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Improve cache locality by removing Item-related pointers

This commit is contained in:
Patrick Mylund Nielsen 2015-11-28 14:47:46 -05:00
parent 3d4d09ca0b
commit 901b2413ee
3 changed files with 55 additions and 24 deletions
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63
cache.go
View File

@ -10,14 +10,16 @@ import (
"time"
)
var emptyTime = time.Time{}
type Item struct {
Object interface{}
Expiration *time.Time
Expiration time.Time
}
// Returns true if the item has expired.
func (item *Item) Expired() bool {
if item.Expiration == nil {
func (item Item) Expired() bool {
if item.Expiration == emptyTime {
return false
}
return item.Expiration.Before(time.Now())
@ -39,7 +41,7 @@ type Cache struct {
type cache struct {
defaultExpiration time.Duration
items map[string]*Item
items map[string]Item
mu sync.RWMutex
onEvicted func(string, interface{})
janitor *janitor
@ -57,15 +59,14 @@ func (c *cache) Set(k string, x interface{}, d time.Duration) {
}
func (c *cache) set(k string, x interface{}, d time.Duration) {
var e *time.Time
e := emptyTime
if d == DefaultExpiration {
d = c.defaultExpiration
}
if d > 0 {
t := time.Now().Add(d)
e = &t
e = time.Now().Add(d)
}
c.items[k] = &Item{
c.items[k] = Item{
Object: x,
Expiration: e,
}
@ -159,6 +160,7 @@ func (c *cache) Increment(k string, n int64) error {
c.mu.Unlock()
return fmt.Errorf("The value for %s is not an integer", k)
}
c.items[k] = v
c.mu.Unlock()
return nil
}
@ -184,6 +186,7 @@ func (c *cache) IncrementFloat(k string, n float64) error {
c.mu.Unlock()
return fmt.Errorf("The value for %s does not have type float32 or float64", k)
}
c.items[k] = v
c.mu.Unlock()
return nil
}
@ -205,6 +208,7 @@ func (c *cache) IncrementInt(k string, n int) (int, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -226,6 +230,7 @@ func (c *cache) IncrementInt8(k string, n int8) (int8, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -247,6 +252,7 @@ func (c *cache) IncrementInt16(k string, n int16) (int16, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -268,6 +274,7 @@ func (c *cache) IncrementInt32(k string, n int32) (int32, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -289,6 +296,7 @@ func (c *cache) IncrementInt64(k string, n int64) (int64, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -310,6 +318,7 @@ func (c *cache) IncrementUint(k string, n uint) (uint, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -331,6 +340,7 @@ func (c *cache) IncrementUintptr(k string, n uintptr) (uintptr, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -352,6 +362,7 @@ func (c *cache) IncrementUint8(k string, n uint8) (uint8, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -373,6 +384,7 @@ func (c *cache) IncrementUint16(k string, n uint16) (uint16, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -394,6 +406,7 @@ func (c *cache) IncrementUint32(k string, n uint32) (uint32, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -415,6 +428,7 @@ func (c *cache) IncrementUint64(k string, n uint64) (uint64, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -436,6 +450,7 @@ func (c *cache) IncrementFloat32(k string, n float32) (float32, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -457,6 +472,7 @@ func (c *cache) IncrementFloat64(k string, n float64) (float64, error) {
}
nv := rv + n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -506,6 +522,7 @@ func (c *cache) Decrement(k string, n int64) error {
c.mu.Unlock()
return fmt.Errorf("The value for %s is not an integer", k)
}
c.items[k] = v
c.mu.Unlock()
return nil
}
@ -531,6 +548,7 @@ func (c *cache) DecrementFloat(k string, n float64) error {
c.mu.Unlock()
return fmt.Errorf("The value for %s does not have type float32 or float64", k)
}
c.items[k] = v
c.mu.Unlock()
return nil
}
@ -552,6 +570,7 @@ func (c *cache) DecrementInt(k string, n int) (int, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -573,6 +592,7 @@ func (c *cache) DecrementInt8(k string, n int8) (int8, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -594,6 +614,7 @@ func (c *cache) DecrementInt16(k string, n int16) (int16, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -615,6 +636,7 @@ func (c *cache) DecrementInt32(k string, n int32) (int32, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -636,6 +658,7 @@ func (c *cache) DecrementInt64(k string, n int64) (int64, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -657,6 +680,7 @@ func (c *cache) DecrementUint(k string, n uint) (uint, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -678,6 +702,7 @@ func (c *cache) DecrementUintptr(k string, n uintptr) (uintptr, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -699,6 +724,7 @@ func (c *cache) DecrementUint8(k string, n uint8) (uint8, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -720,6 +746,7 @@ func (c *cache) DecrementUint16(k string, n uint16) (uint16, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -741,6 +768,7 @@ func (c *cache) DecrementUint32(k string, n uint32) (uint32, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -762,6 +790,7 @@ func (c *cache) DecrementUint64(k string, n uint64) (uint64, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -783,6 +812,7 @@ func (c *cache) DecrementFloat32(k string, n float32) (float32, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -804,6 +834,7 @@ func (c *cache) DecrementFloat64(k string, n float64) (float64, error) {
}
nv := rv - n
v.Object = nv
c.items[k] = v
c.mu.Unlock()
return nv, nil
}
@ -906,7 +937,7 @@ func (c *cache) SaveFile(fname string) error {
// documentation for NewFrom().)
func (c *cache) Load(r io.Reader) error {
dec := gob.NewDecoder(r)
items := map[string]*Item{}
items := map[string]Item{}
err := dec.Decode(&items)
if err == nil {
c.mu.Lock()
@ -944,7 +975,7 @@ func (c *cache) LoadFile(fname string) error {
// fields of the items should be checked. Note that explicit synchronization
// is needed to use a cache and its corresponding Items() return value at
// the same time, as the map is shared.
func (c *cache) Items() map[string]*Item {
func (c *cache) Items() map[string]Item {
c.mu.RLock()
defer c.mu.RUnlock()
return c.items
@ -962,7 +993,7 @@ func (c *cache) ItemCount() int {
// Delete all items from the cache.
func (c *cache) Flush() {
c.mu.Lock()
c.items = map[string]*Item{}
c.items = map[string]Item{}
c.mu.Unlock()
}
@ -997,7 +1028,7 @@ func runJanitor(c *cache, ci time.Duration) {
go j.Run(c)
}
func newCache(de time.Duration, m map[string]*Item) *cache {
func newCache(de time.Duration, m map[string]Item) *cache {
if de == 0 {
de = -1
}
@ -1008,7 +1039,7 @@ func newCache(de time.Duration, m map[string]*Item) *cache {
return c
}
func newCacheWithJanitor(de time.Duration, ci time.Duration, m map[string]*Item) *Cache {
func newCacheWithJanitor(de time.Duration, ci time.Duration, m map[string]Item) *Cache {
c := newCache(de, m)
// This trick ensures that the janitor goroutine (which--granted it
// was enabled--is running DeleteExpired on c forever) does not keep
@ -1029,7 +1060,7 @@ func newCacheWithJanitor(de time.Duration, ci time.Duration, m map[string]*Item)
// manually. If the cleanup interval is less than one, expired items are not
// deleted from the cache before calling c.DeleteExpired().
func New(defaultExpiration, cleanupInterval time.Duration) *Cache {
items := make(map[string]*Item)
items := make(map[string]Item)
return newCacheWithJanitor(defaultExpiration, cleanupInterval, items)
}
@ -1042,7 +1073,7 @@ func New(defaultExpiration, cleanupInterval time.Duration) *Cache {
// NewFrom() also accepts an items map which will serve as the underlying map
// for the cache. This is useful for starting from a deserialized cache
// (serialized using e.g. gob.Encode() on c.Items()), or passing in e.g.
// make(map[string]*Item, 500) to improve startup performance when the cache
// make(map[string]Item, 500) to improve startup performance when the cache
// is expected to reach a certain minimum size.
//
// Only the cache's methods synchronize access to this map, so it is not
@ -1054,6 +1085,6 @@ func New(defaultExpiration, cleanupInterval time.Duration) *Cache {
// gob.Register() the individual types stored in the cache before encoding a
// map retrieved with c.Items(), and to register those same types before
// decoding a blob containing an items map.
func NewFrom(defaultExpiration, cleanupInterval time.Duration, items map[string]*Item) *Cache {
func NewFrom(defaultExpiration, cleanupInterval time.Duration, items map[string]Item) *Cache {
return newCacheWithJanitor(defaultExpiration, cleanupInterval, items)
}

