优化代码

internal/ttlcache/cache.go

@@ -21,12 +21,18 @@ type Cache struct {
 }
 
 func NewCache(opt ...OptionInterface) *Cache {
-	countPieces := 128
-	maxItems := 2_000_000
+	var countPieces = 128
+	var maxItems = 2_000_000
 
-	var delta = systemMemoryGB() / 8
-	if delta > 0 {
-		maxItems *= delta
+	var totalMemory = systemMemoryGB()
+	if totalMemory < 2 {
+		// 我们限制内存过小的服务能够使用的数量
+		maxItems = 1_000_000
+	} else {
+		var delta = totalMemory / 8
+		if delta > 0 {
+			maxItems *= delta
+		}
 	}
 
 	for _, option := range opt {

internal/ttlcache/cache_test.go

@@ -29,12 +29,19 @@ func TestNewCache(t *testing.T) {
 }
 
 func TestCache_Memory(t *testing.T) {
+	var stat1 = &runtime.MemStats{}
+	runtime.ReadMemStats(stat1)
+
 	cache := NewCache()
-	for i := 0; i < 20_000_000; i++ {
+	for i := 0; i < 10_000_000; i++ {
 		cache.Write("a"+strconv.Itoa(i), 1, time.Now().Unix()+3600)
 	}
 	t.Log("waiting ...")
-	time.Sleep(10 * time.Second)
+
+	var stat2 = &runtime.MemStats{}
+	runtime.ReadMemStats(stat2)
+
+	t.Log((stat2.HeapInuse-stat1.HeapInuse)/1024/1024, "MB")
 }
 
 func BenchmarkCache_Add(b *testing.B) {

internal/ttlcache/piece.go

@@ -20,8 +20,14 @@ func NewPiece(maxItems int) *Piece {
 func (this *Piece) Add(key uint64, item *Item) (ok bool) {
 	this.locker.Lock()
 	if len(this.m) >= this.maxItems {
-		this.locker.Unlock()
-		return
+		// 尝试先删除过期的
+		this.gcWithoutLocker()
+
+		// 仍然是满的就跳过
+		if len(this.m) >= this.maxItems {
+			this.locker.Unlock()
+			return
+		}
 	}
 	this.m[key] = item
 	this.locker.Unlock()
@@ -74,12 +80,7 @@ func (this *Piece) Count() (count int) {
 
 func (this *Piece) GC() {
 	this.locker.Lock()
-	timestamp := time.Now().Unix()
-	for k, item := range this.m {
-		if item.expiredAt <= timestamp {
-			delete(this.m, k)
-		}
-	}
+	this.gcWithoutLocker()
 	this.locker.Unlock()
 }
 
@@ -94,3 +95,13 @@ func (this *Piece) Destroy() {
 	this.m = nil
 	this.locker.Unlock()
 }
+
+// 不加锁的gc
+func (this *Piece) gcWithoutLocker() {
+	timestamp := time.Now().Unix()
+	for k, item := range this.m {
+		if item.expiredAt <= timestamp {
+			delete(this.m, k)
+		}
+	}
+}