Minimize allocations and resizing in request computation

diff --git a/request-strategy/order.go b/request-strategy/order.go
index 2a364eb85cc733caa1f9e40bf511b59dc371a70d..5a48ba456c696a5f38e69b96e229ea1d2cc55972 100644 (file)
--- a/request-strategy/order.go
+++ b/request-strategy/order.go
@@ -21,7 +21,7 @@ type (
 type ClientPieceOrder struct{}
 
 type filterTorrent struct {
-       Torrent
+       *Torrent
        unverifiedBytes int64
        // Potentially shared with other torrents.
        storageLeft *int64
@@ -29,8 +29,8 @@ type filterTorrent struct {
 
 func sortFilterPieces(pieces []filterPiece) {
        sort.Slice(pieces, func(_i, _j int) bool {
-               i := pieces[_i]
-               j := pieces[_j]
+               i := &pieces[_i]
+               j := &pieces[_j]
                return multiless.New().Int(
                        int(j.Priority), int(i.Priority),
                ).Bool(
@@ -75,7 +75,7 @@ func (me *peersForPieceRequests) addNextRequest(r Request) {
 
 type requestablePiece struct {
        index             pieceIndex
-       t                 Torrent
+       t                 *Torrent
        alwaysReallocate  bool
        NumPendingChunks  int
        IterPendingChunks ChunksIter
@@ -84,18 +84,23 @@ type requestablePiece struct {
 type filterPiece struct {
        t     *filterTorrent
        index pieceIndex
-       Piece
+       *Piece
 }
 
 func getRequestablePieces(input Input) (ret []requestablePiece) {
+       maxPieces := 0
+       for i := range input.Torrents {
+               maxPieces += len(input.Torrents[i].Pieces)
+       }
+       pieces := make([]filterPiece, 0, maxPieces)
+       ret = make([]requestablePiece, 0, maxPieces)
        // Storage capacity left for this run, keyed by the storage capacity pointer on the storage
        // TorrentImpl.
        storageLeft := make(map[*func() *int64]*int64)
-       var pieces []filterPiece
-       for _, _t := range input.Torrents {
+       for _t := range input.Torrents {
                // TODO: We could do metainfo requests here.
                t := &filterTorrent{
-                       Torrent:         _t,
+                       Torrent:         &input.Torrents[_t],
                        unverifiedBytes: 0,
                }
                key := t.Capacity
@@ -105,11 +110,11 @@ func getRequestablePieces(input Input) (ret []requestablePiece) {
                        }
                        t.storageLeft = storageLeft[key]
                }
-               for i, tp := range t.Pieces {
+               for i := range t.Pieces {
                        pieces = append(pieces, filterPiece{
                                t:     t,
                                index: i,
-                               Piece: tp,
+                               Piece: &t.Pieces[i],
                        })
                }
        }