purePriority(), Partial: t.piecePartiallyDownloaded(i), Availability: t.piece(i).availability(), } } func init() { gob.Register(peerId{}) } type peerId struct { *Peer ptr uintptr } func (p peerId) Uintptr() uintptr { return p.ptr } func (p peerId) GobEncode() (b []byte, _ error) { *(*reflect.SliceHeader)(unsafe.Pointer(&b)) = reflect.SliceHeader{ Data: uintptr(unsafe.Pointer(&p.ptr)), Len: int(unsafe.Sizeof(p.ptr)), Cap: int(unsafe.Sizeof(p.ptr)), } return } func (p *peerId) GobDecode(b []byte) error { if uintptr(len(b)) != unsafe.Sizeof(p.ptr) { panic(len(b)) } ptr := unsafe.Pointer(&b[0]) p.ptr = *(*uintptr)(ptr) log.Printf("%p", ptr) dst := reflect.SliceHeader{ Data: uintptr(unsafe.Pointer(&p.Peer)), Len: int(unsafe.Sizeof(p.Peer)), Cap: int(unsafe.Sizeof(p.Peer)), } copy(*(*[]byte)(unsafe.Pointer(&dst)), b) return nil } type ( RequestIndex = request_strategy.RequestIndex chunkIndexType = request_strategy.ChunkIndex ) type peerRequests struct { requestIndexes []RequestIndex peer *Peer } func (p *peerRequests) Len() int { return len(p.requestIndexes) } func (p *peerRequests) Less(i, j int) bool { leftRequest := p.requestIndexes[i] rightRequest := p.requestIndexes[j] t := p.peer.t leftPieceIndex := leftRequest / t.chunksPerRegularPiece() rightPieceIndex := rightRequest / t.chunksPerRegularPiece() ml := multiless.New() // Push requests that can't be served right now to the end. But we don't throw them away unless // there's a better alternative. This is for when we're using the fast extension and get choked // but our requests could still be good when we get unchoked. if p.peer.peerChoking { ml = ml.Bool( !p.peer.peerAllowedFast.Contains(leftPieceIndex), !p.peer.peerAllowedFast.Contains(rightPieceIndex), ) } leftPiece := t.piece(int(leftPieceIndex)) rightPiece := t.piece(int(rightPieceIndex)) // Putting this first means we can steal requests from lesser-performing peers for our first few // new requests. ml = ml.Int( // Technically we would be happy with the cached priority here, except we don't actually // cache it anymore, and Torrent.piecePriority just does another lookup of *Piece to resolve // the priority through Piece.purePriority, which is probably slower. -int(leftPiece.purePriority()), -int(rightPiece.purePriority()), ) leftPeer := t.pendingRequests[leftRequest] rightPeer := t.pendingRequests[rightRequest] ml = ml.Bool(rightPeer == p.peer, leftPeer == p.peer) ml = ml.Bool(rightPeer == nil, leftPeer == nil) if ml.Ok() { return ml.MustLess() } if leftPeer != nil { // The right peer should also be set, or we'd have resolved the computation by now. ml = ml.Uint64( rightPeer.requestState.Requests.GetCardinality(), leftPeer.requestState.Requests.GetCardinality(), ) // Could either of the lastRequested be Zero? That's what checking an existing peer is for. leftLast := t.lastRequested[leftRequest] rightLast := t.lastRequested[rightRequest] if leftLast.IsZero() || rightLast.IsZero() { panic("expected non-zero last requested times") } // We want the most-recently requested on the left. Clients like Transmission serve requests // in received order, so the most recently-requested is the one that has the longest until // it will be served and therefore is the best candidate to cancel. ml = ml.CmpInt64(rightLast.Sub(leftLast).Nanoseconds()) } ml = ml.Int( int(leftPiece.relativeAvailability), int(rightPiece.relativeAvailability)) return ml.Less() } func (p *peerRequests) Swap(i, j int) { p.requestIndexes[i], p.requestIndexes[j] = p.requestIndexes[j], p.requestIndexes[i] } func (p *peerRequests) Push(x interface{}) { p.requestIndexes = append(p.requestIndexes, x.