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Diffstat (limited to 'vendor/github.com/syndtr/goleveldb/leveldb/util/buffer_pool.go')
| -rw-r--r-- | vendor/github.com/syndtr/goleveldb/leveldb/util/buffer_pool.go | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/util/buffer_pool.go b/vendor/github.com/syndtr/goleveldb/leveldb/util/buffer_pool.go new file mode 100644 index 0000000..2f3db97 --- /dev/null +++ b/vendor/github.com/syndtr/goleveldb/leveldb/util/buffer_pool.go @@ -0,0 +1,239 @@ +// Copyright (c) 2014, Suryandaru Triandana <syndtr@gmail.com> +// All rights reserved. +// +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. + +package util + +import ( + "fmt" + "sync" + "sync/atomic" + "time" +) + +type buffer struct { + b []byte + miss int +} + +// BufferPool is a 'buffer pool'. +type BufferPool struct { + pool [6]chan []byte + size [5]uint32 + sizeMiss [5]uint32 + sizeHalf [5]uint32 + baseline [4]int + baseline0 int + + mu sync.RWMutex + closed bool + closeC chan struct{} + + get uint32 + put uint32 + half uint32 + less uint32 + equal uint32 + greater uint32 + miss uint32 +} + +func (p *BufferPool) poolNum(n int) int { + if n <= p.baseline0 && n > p.baseline0/2 { + return 0 + } + for i, x := range p.baseline { + if n <= x { + return i + 1 + } + } + return len(p.baseline) + 1 +} + +// Get returns buffer with length of n. +func (p *BufferPool) Get(n int) []byte { + if p == nil { + return make([]byte, n) + } + + p.mu.RLock() + defer p.mu.RUnlock() + + if p.closed { + return make([]byte, n) + } + + atomic.AddUint32(&p.get, 1) + + poolNum := p.poolNum(n) + pool := p.pool[poolNum] + if poolNum == 0 { + // Fast path. + select { + case b := <-pool: + switch { + case cap(b) > n: + if cap(b)-n >= n { + atomic.AddUint32(&p.half, 1) + select { + case pool <- b: + default: + } + return make([]byte, n) + } else { + atomic.AddUint32(&p.less, 1) + return b[:n] + } + case cap(b) == n: + atomic.AddUint32(&p.equal, 1) + return b[:n] + default: + atomic.AddUint32(&p.greater, 1) + } + default: + atomic.AddUint32(&p.miss, 1) + } + + return make([]byte, n, p.baseline0) + } else { + sizePtr := &p.size[poolNum-1] + + select { + case b := <-pool: + switch { + case cap(b) > n: + if cap(b)-n >= n { + atomic.AddUint32(&p.half, 1) + sizeHalfPtr := &p.sizeHalf[poolNum-1] + if atomic.AddUint32(sizeHalfPtr, 1) == 20 { + atomic.StoreUint32(sizePtr, uint32(cap(b)/2)) + atomic.StoreUint32(sizeHalfPtr, 0) + } else { + select { + case pool <- b: + default: + } + } + return make([]byte, n) + } else { + atomic.AddUint32(&p.less, 1) + return b[:n] + } + case cap(b) == n: + atomic.AddUint32(&p.equal, 1) + return b[:n] + default: + atomic.AddUint32(&p.greater, 1) + if uint32(cap(b)) >= atomic.LoadUint32(sizePtr) { + select { + case pool <- b: + default: + } + } + } + default: + atomic.AddUint32(&p.miss, 1) + } + + if size := atomic.LoadUint32(sizePtr); uint32(n) > size { + if size == 0 { + atomic.CompareAndSwapUint32(sizePtr, 0, uint32(n)) + } else { + sizeMissPtr := &p.sizeMiss[poolNum-1] + if atomic.AddUint32(sizeMissPtr, 1) == 20 { + atomic.StoreUint32(sizePtr, uint32(n)) + atomic.StoreUint32(sizeMissPtr, 0) + } + } + return make([]byte, n) + } else { + return make([]byte, n, size) + } + } +} + +// Put adds given buffer to the pool. +func (p *BufferPool) Put(b []byte) { + if p == nil { + return + } + + p.mu.RLock() + defer p.mu.RUnlock() + + if p.closed { + return + } + + atomic.AddUint32(&p.put, 1) + + pool := p.pool[p.poolNum(cap(b))] + select { + case pool <- b: + default: + } + +} + +func (p *BufferPool) Close() { + if p == nil { + return + } + + p.mu.Lock() + if !p.closed { + p.closed = true + p.closeC <- struct{}{} + } + p.mu.Unlock() +} + +func (p *BufferPool) String() string { + if p == nil { + return "<nil>" + } + + return fmt.Sprintf("BufferPool{B·%d Z·%v Zm·%v Zh·%v G·%d P·%d H·%d <·%d =·%d >·%d M·%d}", + p.baseline0, p.size, p.sizeMiss, p.sizeHalf, p.get, p.put, p.half, p.less, p.equal, p.greater, p.miss) +} + +func (p *BufferPool) drain() { + ticker := time.NewTicker(2 * time.Second) + defer ticker.Stop() + for { + select { + case <-ticker.C: + for _, ch := range p.pool { + select { + case <-ch: + default: + } + } + case <-p.closeC: + close(p.closeC) + for _, ch := range p.pool { + close(ch) + } + return + } + } +} + +// NewBufferPool creates a new initialized 'buffer pool'. +func NewBufferPool(baseline int) *BufferPool { + if baseline <= 0 { + panic("baseline can't be <= 0") + } + p := &BufferPool{ + baseline0: baseline, + baseline: [...]int{baseline / 4, baseline / 2, baseline * 2, baseline * 4}, + closeC: make(chan struct{}, 1), + } + for i, cap := range []int{2, 2, 4, 4, 2, 1} { + p.pool[i] = make(chan []byte, cap) + } + go p.drain() + return p +} |