Merge pull request #34 from bobotu/counter

Use segment local hit and miss counter.

cache.go

@@ -9,10 +9,8 @@ import (
 )
 
 type Cache struct {
-	locks     [256]sync.Mutex
-	segments  [256]segment
-	hitCount  int64
-	missCount int64
+	locks    [256]sync.Mutex
+	segments [256]segment
 }
 
 func hashFunc(data []byte) uint64 {
@@ -53,11 +51,6 @@ func (cache *Cache) Get(key []byte) (value []byte, err error) {
 	cache.locks[segId].Lock()
 	value, _, err = cache.segments[segId].get(key, hashVal)
 	cache.locks[segId].Unlock()
-	if err == nil {
-		atomic.AddInt64(&cache.hitCount, 1)
-	} else {
-		atomic.AddInt64(&cache.missCount, 1)
-	}
 	return
 }
 
@@ -68,11 +61,6 @@ func (cache *Cache) GetWithExpiration(key []byte) (value []byte, expireAt uint32
 	cache.locks[segId].Lock()
 	value, expireAt, err = cache.segments[segId].get(key, hashVal)
 	cache.locks[segId].Unlock()
-	if err == nil {
-		atomic.AddInt64(&cache.hitCount, 1)
-	} else {
-		atomic.AddInt64(&cache.missCount, 1)
-	}
 	return
 }
 
@@ -153,20 +141,31 @@ func (cache *Cache) AverageAccessTime() int64 {
 	}
 }
 
-func (cache *Cache) HitCount() int64 {
-	return atomic.LoadInt64(&cache.hitCount)
+func (cache *Cache) HitCount() (count int64) {
+	for i := range cache.segments {
+		count += atomic.LoadInt64(&cache.segments[i].hitCount)
+	}
+	return
+}
+
+func (cache *Cache) MissCount() (count int64) {
+	for i := range cache.segments {
+		count += atomic.LoadInt64(&cache.segments[i].missCount)
+	}
+	return
 }
 
 func (cache *Cache) LookupCount() int64 {
-	return atomic.LoadInt64(&cache.hitCount) + atomic.LoadInt64(&cache.missCount)
+	return cache.HitCount() + cache.MissCount()
 }
 
 func (cache *Cache) HitRate() float64 {
-	lookupCount := cache.LookupCount()
+	hitCount, missCount := cache.HitCount(), cache.MissCount()
+	lookupCount := hitCount + missCount
 	if lookupCount == 0 {
 		return 0
 	} else {
-		return float64(cache.HitCount()) / float64(lookupCount)
+		return float64(hitCount) / float64(lookupCount)
 	}
 }
 
@@ -184,13 +183,9 @@ func (cache *Cache) Clear() {
 		cache.segments[i] = newSeg
 		cache.locks[i].Unlock()
 	}
-	atomic.StoreInt64(&cache.hitCount, 0)
-	atomic.StoreInt64(&cache.missCount, 0)
 }
 
 func (cache *Cache) ResetStatistics() {
-	atomic.StoreInt64(&cache.hitCount, 0)
-	atomic.StoreInt64(&cache.missCount, 0)
 	for i := 0; i < 256; i++ {
 		cache.locks[i].Lock()
 		cache.segments[i].resetStatistics()

segment.go

@@ -39,6 +39,8 @@ type entryHdr struct {
 type segment struct {
 	rb            RingBuf // ring buffer that stores data
 	segId         int
+	hitCount      int64
+	missCount     int64
 	entryCount    int64
 	totalCount    int64      // number of entries in ring buffer, including deleted entries.
 	totalTime     int64      // used to calculate least recent used entry.
@@ -194,6 +196,7 @@ func (seg *segment) get(key []byte, hashVal uint64) (value []byte, expireAt uint
 	idx, match := seg.lookup(slot, hash16, key)
 	if !match {
 		err = ErrNotFound
+		seg.missCount += 1
 		return
 	}
 	ptr := &slot[idx]
@@ -208,6 +211,7 @@ func (seg *segment) get(key []byte, hashVal uint64) (value []byte, expireAt uint
 		seg.delEntryPtr(slotId, hash16, ptr.offset)
 		seg.totalExpired++
 		err = ErrNotFound
+		seg.missCount += 1
 		return
 	}
 
@@ -217,6 +221,7 @@ func (seg *segment) get(key []byte, hashVal uint64) (value []byte, expireAt uint
 	value = make([]byte, hdr.valLen)
 
 	seg.rb.ReadAt(value, ptr.offset+ENTRY_HDR_SIZE+int64(hdr.keyLen))
+	seg.hitCount += 1
 	return
 }
 
@@ -365,4 +370,6 @@ func (seg *segment) resetStatistics() {
 	seg.totalEvacuate = 0
 	seg.totalExpired = 0
 	seg.overwrites = 0
+	seg.hitCount = 0
+	seg.missCount = 0
 }