-
Notifications
You must be signed in to change notification settings - Fork 5.7k
/
gp.go
181 lines (165 loc) · 3.85 KB
/
gp.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
// Copyright 2017 PingCAP, Inc.
//
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package gp
import (
"sync"
"time"
)
// Pool is a struct to represent goroutine pool.
type Pool struct {
head goroutine
tail *goroutine
count int
idleTimeout time.Duration
sync.Mutex
// gcWorker marks whether there is a gcWorker currently.
// only gc worker goroutine can modify it, others just read it.
gcWorker struct {
sync.RWMutex
value bool
}
}
// goroutine is actually a background goroutine, with a channel binded for communication.
type goroutine struct {
ch chan func()
lastRun time.Time
pool *Pool
next *goroutine
}
// New returns a new *Pool object.
func New(idleTimeout time.Duration) *Pool {
pool := &Pool{
idleTimeout: idleTimeout,
}
pool.tail = &pool.head
return pool
}
// Go works like go func(), but goroutines are pooled for reusing.
// This strategy can avoid runtime.morestack, because pooled goroutine is already enlarged.
func (pool *Pool) Go(f func()) {
g := pool.get()
g.ch <- f
// When the goroutine finish f(), it will be put back to pool automatically,
// so it doesn't need to call pool.put() here.
}
func (pool *Pool) get() *goroutine {
pool.Lock()
head := &pool.head
if head.next == nil {
pool.Unlock()
return pool.alloc()
}
ret := head.next
head.next = ret.next
if ret == pool.tail {
pool.tail = head
}
pool.count--
pool.Unlock()
ret.next = nil
return ret
}
func (pool *Pool) put(p *goroutine) {
p.next = nil
pool.Lock()
pool.tail.next = p
pool.tail = p
pool.count++
pool.Unlock()
pool.gcWorker.RLock()
gcWorker := pool.gcWorker.value
pool.gcWorker.RUnlock()
if !gcWorker {
go pool.gcLoop()
}
}
func (pool *Pool) alloc() *goroutine {
g := &goroutine{
ch: make(chan func()),
pool: pool,
}
go func(g *goroutine) {
for work := range g.ch {
work()
g.lastRun = time.Now()
// Put g back to the pool.
// This is the normal usage for a resource pool:
//
// obj := pool.get()
// use(obj)
// pool.put(obj)
//
// But when goroutine is used as a resource, we can't pool.put() immediately,
// because the resource(goroutine) maybe still in use.
// So, put back resource is done here, when the goroutine finish its work.
pool.put(g)
}
}(g)
return g
}
func (pool *Pool) gcLoop() {
pool.gcWorker.Lock()
if pool.gcWorker.value == true {
pool.gcWorker.Unlock()
return
}
pool.gcWorker.value = true
pool.gcWorker.Unlock()
for {
finish, more := pool.gcOnce(30)
if finish {
pool.gcWorker.Lock()
pool.gcWorker.value = false
pool.gcWorker.Unlock()
return
}
if more {
time.Sleep(min(pool.idleTimeout/10, 500*time.Millisecond))
} else {
time.Sleep(min(5*time.Second, pool.idleTimeout/3))
}
}
}
// gcOnce runs gc once, recycles at most count goroutines.
// finish indicates there're no more goroutines in the pool after gc,
// more indicates there're still many goroutines to be recycled.
func (pool *Pool) gcOnce(count int) (finish bool, more bool) {
now := time.Now()
i := 0
pool.Lock()
head := &pool.head
for head.next != nil && i < count {
save := head.next
duration := now.Sub(save.lastRun)
if duration < pool.idleTimeout {
break
}
close(save.ch)
head.next = save.next
pool.count--
i++
}
if head.next == nil {
finish = true
pool.tail = head
}
pool.Unlock()
more = (i == count)
return
}
func min(a, b time.Duration) time.Duration {
if a < b {
return a
}
return b
}