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fd_operator_cache.go
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fd_operator_cache.go
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// Copyright 2022 CloudWeGo Authors
//
// 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 netpoll
import (
"runtime"
"sync/atomic"
"unsafe"
)
func newOperatorCache() *operatorCache {
return &operatorCache{
cache: make([]*FDOperator, 0, 1024),
freelist: make([]int32, 0, 1024),
}
}
type operatorCache struct {
locked int32
first *FDOperator
cache []*FDOperator
// freelist store the freeable operator
// to reduce GC pressure, we only store op index here
freelist []int32
freelocked int32
}
func (c *operatorCache) alloc() *FDOperator {
lock(&c.locked)
if c.first == nil {
const opSize = unsafe.Sizeof(FDOperator{})
n := block4k / opSize
if n == 0 {
n = 1
}
index := int32(len(c.cache))
for i := uintptr(0); i < n; i++ {
pd := &FDOperator{index: index}
c.cache = append(c.cache, pd)
pd.next = c.first
c.first = pd
index++
}
}
op := c.first
c.first = op.next
unlock(&c.locked)
return op
}
// freeable mark the operator that could be freed
// only poller could do the real free action
func (c *operatorCache) freeable(op *FDOperator) {
// reset all state
op.unused()
op.reset()
lock(&c.freelocked)
c.freelist = append(c.freelist, op.index)
unlock(&c.freelocked)
}
func (c *operatorCache) free() {
lock(&c.freelocked)
defer unlock(&c.freelocked)
if len(c.freelist) == 0 {
return
}
lock(&c.locked)
for _, idx := range c.freelist {
op := c.cache[idx]
op.next = c.first
c.first = op
}
c.freelist = c.freelist[:0]
unlock(&c.locked)
}
func lock(locked *int32) {
for !atomic.CompareAndSwapInt32(locked, 0, 1) {
runtime.Gosched()
}
}
func unlock(locked *int32) {
atomic.StoreInt32(locked, 0)
}