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Revert "runtime: improve runtime-internal mutex profile tests"

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This reverts commit f9ba2cff22 (CL 586237)

Reason for revert: This is part of a patch series that changed the
handling of contended lock2/unlock2 calls, reducing the maximum
throughput of contended runtime.mutex values, and causing a performance
regression on applications where that is (or became) the bottleneck.

This test verifies that the semantics of the mutex profile for
runtime.mutex values matches that of sync.Mutex values. Without the rest
of the patch series, this test would correctly identify that Go 1.22's
semantics are incorrect (issue #66999).

Updates #66999
Updates #67585

Change-Id: Id06ae01d7bc91c94054c80d273e6530cb2d59d10
Reviewed-on: https://go-review.googlesource.com/c/go/+/589096
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Auto-Submit: Rhys Hiltner <rhys.hiltner@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Rhys Hiltner 2024-05-29 16:39:34 +00:00 committed by Gopher Robot
parent 1be701a344
commit e6b8b2f3e2
2 changed files with 29 additions and 148 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/runtime/export_test.go
View File

@ -39,8 +39,6 @@ var Atoi32 = atoi32
var ParseByteCount = parseByteCount
var Nanotime = nanotime
var Cputicks = cputicks
var CyclesPerSecond = pprof_cyclesPerSecond
var NetpollBreak = netpollBreak
var Usleep = usleep

