perf: Speedup cachekv iterator on large deletions & IBC v2 upgrade lo…

…gic (backport cosmos#10741) (cosmos#10744)

* perf: Speedup cachekv iterator on large deletions & IBC v2 upgrade logic (cosmos#10741)

(cherry picked from commit 314e1d5)

# Conflicts:
#	CHANGELOG.md
#	store/cachekv/store_bench_test.go

* fix conflicts

* add helpers

Co-authored-by: Dev Ojha <ValarDragon@users.noreply.github.com>
Co-authored-by: marbar3778 <marbar3778@yahoo.com>

CHANGELOG.md

@@ -45,6 +45,10 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (store) [#10218](https://github.com/cosmos/cosmos-sdk/pull/10218) Charge gas even when there are no entries while seeking.
 * (store) [#10247](https://github.com/cosmos/cosmos-sdk/pull/10247) Charge gas for the key length in gas meter.
 
+### Improvements
+
+* (store) [\#10741](https://github.com/cosmos/cosmos-sdk/pull/10741) Significantly speedup iterator creation after delete heavy workloads. Significantly improves IBC migration times.
+
 ## [v0.44.5](https://github.com/cosmos/cosmos-sdk/releases/tag/v0.44.5) - 2021-12-02
 
 ### Improvements

store/cachekv/bench_helper_test.go

@@ -34,7 +34,7 @@ func generateSequentialKeys(startKey []byte, numKeys int) [][]byte {
 }
 
 // Generate many random, unsorted keys
-func generateRandomKeys(keySize, numKeys int) [][]byte {
+func generateRandomKeys(keySize int, numKeys int) [][]byte {
 	toReturn := make([][]byte, 0, numKeys)
 	for i := 0; i < numKeys; i++ {
 		newKey := randSlice(keySize)

store/cachekv/store_bench_test.go

@@ -14,8 +14,7 @@ const defaultValueSizeBz = 1 << 12
 
 // This benchmark measures the time of iterator.Next() when the parent store is blank
 func benchmarkBlankParentIteratorNext(b *testing.B, keysize int) {
-	b.Helper()
-	mem := dbadapter.Store{DB: coretesting.NewMemDB()}
+	mem := dbadapter.Store{DB: dbm.NewMemDB()}
 	kvstore := cachekv.NewStore(mem)
 	// Use a singleton for value, to not waste time computing it
 	value := randSlice(defaultValueSizeBz)
@@ -35,17 +34,15 @@ func benchmarkBlankParentIteratorNext(b *testing.B, keysize int) {
 	iter := kvstore.Iterator(keys[0], keys[b.N])
 	defer iter.Close()
 
-	for ; iter.Valid(); iter.Next() {
-		_ = iter.Key()
+	for _ = iter.Key(); iter.Valid(); iter.Next() {
 		// deadcode elimination stub
 		sink = iter
 	}
 }
 
 // Benchmark setting New keys to a store, where the new keys are in sequence.
 func benchmarkBlankParentAppend(b *testing.B, keysize int) {
-	b.Helper()
-	mem := dbadapter.Store{DB: coretesting.NewMemDB()}
+	mem := dbadapter.Store{DB: dbm.NewMemDB()}
 	kvstore := cachekv.NewStore(mem)
 
 	// Use a singleton for value, to not waste time computing it
@@ -67,14 +64,12 @@ func benchmarkBlankParentAppend(b *testing.B, keysize int) {
 // Benchmark setting New keys to a store, where the new keys are random.
 // the speed of this function does not depend on the values in the parent store
 func benchmarkRandomSet(b *testing.B, keysize int) {
-	b.Helper()
-	mem := dbadapter.Store{DB: coretesting.NewMemDB()}
+	mem := dbadapter.Store{DB: dbm.NewMemDB()}
 	kvstore := cachekv.NewStore(mem)
 
 	// Use a singleton for value, to not waste time computing it
 	value := randSlice(defaultValueSizeBz)
-	// Add 1 to avoid issues when b.N = 1
-	keys := generateRandomKeys(keysize, b.N+1)
+	keys := generateRandomKeys(keysize, b.N)
 
 	b.ReportAllocs()
 	b.ResetTimer()
@@ -86,8 +81,7 @@ func benchmarkRandomSet(b *testing.B, keysize int) {
 	iter := kvstore.Iterator(keys[0], keys[b.N])
 	defer iter.Close()
 
-	for ; iter.Valid(); iter.Next() {
-		_ = iter.Key()
+	for _ = iter.Key(); iter.Valid(); iter.Next() {
 		// deadcode elimination stub
 		sink = iter
 	}
@@ -98,16 +92,14 @@ func benchmarkRandomSet(b *testing.B, keysize int) {
 // We essentially are benchmarking the cacheKV iterator creation & iteration times
 // with the number of entries deleted in the parent.
 func benchmarkIteratorOnParentWithManyDeletes(b *testing.B, numDeletes int) {
-	b.Helper()
-	mem := dbadapter.Store{DB: coretesting.NewMemDB()}
+	mem := dbadapter.Store{DB: dbm.NewMemDB()}
 
 	// Use a singleton for value, to not waste time computing it
 	value := randSlice(32)
 	// Use simple values for keys, pick a random start,
 	// and take next D keys sequentially after.
 	startKey := randSlice(32)
-	// Add 1 to avoid issues when numDeletes = 1
-	keys := generateSequentialKeys(startKey, numDeletes+1)
+	keys := generateSequentialKeys(startKey, numDeletes)
 	// setup parent db with D keys.
 	for _, k := range keys {
 		mem.Set(k, value)
@@ -125,11 +117,10 @@ func benchmarkIteratorOnParentWithManyDeletes(b *testing.B, numDeletes int) {
 	b.ReportAllocs()
 	b.ResetTimer()
 
-	iter := kvstore.Iterator(keys[0], keys[numDeletes])
+	iter := kvstore.Iterator(keys[0], keys[b.N])
 	defer iter.Close()
 
-	for ; iter.Valid(); iter.Next() {
-		_ = iter.Key()
+	for _ = iter.Key(); iter.Valid(); iter.Next() {
 		// deadcode elimination stub
 		sink = iter
 	}