Benchmark PieceRequestOrder with varying styles of path hint usage

Add per-piece piece request order path hints

piece.go

@@ -8,7 +8,6 @@ import (
 	"github.com/RoaringBitmap/roaring"
 	"github.com/anacrolix/chansync"
 	"github.com/anacrolix/missinggo/v2/bitmap"
-
 	"github.com/anacrolix/torrent/metainfo"
 	pp "github.com/anacrolix/torrent/peer_protocol"
 	"github.com/anacrolix/torrent/storage"

request-strategy/piece-request-order.go

@@ -21,7 +21,7 @@ func NewPieceOrder() *PieceRequestOrder {
 type PieceRequestOrder struct {
 	tree     *btree.BTree[pieceRequestOrderItem]
 	keys     map[PieceRequestOrderKey]PieceRequestOrderState
-	pathHint btree.PathHint
+	PathHint *btree.PathHint
 }
 
 type PieceRequestOrderKey struct {
@@ -51,7 +51,7 @@ func (me *PieceRequestOrder) Add(key PieceRequestOrderKey, state PieceRequestOrd
 	if _, ok := me.tree.SetHint(pieceRequestOrderItem{
 		key:   key,
 		state: state,
-	}, &me.pathHint); ok {
+	}, me.PathHint); ok {
 		panic("shouldn't already have this")
 	}
 	me.keys[key] = state
@@ -59,7 +59,10 @@ func (me *PieceRequestOrder) Add(key PieceRequestOrderKey, state PieceRequestOrd
 
 type PieceRequestOrderPathHint = btree.PathHint
 
-func (me *PieceRequestOrder) Update(key PieceRequestOrderKey, state PieceRequestOrderState) {
+func (me *PieceRequestOrder) Update(
+	key PieceRequestOrderKey,
+	state PieceRequestOrderState,
+) {
 	oldState, ok := me.keys[key]
 	if !ok {
 		panic("key should have been added already")
@@ -71,11 +74,11 @@ func (me *PieceRequestOrder) Update(key PieceRequestOrderKey, state PieceRequest
 		key:   key,
 		state: oldState,
 	}
-	if _, ok := me.tree.DeleteHint(item, &me.pathHint); !ok {
+	if _, ok := me.tree.DeleteHint(item, me.PathHint); !ok {
 		panic(fmt.Sprintf("%#v", key))
 	}
 	item.state = state
-	if _, ok := me.tree.SetHint(item, &me.pathHint); ok {
+	if _, ok := me.tree.SetHint(item, me.PathHint); ok {
 		panic(key)
 	}
 	me.keys[key] = state
@@ -90,7 +93,7 @@ func (me *PieceRequestOrder) existingItemForKey(key PieceRequestOrderKey) pieceR
 
 func (me *PieceRequestOrder) Delete(key PieceRequestOrderKey) {
 	item := me.existingItemForKey(key)
-	if _, ok := me.tree.DeleteHint(item, &me.pathHint); !ok {
+	if _, ok := me.tree.DeleteHint(item, me.PathHint); !ok {
 		panic(key)
 	}
 	delete(me.keys, key)

request-strategy/piece-request-order_test.go

@@ -0,0 +1,74 @@
+package request_strategy
+
+import (
+	"testing"
+
+	"github.com/bradfitz/iter"
+)
+
+func benchmarkPieceRequestOrder(
+	b *testing.B,
+	hintForPiece func(index int) *PieceRequestOrderPathHint,
+	numPieces int,
+) {
+	b.ResetTimer()
+	b.ReportAllocs()
+	for range iter.N(b.N) {
+		pro := NewPieceOrder()
+		state := PieceRequestOrderState{}
+		doPieces := func(m func(PieceRequestOrderKey)) {
+			for i := range iter.N(numPieces) {
+				key := PieceRequestOrderKey{
+					Index: i,
+				}
+				pro.PathHint = hintForPiece(i)
+				m(key)
+			}
+		}
+		doPieces(func(key PieceRequestOrderKey) {
+			pro.Add(key, state)
+		})
+		state.Availability++
+		doPieces(func(key PieceRequestOrderKey) {
+			pro.Update(key, state)
+		})
+		doPieces(func(key PieceRequestOrderKey) {
+			state.Priority = piecePriority(key.Index / 4)
+			pro.Update(key, state)
+		})
+		// state.Priority = 0
+		state.Availability++
+		doPieces(func(key PieceRequestOrderKey) {
+			pro.Update(key, state)
+		})
+		state.Availability--
+		doPieces(func(key PieceRequestOrderKey) {
+			pro.Update(key, state)
+		})
+		doPieces(pro.Delete)
+		if pro.Len() != 0 {
+			b.FailNow()
+		}
+	}
+}
+
+func BenchmarkPieceRequestOrder(b *testing.B) {
+	const numPieces = 2000
+	b.Run("NoPathHints", func(b *testing.B) {
+		benchmarkPieceRequestOrder(b, func(int) *PieceRequestOrderPathHint {
+			return nil
+		}, numPieces)
+	})
+	b.Run("SharedPathHint", func(b *testing.B) {
+		var pathHint PieceRequestOrderPathHint
+		benchmarkPieceRequestOrder(b, func(int) *PieceRequestOrderPathHint {
+			return &pathHint
+		}, numPieces)
+	})
+	b.Run("PathHintPerPiece", func(b *testing.B) {
+		pathHints := make([]PieceRequestOrderPathHint, numPieces)
+		benchmarkPieceRequestOrder(b, func(index int) *PieceRequestOrderPathHint {
+			return &pathHints[index]
+		}, numPieces)
+	})
+}