175
src/runtime/metrics_test.go
View File

@ -1008,9 +1008,9 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
return metricGrowth, profileGrowth, p
}
testcase := func(strictTiming bool, acceptStacks [][]string, workers int, fn func() bool) func(t *testing.T) (metricGrowth float64, profileGrowth []int64, n, value int64) {
return func(t *testing.T) (metricGrowth float64, profileGrowth []int64, n, value int64) {
metricGrowth, totalProfileGrowth, p := measureDelta(t, func() {
testcase := func(strictTiming bool, acceptStacks [][]string, workers int, fn func() bool) func(t *testing.T) (metricGrowth, profileGrowth float64, n, value int64) {
return func(t *testing.T) (metricGrowth, profileGrowth float64, n, value int64) {
metricGrowth, profileGrowth, p := measureDelta(t, func() {
var started, stopped sync.WaitGroup
started.Add(workers)
stopped.Add(workers)
@ -1030,7 +1030,7 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
stopped.Wait()
})
if totalProfileGrowth == 0 {
if profileGrowth == 0 {
t.Errorf("no increase in mutex profile")
}
if metricGrowth == 0 && strictTiming {
@ -1050,7 +1050,7 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
// together. It doesn't work as well for user-space contention, where the
// involved goroutines are not _Grunnable the whole time and so need to pass
// through the scheduler.
t.Logf("lock contention growth in runtime/pprof's view (%fs)", totalProfileGrowth)
t.Logf("lock contention growth in runtime/pprof's view (%fs)", profileGrowth)
t.Logf("lock contention growth in runtime/metrics' view (%fs)", metricGrowth)
acceptStacks = append([][]string(nil), acceptStacks...)
@ -1070,7 +1070,7 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
}
var stks [][]string
values := make([][2]int64, len(acceptStacks)+1)
values := make([][2]int64, len(acceptStacks))
for _, s := range p.Sample {
var have []string
for _, loc := range s.Location {
@ -1079,26 +1079,16 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
}
}
stks = append(stks, have)
found := false
for i, stk := range acceptStacks {
if slices.Equal(have, stk) {
values[i][0] += s.Value[0]
values[i][1] += s.Value[1]
found = true
break
}
}
if !found {
values[len(values)-1][0] += s.Value[0]
values[len(values)-1][1] += s.Value[1]
}
}
profileGrowth = make([]int64, len(acceptStacks)+1)
profileGrowth[len(profileGrowth)-1] = values[len(values)-1][1]
for i, stk := range acceptStacks {
n += values[i][0]
value += values[i][1]
profileGrowth[i] = values[i][1]
t.Logf("stack %v has samples totaling n=%d value=%d", stk, values[i][0], values[i][1])
}
if n == 0 && value == 0 {
@ -1120,14 +1110,8 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
t.Run("runtime.lock", func(t *testing.T) {
mus := make([]runtime.Mutex, 200)
var needContention atomic.Int64
baseDelay := 100 * time.Microsecond // large relative to system noise, for comparison between clocks
fastDelayMicros := baseDelay.Microseconds()
slowDelayMicros := baseDelay.Microseconds() * 4
const (
fastRole = 0
slowRole = 1
)
delay := 100 * time.Microsecond // large relative to system noise, for comparison between clocks
delayMicros := delay.Microseconds()
// The goroutine that acquires the lock will only proceed when it
// detects that its partner is contended for the lock. That will lead to
@ -1143,13 +1127,6 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
t.Skipf("contention on runtime-internal locks requires GOMAXPROCS >= %d", workers)
}
minTicks := make([][]int64, workers) // lower bound, known-contended time, measured by cputicks
maxTicks := make([][]int64, workers) // upper bound, total lock() duration, measured by cputicks
for i := range minTicks {
minTicks[i] = make([]int64, len(mus))
maxTicks[i] = make([]int64, len(mus))
}
var id atomic.Int32
fn := func() bool {
n := int(needContention.Load())
if n < 0 {
@ -1157,55 +1134,27 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
}
mu := &mus[n]
// Each worker has a role: to have a fast or slow critical section.
// Rotate the role assignments as we step through the mutex slice so
// we don't end up with one M always claiming the same kind of work.
id := int(id.Add(1))
role := (id + n) % workers
marker, delayMicros := fastMarkerFrame, fastDelayMicros
if role == slowRole {
marker, delayMicros = slowMarkerFrame, slowDelayMicros
}
marker(func() {
t0 := runtime.Cputicks()
runtime.Lock(mu)
maxTicks[role][n] = runtime.Cputicks() - t0
minTicks[role][n] = 0
for int(needContention.Load()) == n {
if runtime.MutexContended(mu) {
t1 := runtime.Cputicks()
// make them wait a little while
for start := runtime.Nanotime(); (runtime.Nanotime()-start)/1000 < delayMicros; {
runtime.Usleep(uint32(1 + delayMicros/8))
}
minTicks[role][n] = runtime.Cputicks() - t1
break
runtime.Lock(mu)
for int(needContention.Load()) == n {
if runtime.MutexContended(mu) {
// make them wait a little while
for start := runtime.Nanotime(); (runtime.Nanotime()-start)/1000 < delayMicros; {
runtime.Usleep(uint32(delayMicros))
