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Merge pull request #8050 from fgrzadkowski/cache
Add cache with multiple shards to decrease lock contention
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,80 @@ | ||
| /* | ||
| Copyright 2014 The Kubernetes Authors All rights reserved. | ||
| Licensed under the Apache License, Version 2.0 (the "License"); | ||
| you may not use this file except in compliance with the License. | ||
| You may obtain a copy of the License at | ||
| http://www.apache.org/licenses/LICENSE-2.0 | ||
| Unless required by applicable law or agreed to in writing, software | ||
| distributed under the License is distributed on an "AS IS" BASIS, | ||
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| See the License for the specific language governing permissions and | ||
| limitations under the License. | ||
| */ | ||
|
|
||
| package util | ||
|
|
||
| import ( | ||
| "sync" | ||
| ) | ||
|
|
||
| const ( | ||
| shardsCount int = 32 | ||
| ) | ||
|
|
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| type Cache []*cacheShard | ||
|
|
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| func NewCache(maxSize int) Cache { | ||
| cache := make(Cache, shardsCount) | ||
| for i := 0; i < shardsCount; i++ { | ||
| cache[i] = &cacheShard{ | ||
| items: make(map[uint64]interface{}), | ||
| maxSize: maxSize / shardsCount, | ||
| } | ||
| } | ||
| return cache | ||
| } | ||
|
|
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| func (c Cache) getShard(index uint64) *cacheShard { | ||
| return c[index%uint64(shardsCount)] | ||
| } | ||
|
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| // Returns true if object already existed, false otherwise. | ||
| func (c *Cache) Add(index uint64, obj interface{}) bool { | ||
| return c.getShard(index).add(index, obj) | ||
| } | ||
|
|
||
| func (c *Cache) Get(index uint64) (obj interface{}, found bool) { | ||
| return c.getShard(index).get(index) | ||
| } | ||
|
|
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| type cacheShard struct { | ||
| items map[uint64]interface{} | ||
| sync.RWMutex | ||
| maxSize int | ||
| } | ||
|
|
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| // Returns true if object already existed, false otherwise. | ||
| func (s *cacheShard) add(index uint64, obj interface{}) bool { | ||
| s.Lock() | ||
| defer s.Unlock() | ||
| _, isOverwrite := s.items[index] | ||
| s.items[index] = obj | ||
| if len(s.items) > s.maxSize { | ||
| var randomKey uint64 | ||
| for randomKey = range s.items { | ||
| break | ||
| } | ||
| delete(s.items, randomKey) | ||
| } | ||
| return isOverwrite | ||
| } | ||
|
|
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| func (s *cacheShard) get(index uint64) (obj interface{}, found bool) { | ||
| s.RLock() | ||
| defer s.RUnlock() | ||
| obj, found = s.items[index] | ||
| return | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,65 @@ | ||
| /* | ||
| Copyright 2014 The Kubernetes Authors All rights reserved. | ||
| Licensed under the Apache License, Version 2.0 (the "License"); | ||
| you may not use this file except in compliance with the License. | ||
| You may obtain a copy of the License at | ||
| http://www.apache.org/licenses/LICENSE-2.0 | ||
| Unless required by applicable law or agreed to in writing, software | ||
| distributed under the License is distributed on an "AS IS" BASIS, | ||
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| See the License for the specific language governing permissions and | ||
| limitations under the License. | ||
| */ | ||
|
|
||
| package util | ||
|
|
||
| import ( | ||
| "testing" | ||
| ) | ||
|
|
||
| const ( | ||
| maxTestCacheSize int = shardsCount * 2 | ||
| ) | ||
|
|
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| func ExpectEntry(t *testing.T, cache Cache, index uint64, expectedValue interface{}) { | ||
| elem, found := cache.Get(index) | ||
| if !found { | ||
| t.Error("Expected to find entry with key 1") | ||
| } else if elem != expectedValue { | ||
| t.Errorf("Expected to find %v, got %v", expectedValue, elem) | ||
| } | ||
| } | ||
|
|
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| func TestBasic(t *testing.T) { | ||
| cache := NewCache(maxTestCacheSize) | ||
| cache.Add(1, "xxx") | ||
| ExpectEntry(t, cache, 1, "xxx") | ||
| } | ||
|
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| func TestOverflow(t *testing.T) { | ||
| cache := NewCache(maxTestCacheSize) | ||
| for i := 0; i < maxTestCacheSize+1; i++ { | ||
| cache.Add(uint64(i), "xxx") | ||
| } | ||
| foundIndexes := make([]uint64, 0) | ||
| for i := 0; i < maxTestCacheSize+1; i++ { | ||
| _, found := cache.Get(uint64(i)) | ||
| if found { | ||
| foundIndexes = append(foundIndexes, uint64(i)) | ||
| } | ||
| } | ||
| if len(foundIndexes) != maxTestCacheSize { | ||
| t.Errorf("Expect to find %d elements, got %d %v", maxTestCacheSize, len(foundIndexes), foundIndexes) | ||
| } | ||
| } | ||
|
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| func TestOverwrite(t *testing.T) { | ||
| cache := NewCache(maxTestCacheSize) | ||
| cache.Add(1, "xxx") | ||
| ExpectEntry(t, cache, 1, "xxx") | ||
| cache.Add(1, "yyy") | ||
| ExpectEntry(t, cache, 1, "yyy") | ||
| } |