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util/goroutine_pool: add a goroutine pool package utilities #3752
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util/goroutine_pool: add a goroutine pool package utilities
tiancaiamao 1592c7b
address comment
tiancaiamao f24850f
remove gcWorker
tiancaiamao 25665dc
address comment
tiancaiamao d62f92f
address comment
tiancaiamao 3fd1c58
address comment
tiancaiamao 6edd144
address comment
tiancaiamao ecf54ca
Merge branch 'master' into goroutine-pool
tiancaiamao 0b5007a
Merge branch 'master' into tiancaiamao/goroutine-pool
coocood 4a5a8f9
Merge branch 'master' into tiancaiamao/goroutine-pool
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// 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. | ||
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package gp | ||
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import ( | ||
"sync" | ||
"sync/atomic" | ||
"time" | ||
) | ||
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// Pool is a struct to represent goroutine pool. | ||
type Pool struct { | ||
head goroutine | ||
tail *goroutine | ||
count int | ||
idleTimeout time.Duration | ||
sync.Mutex | ||
} | ||
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// goroutine is actually a background goroutine, with a channel binded for communication. | ||
type goroutine struct { | ||
ch chan func() | ||
next *goroutine | ||
status int32 | ||
} | ||
|
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const ( | ||
statusIdle int32 = 0 | ||
statusInUse int32 = 1 | ||
statusDead int32 = 2 | ||
) | ||
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// New returns a new *Pool object. | ||
func New(idleTimeout time.Duration) *Pool { | ||
pool := &Pool{ | ||
idleTimeout: idleTimeout, | ||
} | ||
pool.tail = &pool.head | ||
return pool | ||
} | ||
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// 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()) { | ||
for { | ||
g := pool.get() | ||
if atomic.CompareAndSwapInt32(&g.status, statusIdle, statusInUse) { | ||
g.ch <- f | ||
return | ||
} | ||
// Status already changed from statusIdle => statusDead, drop it, find next one. | ||
} | ||
} | ||
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func (pool *Pool) get() *goroutine { | ||
pool.Lock() | ||
head := &pool.head | ||
if head.next == nil { | ||
pool.Unlock() | ||
return pool.alloc() | ||
} | ||
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ret := head.next | ||
head.next = ret.next | ||
if ret == pool.tail { | ||
pool.tail = head | ||
} | ||
pool.count-- | ||
pool.Unlock() | ||
ret.next = nil | ||
return ret | ||
} | ||
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func (pool *Pool) alloc() *goroutine { | ||
g := &goroutine{ | ||
ch: make(chan func()), | ||
} | ||
go g.workLoop(pool) | ||
return g | ||
} | ||
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func (g *goroutine) put(pool *Pool) { | ||
g.status = statusIdle | ||
pool.Lock() | ||
pool.tail.next = g | ||
pool.tail = g | ||
pool.count++ | ||
pool.Unlock() | ||
} | ||
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func (g *goroutine) workLoop(pool *Pool) { | ||
timer := time.NewTimer(pool.idleTimeout) | ||
for { | ||
select { | ||
case <-timer.C: | ||
// Check to avoid a corner case that the goroutine is take out from pool, | ||
// and get this signal at the same time. | ||
succ := atomic.CompareAndSwapInt32(&g.status, statusIdle, statusDead) | ||
if succ { | ||
return | ||
} | ||
case work := <-g.ch: | ||
work() | ||
// 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. | ||
g.put(pool) | ||
} | ||
timer.Reset(pool.idleTimeout) | ||
} | ||
} |
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@@ -0,0 +1,132 @@ | ||
// 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. | ||
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package gp | ||
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import ( | ||
"sync" | ||
"testing" | ||
"time" | ||
) | ||
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func TestBasicAPI(t *testing.T) { | ||
gp := New(time.Second) | ||
var wg sync.WaitGroup | ||
wg.Add(1) | ||
// cover alloc() | ||
gp.Go(func() { wg.Done() }) | ||
// cover put() | ||
wg.Wait() | ||
// cover get() | ||
gp.Go(func() {}) | ||
} | ||
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func TestGC(t *testing.T) { | ||
gp := New(200 * time.Millisecond) | ||
var wg sync.WaitGroup | ||
wg.Add(100) | ||
for i := 0; i < 100; i++ { | ||
idx := i | ||
gp.Go(func() { | ||
time.Sleep(time.Duration(idx+1) * time.Millisecond) | ||
wg.Done() | ||
}) | ||
} | ||
wg.Wait() | ||
time.Sleep(300 * time.Millisecond) | ||
gp.Go(func() {}) // To trigger count change. | ||
gp.Lock() | ||
count := gp.count | ||
gp.Unlock() | ||
if count > 1 { | ||
t.Error("all goroutines should be recycled", count) | ||
} | ||
} | ||
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func TestRace(t *testing.T) { | ||
gp := New(8 * time.Millisecond) | ||
var wg sync.WaitGroup | ||
begin := make(chan struct{}) | ||
wg.Add(500) | ||
for i := 0; i < 50; i++ { | ||
go func() { | ||
<-begin | ||
for i := 0; i < 10; i++ { | ||
gp.Go(func() { | ||
wg.Done() | ||
}) | ||
time.Sleep(5 * time.Millisecond) | ||
} | ||
}() | ||
} | ||
close(begin) | ||
wg.Wait() | ||
} | ||
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func BenchmarkGoPool(b *testing.B) { | ||
gp := New(20 * time.Second) | ||
for i := 0; i < b.N/2; i++ { | ||
gp.Go(func() {}) | ||
} | ||
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b.ResetTimer() | ||
for i := 0; i < b.N; i++ { | ||
gp.Go(dummy) | ||
} | ||
} | ||
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func BenchmarkGo(b *testing.B) { | ||
b.ResetTimer() | ||
for i := 0; i < b.N; i++ { | ||
go dummy() | ||
} | ||
} | ||
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func dummy() { | ||
} | ||
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func BenchmarkMorestackPool(b *testing.B) { | ||
gp := New(5 * time.Second) | ||
b.ResetTimer() | ||
for i := 0; i < b.N; i++ { | ||
var wg sync.WaitGroup | ||
wg.Add(1) | ||
gp.Go(func() { | ||
morestack(false) | ||
wg.Done() | ||
}) | ||
wg.Wait() | ||
} | ||
} | ||
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func BenchmarkMoreStack(b *testing.B) { | ||
b.ResetTimer() | ||
for i := 0; i < b.N; i++ { | ||
var wg sync.WaitGroup | ||
wg.Add(1) | ||
go func() { | ||
morestack(false) | ||
wg.Done() | ||
}() | ||
wg.Wait() | ||
} | ||
} | ||
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func morestack(f bool) { | ||
var stack [8 * 1024]byte | ||
if f { | ||
for i := 0; i < len(stack); i++ { | ||
stack[i] = 'a' | ||
} | ||
} | ||
} |
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is easier to read.
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I didn't intent to maintain count, it's added later just for testing purpose.