(RequestIndex)) } func (p *peerRequests) Pop() interface{} { last := len(p.requestIndexes) - 1 x := p.requestIndexes[last] p.requestIndexes = p.requestIndexes[:last] return x } type desiredRequestState struct { Requests peerRequests Interested bool } func (p *Peer) getDesiredRequestState() (desired desiredRequestState) { if !p.t.haveInfo() { return } if p.t.closed.IsSet() { return } input := p.t.getRequestStrategyInput() requestHeap := peerRequests{ peer: p, } request_strategy.GetRequestablePieces( input, p.t.getPieceRequestOrder(), func(ih InfoHash, pieceIndex int) { if ih != p.t.infoHash { return } if !p.peerHasPiece(pieceIndex) { return } allowedFast := p.peerAllowedFast.ContainsInt(pieceIndex) p.t.piece(pieceIndex).undirtiedChunksIter.Iter(func(ci request_strategy.ChunkIndex) { r := p.t.pieceRequestIndexOffset(pieceIndex) + ci if !allowedFast { // We must signal interest to request this. TODO: We could set interested if the // peers pieces (minus the allowed fast set) overlap with our missing pieces if // there are any readers, or any pending pieces. desired.Interested = true // We can make or will allow sustaining a request here if we're not choked, or // have made the request previously (presumably while unchoked), and haven't had // the peer respond yet (and the request was retained because we are using the // fast extension). if p.peerChoking && !p.requestState.Requests.Contains(r) { // We can't request this right now. return } } if p.requestState.Cancelled.Contains(r) { // Can't re-request while awaiting acknowledgement. return } requestHeap.requestIndexes = append(requestHeap.requestIndexes, r) }) }, ) p.t.assertPendingRequests() desired.Requests = requestHeap return } func (p *Peer) maybeUpdateActualRequestState() { if p.closed.IsSet() { return } if p.needRequestUpdate == "" { return } if p.needRequestUpdate == peerUpdateRequestsTimerReason { since := time.Since(p.lastRequestUpdate) if since < updateRequestsTimerDuration { panic(since) } } pprof.Do( context.Background(), pprof.Labels("update request", p.needRequestUpdate), func(_ context.Context) { next := p.getDesiredRequestState() p.applyRequestState(next) }, ) } // Transmit/action the request state to the peer. func (p *Peer) applyRequestState(next desiredRequestState) { current := &p.requestState if !p.setInterested(next.Interested) { panic("insufficient write buffer") } more := true requestHeap := &next.Requests t := p.t originalRequestCount := current.Requests.GetCardinality() // We're either here on a timer, or because we ran out of requests. Both are valid reasons to // alter peakRequests. if originalRequestCount != 0 && p.needRequestUpdate != peerUpdateRequestsTimerReason { panic(fmt.Sprintf( "expected zero existing requests (%v) for update reason %q", originalRequestCount, p.needRequestUpdate)) } heap.Init(requestHeap) for requestHeap.Len() != 0 && maxRequests(current.Requests.GetCardinality()+current.Cancelled.GetCardinality()) < p.nominalMaxRequests() { req := heap.Pop(requestHeap).(RequestIndex) existing := t.requestingPeer(req) if existing != nil && existing != p { // Don't steal from the poor. diff := int64(current.Requests.GetCardinality()) + 1 - (int64(existing.uncancelledRequests()) - 1) // Steal a request that leaves us with one more request than the existing peer // connection if the stealer more recently received a chunk. if diff > 1 || (diff == 1 && p.lastUsefulChunkReceived.Before(existing.lastUsefulChunkReceived)) { continue } t.cancelRequest(req) } more = p.mustRequest(req) if !more { break } } if !more { // This might fail if we incorrectly determine that we can fit up to the maximum allowed // requests into the available write buffer space. We don't want that to happen because it // makes our peak requests dependent on how much was already in the buffer. panic(fmt.Sprintf( "couldn't fill apply entire request state [newRequests=%v]", current.Requests.GetCardinality()-originalRequestCount)) } newPeakRequests := maxRequests(current.Requests.GetCardinality() - originalRequestCount) // log.Printf( // "requests %v->%v (peak %v->%v) reason %q (peer %v)", // originalRequestCount, current.Requests.GetCardinality(), p.peakRequests, newPeakRequests, p.needRequestUpdate, p) p.peakRequests = newPeakRequests p.needRequestUpdate = "" p.lastRequestUpdate = time.Now() p.updateRequestsTimer.Reset(updateRequestsTimerDuration) } // This could be set to 10s to match the unchoke/request update interval recommended by some // specifications. I've set it shorter to trigger it more often for testing for now. const updateRequestsTimerDuration = 3 * time.Second