10
cache_test.go
View File

@ -107,14 +107,14 @@ func TestCacheTimes(t *testing.T) {
}
func TestNewFrom(t *testing.T) {
m := map[string]*Item{
"a": &Item{
m := map[string]Item{
"a": Item{
Object: 1,
Expiration: nil,
Expiration: emptyTime,
},
"b": &Item{
"b": Item{
Object: 2,
Expiration: nil,
Expiration: emptyTime,
},
}
tc := NewFrom(DefaultExpiration, 0, m)

6
sharded.go
View File

@ -109,8 +109,8 @@ func (sc *shardedCache) DeleteExpired() {
// fields of the items should be checked. Note that explicit synchronization
// is needed to use a cache and its corresponding Items() return values at
// the same time, as the maps are shared.
func (sc *shardedCache) Items() []map[string]*Item {
res := make([]map[string]*Item, len(sc.cs))
func (sc *shardedCache) Items() []map[string]Item {
res := make([]map[string]Item, len(sc.cs))
for i, v := range sc.cs {
res[i] = v.Items()
}
@ -171,7 +171,7 @@ func newShardedCache(n int, de time.Duration) *shardedCache {
for i := 0; i < n; i++ {
c := &cache{
defaultExpiration: de,
items: map[string]*Item{},
items: map[string]Item{},
}
sc.cs[i] = c
}