accurate hit/miss counter (#44)

* accurate hit/miss counter

* update miss counter on expire

internal/store.go

@@ -19,7 +19,6 @@ import (
 )
 
 const (
-	MAX_READ_BUFF_SIZE  = 64
 	MIN_WRITE_BUFF_SIZE = 4
 	MAX_WRITE_BUFF_SIZE = 1024
 )
@@ -225,10 +224,13 @@ func (s *Store[K, V]) getFromShard(key K, hash uint64, shard *Shard[K, V]) (V, b
 		expire := entry.expire.Load()
 		if expire != 0 && expire <= s.timerwheel.clock.NowNano() {
 			ok = false
+			s.policy.miss.Add(1)
 		} else {
 			s.policy.hit.Add(1)
 			value = entry.value
 		}
+	} else {
+		s.policy.miss.Add(1)
 	}
 	shard.mu.RUnlock(tk)
 
@@ -542,7 +544,6 @@ func (s *Store[K, V]) removeEntry(entry *Entry[K, V], reason RemoveReason) {
 }
 
 func (s *Store[K, V]) drainRead(buffer []ReadBufItem[K, V]) {
-	s.policy.total.Add(MAX_READ_BUFF_SIZE)
 	s.mlock.Lock()
 	for _, e := range buffer {
 		s.policy.Access(e)

internal/store_test.go

@@ -114,3 +114,21 @@ func TestDoorKeeperDynamicSize(t *testing.T) {
 	}
 	require.True(t, shard.dookeeper.Capacity > 100000)
 }
+
+func TestPolicyCounter(t *testing.T) {
+	store := NewStore[int, int](1000, false, nil, nil, nil, 0, 0, nil)
+	for i := 0; i < 1000; i++ {
+		store.Set(i, i, 1, 0)
+	}
+	// hit
+	for i := 0; i < 1600; i++ {
+		store.Get(100)
+	}
+	// miss
+	for i := 0; i < 1600; i++ {
+		store.Get(10000)
+	}
+
+	require.Equal(t, int64(1600), store.policy.hit.Value())
+	require.Equal(t, int64(1600), store.policy.miss.Value())
+}

internal/tlfu.go

@@ -10,7 +10,7 @@ type TinyLfu[K comparable, V any] struct {
 	hasher    *Hasher[K]
 	size      uint
 	counter   uint
-	total     *Counter
+	miss      *Counter
 	hit       *Counter
 	hr        float32
 	threshold atomic.Int32
@@ -25,7 +25,7 @@ func NewTinyLfu[K comparable, V any](size uint, hasher *Hasher[K]) *TinyLfu[K, V
 		sketch: NewCountMinSketch(),
 		step:   1,
 		hasher: hasher,
-		total:  NewCounter(),
+		miss:   NewCounter(),
 		hit:    NewCounter(),
 	}
 	// default threshold to -1 so all entries are admitted until cache is full
@@ -34,9 +34,9 @@ func NewTinyLfu[K comparable, V any](size uint, hasher *Hasher[K]) *TinyLfu[K, V
 }
 
 func (t *TinyLfu[K, V]) climb() {
-	total := t.total.Value()
+	miss := t.miss.Value()
 	hit := t.hit.Value()
-	current := float32(hit) / float32(total)
+	current := float32(hit) / float32(hit+miss)
 	delta := current - t.hr
 	var diff int8
 	if delta > 0.0 {
@@ -77,7 +77,7 @@ func (t *TinyLfu[K, V]) climb() {
 	t.threshold.Add(-int32(diff))
 	t.hr = current
 	t.hit.Reset()
-	t.total.Reset()
+	t.miss.Reset()
 }
 
 func (t *TinyLfu[K, V]) Set(entry *Entry[K, V]) *Entry[K, V] {