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util/goroutine_pool: add a goroutine pool package utilities #3752
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,181 @@ | ||
// Copyright 2016 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" | ||
"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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// 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 | ||
} | ||
} | ||
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// 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 | ||
} | ||
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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()) { | ||
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. | ||
} | ||
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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 { | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more.
is easier to read. There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. I didn't intent to maintain count, it's added later just for testing purpose. |
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pool.tail = head | ||
} | ||
pool.count-- | ||
pool.Unlock() | ||
ret.next = nil | ||
return ret | ||
} | ||
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func (pool *Pool) put(p *goroutine) { | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. This is called by |
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p.next = nil | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Isn't it always nil, encured by |
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pool.Lock() | ||
pool.tail.next = p | ||
pool.tail = p | ||
pool.count++ | ||
pool.Unlock() | ||
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pool.gcWorker.RLock() | ||
gcWorker := pool.gcWorker.value | ||
pool.gcWorker.RUnlock() | ||
if !gcWorker { | ||
go pool.gcLoop() | ||
} | ||
} | ||
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func (pool *Pool) alloc() *goroutine { | ||
g := &goroutine{ | ||
ch: make(chan func()), | ||
pool: pool, | ||
} | ||
go func(g *goroutine) { | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. I think defining a method for |
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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 | ||
} | ||
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func (pool *Pool) gcLoop() { | ||
pool.gcWorker.Lock() | ||
if pool.gcWorker.value == true { | ||
pool.gcWorker.Unlock() | ||
return | ||
} | ||
pool.gcWorker.value = true | ||
pool.gcWorker.Unlock() | ||
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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)) | ||
} | ||
} | ||
} | ||
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// 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 | ||
} | ||
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func min(a, b time.Duration) time.Duration { | ||
if a < b { | ||
return a | ||
} | ||
return b | ||
} |
Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,131 @@ | ||
// Copyright 2016 PingCAP, Inc. | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. 2016 -> 2017 |
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// | ||
// 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.Lock() | ||
count := gp.count | ||
gp.Unlock() | ||
if count != 0 { | ||
t.Error("all goroutines should be recycled") | ||
} | ||
} | ||
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func TestRace(t *testing.T) { | ||
gp := New(200 * time.Millisecond) | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Isn't the timeout too long to test race? |
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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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2016 -> 2017