}
break
}
runtime.Unlock(mu)
needContention.Store(int64(n - 1))
})
}
runtime.Unlock(mu)
needContention.Store(int64(n - 1))
return true
}
stks := make([][]string, 2)
for i := range stks {
marker := "runtime_test.fastMarkerFrame"
if i == slowRole {
marker = "runtime_test.slowMarkerFrame"
}
stks[i] = []string{
"runtime.unlock",
"runtime_test." + name + ".func4.1.1",
marker,
"runtime_test." + name + ".func4.1",
"runtime_test.(*contentionWorker).run",
}
}
stks := [][]string{{
"runtime.unlock",
"runtime_test." + name + ".func4.1",
"runtime_test.(*contentionWorker).run",
}}
t.Run("sample-1", func(t *testing.T) {
old := runtime.SetMutexProfileFraction(1)
@ -1215,11 +1164,11 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
metricGrowth, profileGrowth, n, _ := testcase(true, stks, workers, fn)(t)
t.Run("metric", func(t *testing.T) {
// The runtime/metrics view is sampled at 1 per gTrackingPeriod,
// so we don't have a hard lower bound here.
// The runtime/metrics view may be sampled at 1 per
// gTrackingPeriod, so we don't have a hard lower bound here.
testenv.SkipFlaky(t, 64253)
if have, want := metricGrowth, baseDelay.Seconds()*float64(len(mus)); have < want {
if have, want := metricGrowth, delay.Seconds()*float64(len(mus)); have < want {
// The test imposes a delay with usleep, verified with calls to
// nanotime. Compare against the runtime/metrics package's view
// (based on nanotime) rather than runtime/pprof's view (based
@ -1231,68 +1180,10 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
t.Errorf("mutex profile reported contention count different from the known true count (%d != %d)", have, want)
}
var slowMinTicks, fastMinTicks int64
for role, ticks := range minTicks {
for _, delta := range ticks {
if role == slowRole {
slowMinTicks += delta
} else {
fastMinTicks += delta
}
}
}
var slowMaxTicks, fastMaxTicks int64
for role, ticks := range maxTicks {
for _, delta := range ticks {
if role == slowRole {
slowMaxTicks += delta
} else {
fastMaxTicks += delta
}
}
}
cpuGHz := float64(runtime.CyclesPerSecond()) / 1e9
for _, set := range []struct {
name string
profTime int64
minTime int64
maxTime int64
}{
{
name: "slow",
profTime: profileGrowth[slowRole],
minTime: int64(float64(slowMinTicks) / cpuGHz),
maxTime: int64(float64(fastMaxTicks) / cpuGHz),
},
{
name: "fast",
profTime: profileGrowth[fastRole],
minTime: int64(float64(fastMinTicks) / cpuGHz),
maxTime: int64(float64(slowMaxTicks) / cpuGHz),
},
} {
t.Logf("profile's view of delays due to %q critical section: %dns", set.name, set.profTime)
t.Logf("test's view of known-contended time within %q critical section: %dns", set.name, set.minTime)
t.Logf("test's view of lock duration before critical sections other than %q: %dns", set.name, set.maxTime)
if set.profTime < set.minTime {
t.Errorf("profile undercounted %q critical section", set.name)
}
if set.profTime > set.maxTime {
t.Errorf("profile overcounted %q critical section", set.name)
}
}
var totalProfileGrowth float64
for _, growth := range profileGrowth {
totalProfileGrowth += float64(growth) * time.Nanosecond.Seconds()
}
const slop = 1.5 // account for nanotime vs cputicks
t.Run("compare timers", func(t *testing.T) {
testenv.SkipFlaky(t, 64253)
if totalProfileGrowth > slop*metricGrowth || metricGrowth > slop*totalProfileGrowth {
if profileGrowth > slop*metricGrowth || metricGrowth > slop*profileGrowth {
t.Errorf("views differ by more than %fx", slop)
}
})
@ -1313,7 +1204,7 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
// 1e-9 chance of that, which is an acceptably low flakiness rate.
const samplingSlop = 2.5
if have, want := metricGrowth, baseDelay.Seconds()*float64(len(mus)); samplingSlop*have < want {
if have, want := metricGrowth, delay.Seconds()*float64(len(mus)); samplingSlop*have < want {
// The test imposes a delay with usleep, verified with calls to
// nanotime. Compare against the runtime/metrics package's view
// (based on nanotime) rather than runtime/pprof's view (based
@ -1324,13 +1215,8 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
t.Errorf("mutex profile reported contention count too different from the expected count (%d far from %d)", have, want)
}
var totalProfileGrowth float64
for _, growth := range profileGrowth {
totalProfileGrowth += float64(growth) * time.Nanosecond.Seconds()
}
const timerSlop = 1.5 * samplingSlop // account for nanotime vs cputicks, plus the two views' independent sampling
if totalProfileGrowth > timerSlop*metricGrowth || metricGrowth > timerSlop*totalProfileGrowth {
if profileGrowth > timerSlop*metricGrowth || metricGrowth > timerSlop*profileGrowth {
t.Errorf("views differ by more than %fx", timerSlop)
}
})
@ -1397,9 +1283,6 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) {
})
}
func slowMarkerFrame(fn func()) { fn() }
func fastMarkerFrame(fn func()) { fn() }
// contentionWorker provides cleaner call stacks for lock contention profile tests
type contentionWorker struct {
before func()