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-rw-r--r--src/runtime/rwmutex_test.go195
1 files changed, 195 insertions, 0 deletions
diff --git a/src/runtime/rwmutex_test.go b/src/runtime/rwmutex_test.go
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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)
+}