X-Git-Url: http://git.osdn.net/view?p=bytom%2Fvapor.git;a=blobdiff_plain;f=vendor%2Fgithub.com%2Fhashicorp%2Fgolang-lru%2Farc.go;fp=vendor%2Fgithub.com%2Fhashicorp%2Fgolang-lru%2Farc.go;h=0000000000000000000000000000000000000000;hp=555225a218c968e756812976829e3d548e7bffda;hb=54373c1a3efe0e373ec1605840a4363e4b246c46;hpb=ee01d543fdfe1fd0a4d548965c66f7923ea7b062 diff --git a/vendor/github.com/hashicorp/golang-lru/arc.go b/vendor/github.com/hashicorp/golang-lru/arc.go deleted file mode 100644 index 555225a2..00000000 --- a/vendor/github.com/hashicorp/golang-lru/arc.go +++ /dev/null @@ -1,257 +0,0 @@ -package lru - -import ( - "sync" - - "github.com/hashicorp/golang-lru/simplelru" -) - -// ARCCache is a thread-safe fixed size Adaptive Replacement Cache (ARC). -// ARC is an enhancement over the standard LRU cache in that tracks both -// frequency and recency of use. This avoids a burst in access to new -// entries from evicting the frequently used older entries. It adds some -// additional tracking overhead to a standard LRU cache, computationally -// it is roughly 2x the cost, and the extra memory overhead is linear -// with the size of the cache. ARC has been patented by IBM, but is -// similar to the TwoQueueCache (2Q) which requires setting parameters. -type ARCCache struct { - size int // Size is the total capacity of the cache - p int // P is the dynamic preference towards T1 or T2 - - t1 simplelru.LRUCache // T1 is the LRU for recently accessed items - b1 simplelru.LRUCache // B1 is the LRU for evictions from t1 - - t2 simplelru.LRUCache // T2 is the LRU for frequently accessed items - b2 simplelru.LRUCache // B2 is the LRU for evictions from t2 - - lock sync.RWMutex -} - -// NewARC creates an ARC of the given size -func NewARC(size int) (*ARCCache, error) { - // Create the sub LRUs - b1, err := simplelru.NewLRU(size, nil) - if err != nil { - return nil, err - } - b2, err := simplelru.NewLRU(size, nil) - if err != nil { - return nil, err - } - t1, err := simplelru.NewLRU(size, nil) - if err != nil { - return nil, err - } - t2, err := simplelru.NewLRU(size, nil) - if err != nil { - return nil, err - } - - // Initialize the ARC - c := &ARCCache{ - size: size, - p: 0, - t1: t1, - b1: b1, - t2: t2, - b2: b2, - } - return c, nil -} - -// Get looks up a key's value from the cache. -func (c *ARCCache) Get(key interface{}) (value interface{}, ok bool) { - c.lock.Lock() - defer c.lock.Unlock() - - // If the value is contained in T1 (recent), then - // promote it to T2 (frequent) - if val, ok := c.t1.Peek(key); ok { - c.t1.Remove(key) - c.t2.Add(key, val) - return val, ok - } - - // Check if the value is contained in T2 (frequent) - if val, ok := c.t2.Get(key); ok { - return val, ok - } - - // No hit - return nil, false -} - -// Add adds a value to the cache. -func (c *ARCCache) Add(key, value interface{}) { - c.lock.Lock() - defer c.lock.Unlock() - - // Check if the value is contained in T1 (recent), and potentially - // promote it to frequent T2 - if c.t1.Contains(key) { - c.t1.Remove(key) - c.t2.Add(key, value) - return - } - - // Check if the value is already in T2 (frequent) and update it - if c.t2.Contains(key) { - c.t2.Add(key, value) - return - } - - // Check if this value was recently evicted as part of the - // recently used list - if c.b1.Contains(key) { - // T1 set is too small, increase P appropriately - delta := 1 - b1Len := c.b1.Len() - b2Len := c.b2.Len() - if b2Len > b1Len { - delta = b2Len / b1Len - } - if c.p+delta >= c.size { - c.p = c.size - } else { - c.p += delta - } - - // Potentially need to make room in the cache - if c.t1.Len()+c.t2.Len() >= c.size { - c.replace(false) - } - - // Remove from B1 - c.b1.Remove(key) - - // Add the key to the frequently used list - c.t2.Add(key, value) - return - } - - // Check if this value was recently evicted as part of the - // frequently used list - if c.b2.Contains(key) { - // T2 set is too small, decrease P appropriately - delta := 1 - b1Len := c.b1.Len() - b2Len := c.b2.Len() - if b1Len > b2Len { - delta = b1Len / b2Len - } - if delta >= c.p { - c.p = 0 - } else { - c.p -= delta - } - - // Potentially need to make room in the cache - if c.t1.Len()+c.t2.Len() >= c.size { - c.replace(true) - } - - // Remove from B2 - c.b2.Remove(key) - - // Add the key to the frequently used list - c.t2.Add(key, value) - return - } - - // Potentially need to make room in the cache - if c.t1.Len()+c.t2.Len() >= c.size { - c.replace(false) - } - - // Keep the size of the ghost buffers trim - if c.b1.Len() > c.size-c.p { - c.b1.RemoveOldest() - } - if c.b2.Len() > c.p { - c.b2.RemoveOldest() - } - - // Add to the recently seen list - c.t1.Add(key, value) - return -} - -// replace is used to adaptively evict from either T1 or T2 -// based on the current learned value of P -func (c *ARCCache) replace(b2ContainsKey bool) { - t1Len := c.t1.Len() - if t1Len > 0 && (t1Len > c.p || (t1Len == c.p && b2ContainsKey)) { - k, _, ok := c.t1.RemoveOldest() - if ok { - c.b1.Add(k, nil) - } - } else { - k, _, ok := c.t2.RemoveOldest() - if ok { - c.b2.Add(k, nil) - } - } -} - -// Len returns the number of cached entries -func (c *ARCCache) Len() int { - c.lock.RLock() - defer c.lock.RUnlock() - return c.t1.Len() + c.t2.Len() -} - -// Keys returns all the cached keys -func (c *ARCCache) Keys() []interface{} { - c.lock.RLock() - defer c.lock.RUnlock() - k1 := c.t1.Keys() - k2 := c.t2.Keys() - return append(k1, k2...) -} - -// Remove is used to purge a key from the cache -func (c *ARCCache) Remove(key interface{}) { - c.lock.Lock() - defer c.lock.Unlock() - if c.t1.Remove(key) { - return - } - if c.t2.Remove(key) { - return - } - if c.b1.Remove(key) { - return - } - if c.b2.Remove(key) { - return - } -} - -// Purge is used to clear the cache -func (c *ARCCache) Purge() { - c.lock.Lock() - defer c.lock.Unlock() - c.t1.Purge() - c.t2.Purge() - c.b1.Purge() - c.b2.Purge() -} - -// Contains is used to check if the cache contains a key -// without updating recency or frequency. -func (c *ARCCache) Contains(key interface{}) bool { - c.lock.RLock() - defer c.lock.RUnlock() - return c.t1.Contains(key) || c.t2.Contains(key) -} - -// Peek is used to inspect the cache value of a key -// without updating recency or frequency. -func (c *ARCCache) Peek(key interface{}) (value interface{}, ok bool) { - c.lock.RLock() - defer c.lock.RUnlock() - if val, ok := c.t1.Peek(key); ok { - return val, ok - } - return c.t2.Peek(key) -}