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// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// GOMAXPROCS=10 go test
// This is a copy of sync/rwmutex_test.go rewritten to test the
// runtime rwmutex.
package runtime_test
import (
"fmt"
. "runtime"
"runtime/debug"
"sync/atomic"
"testing"
)
func parallelReader(m *RWMutex, clocked chan bool, cunlock *atomic.Bool, cdone chan bool) {
m.RLock()
clocked <- true
for !cunlock.Load() {
}
m.RUnlock()
cdone <- true
}
func doTestParallelReaders(numReaders int) {
GOMAXPROCS(numReaders + 1)
var m RWMutex
m.Init()
clocked := make(chan bool, numReaders)
var cunlock atomic.Bool
cdone := make(chan bool)
for i := 0; i < numReaders; i++ {
go parallelReader(&m, clocked, &cunlock, cdone)
}
// Wait for all parallel RLock()s to succeed.
for i := 0; i < numReaders; i++ {
<-clocked
}
cunlock.Store(true)
// Wait for the goroutines to finish.
for i := 0; i < numReaders; i++ {
<-cdone
}
}
func TestParallelRWMutexReaders(t *testing.T) {
if GOARCH == "wasm" {
t.Skip("wasm has no threads yet")
}
defer GOMAXPROCS(GOMAXPROCS(-1))
// If runtime triggers a forced GC during this test then it will deadlock,
// since the goroutines can't be stopped/preempted.
// Disable GC for this test (see issue #10958).
defer debug.SetGCPercent(debug.SetGCPercent(-1))
// SetGCPercent waits until the mark phase is over, but the runtime
// also preempts at the start of the sweep phase, so make sure that's
// done too.
GC()
doTestParallelReaders(1)
doTestParallelReaders(3)
doTestParallelReaders(4)
}
func reader(rwm *RWMutex, num_iterations int, activity *int32, cdone chan bool) {
for i := 0; i < num_iterations; i++ {
rwm.RLock()
n := atomic.AddInt32(activity, 1)
if n < 1 || n >= 10000 {
panic(fmt.Sprintf("wlock(%d)\n", n))
}
for i := 0; i < 100; i++ {
}
atomic.AddInt32(activity, -1)
rwm.RUnlock()
}
cdone <- true
}
func writer(rwm *RWMutex, num_iterations int, activity *int32, cdone chan bool) {
for i := 0; i < num_iterations; i++ {
rwm.Lock()
n := atomic.AddInt32(activity, 10000)
if n != 10000 {
panic(fmt.Sprintf("wlock(%d)\n", n))
}
for i := 0; i < 100; i++ {
}
atomic.AddInt32(activity, -10000)
rwm.Unlock()
}
cdone <- true
}
func HammerRWMutex(gomaxprocs, numReaders, num_iterations int) {
GOMAXPROCS(gomaxprocs)
// Number of active readers + 10000 * number of active writers.
var activity int32
var rwm RWMutex
rwm.Init()
cdone := make(chan bool)
go writer(&rwm, num_iterations, &activity, cdone)
var i int
for i = 0; i < numReaders/2; i++ {
go reader(&rwm, num_iterations, &activity, cdone)
}
go writer(&rwm, num_iterations, &activity, cdone)
for ; i < numReaders; i++ {
go reader(&rwm, num_iterations, &activity, cdone)
}
// Wait for the 2 writers and all readers to finish.
for i := 0; i < 2+numReaders; i++ {
<-cdone
}
}
func TestRWMutex(t *testing.T) {
defer GOMAXPROCS(GOMAXPROCS(-1))
n := 1000
if testing.Short() {
n = 5
}
HammerRWMutex(1, 1, n)
HammerRWMutex(1, 3, n)
HammerRWMutex(1, 10, n)
HammerRWMutex(4, 1, n)
HammerRWMutex(4, 3, n)
HammerRWMutex(4, 10, n)
HammerRWMutex(10, 1, n)
HammerRWMutex(10, 3, n)
HammerRWMutex(10, 10, n)
HammerRWMutex(10, 5, n)
}
func BenchmarkRWMutexUncontended(b *testing.B) {
type PaddedRWMutex struct {
RWMutex
pad [32]uint32
}
b.RunParallel(func(pb *testing.PB) {
var rwm PaddedRWMutex
rwm.Init()
for pb.Next() {
rwm.RLock()
rwm.RLock()
rwm.RUnlock()
rwm.RUnlock()
rwm.Lock()
rwm.Unlock()
}
})
}
func benchmarkRWMutex(b *testing.B, localWork, writeRatio int) {
var rwm RWMutex
rwm.Init()
b.RunParallel(func(pb *testing.PB) {
foo := 0
for pb.Next() {
foo++
if foo%writeRatio == 0 {
rwm.Lock()
rwm.Unlock()
} else {
rwm.RLock()
for i := 0; i != localWork; i += 1 {
foo *= 2
foo /= 2
}
rwm.RUnlock()
}
}
_ = foo
})
}
func BenchmarkRWMutexWrite100(b *testing.B) {
benchmarkRWMutex(b, 0, 100)
}
func BenchmarkRWMutexWrite10(b *testing.B) {
benchmarkRWMutex(b, 0, 10)
}
func BenchmarkRWMutexWorkWrite100(b *testing.B) {
benchmarkRWMutex(b, 100, 100)
}
func BenchmarkRWMutexWorkWrite10(b *testing.B) {
benchmarkRWMutex(b, 100, 10)
}
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