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Bug 1787974 - TimerThread stores Entry's instead of UniquePtrs to Entry's r=smaug

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This removes memory heap allocations and deallocations, and indirections to access entries.

Differential Revision: https://phabricator.services.mozilla.com/D164287
This commit is contained in:
Gerald Squelart 2023-01-20 17:11:09 +00:00
parent 38ae7225cd
commit 2254f41c15
2 changed files with 31 additions and 23 deletions
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39
xpcom/threads/TimerThread.cpp
View File

@ -427,8 +427,9 @@ nsresult TimerThread::Shutdown() {
// might potentially call some code reentering the same lock
// that leads to unexpected behavior or deadlock.
// See bug 422472.
for (const UniquePtr<Entry>& entry : mTimers) {
timers.AppendElement(entry->Take());
timers.SetCapacity(mTimers.Length());
for (Entry& entry : mTimers) {
timers.AppendElement(entry.Take());
}
mTimers.Clear();
@ -510,7 +511,7 @@ TimerThread::Run() {
RemoveLeadingCanceledTimersInternal();
if (!mTimers.IsEmpty()) {
if (now >= mTimers[0]->Value()->mTimeout || forceRunThisTimer) {
if (now >= mTimers[0].Value()->mTimeout || forceRunThisTimer) {
next:
// NB: AddRef before the Release under RemoveTimerInternal to avoid
// mRefCnt passing through zero, in case all other refs than the one
@ -518,7 +519,7 @@ TimerThread::Run() {
// must be racing with us, blocked in gThread->RemoveTimer waiting
// for TimerThread::mMonitor, under nsTimerImpl::Release.
RefPtr<nsTimerImpl> timerRef(mTimers[0]->Take());
RefPtr<nsTimerImpl> timerRef(mTimers[0].Take());
RemoveFirstTimerInternal();
MOZ_LOG(GetTimerLog(), LogLevel::Debug,
@ -546,7 +547,7 @@ TimerThread::Run() {
RemoveLeadingCanceledTimersInternal();
if (!mTimers.IsEmpty()) {
TimeStamp timeout = mTimers[0]->Value()->mTimeout;
TimeStamp timeout = mTimers[0].Value()->mTimeout;
// Don't wait at all (even for PR_INTERVAL_NO_WAIT) if the next timer
// is due now or overdue.
@ -630,7 +631,7 @@ nsresult TimerThread::AddTimer(nsTimerImpl* aTimer,
// systems there could be a significant delay compared to notifying, which
// is almost immediate; and some users of 0-delay depend on it being this
// fast!
if (mWaiting && (mTimers[0]->Value() == aTimer || aTimer->mDelay.IsZero())) {
if (mWaiting && (mTimers[0].Value() == aTimer || aTimer->mDelay.IsZero())) {
mNotified = true;
mMonitor.Notify();
}
@ -732,14 +733,14 @@ TimeStamp TimerThread::FindNextFireTimeForCurrentThread(TimeStamp aDefault,
TimeStamp firstTimeStamp;
Entry* initialFirstEntry = nullptr;
if (!mTimers.IsEmpty()) {
initialFirstEntry = mTimers[0].get();
firstTimeStamp = mTimers[0]->Timeout();
initialFirstEntry = &mTimers[0];
firstTimeStamp = mTimers[0].Timeout();
}
#endif
auto end = mTimers.end();
while (end != mTimers.begin()) {
nsTimerImpl* timer = mTimers[0]->Value();
nsTimerImpl* timer = mTimers[0].Value();
if (timer) {
if (timer->mTimeout > aDefault) {
timeStamp = aDefault;
@ -779,17 +780,17 @@ TimeStamp TimerThread::FindNextFireTimeForCurrentThread(TimeStamp aDefault,
#ifdef DEBUG
if (!mTimers.IsEmpty()) {
if (firstTimeStamp != mTimers[0]->Timeout()) {
if (firstTimeStamp != mTimers[0].Timeout()) {
TimeStamp now = TimeStamp::Now();
printf_stderr(
"firstTimeStamp %f, mTimers[0]->Timeout() %f, "
"firstTimeStamp %f, mTimers[0].Timeout() %f, "
"initialFirstTimer %p, current first %p\n",
(firstTimeStamp - now).ToMilliseconds(),
(mTimers[0]->Timeout() - now).ToMilliseconds(), initialFirstEntry,
mTimers[0].get());
(mTimers[0].Timeout() - now).ToMilliseconds(), initialFirstEntry,
&mTimers[0]);
}
}
MOZ_ASSERT_IF(!mTimers.IsEmpty(), firstTimeStamp == mTimers[0]->Timeout());
MOZ_ASSERT_IF(!mTimers.IsEmpty(), firstTimeStamp == mTimers[0].Timeout());
#endif
return timeStamp;
@ -809,8 +810,8 @@ bool TimerThread::AddTimerInternal(nsTimerImpl* aTimer) {
LogTimerEvent::LogDispatch(aTimer);
UniquePtr<Entry>* entry = mTimers.AppendElement(
MakeUnique<Entry>(now, aTimer->mTimeout, aTimer), mozilla::fallible);
Entry* entry =
mTimers.EmplaceBack(mozilla::fallible, now, aTimer->mTimeout, aTimer);
if (!entry) {
return false;
}
@ -836,8 +837,8 @@ bool TimerThread::RemoveTimerInternal(nsTimerImpl* aTimer) {
}
AUTO_TIMERS_STATS(TimerThread_RemoveTimerInternal_in_list);
for (auto& entry : mTimers) {
if (entry->Value() == aTimer) {
entry->Forget(aTimer);
if (entry.Value() == aTimer) {
entry.Forget(aTimer);
return true;
}
}
@ -855,7 +856,7 @@ void TimerThread::RemoveLeadingCanceledTimersInternal() {
// without actually removing them from the list so we can
// modify the nsTArray in a single bulk operation.
auto sortedEnd = mTimers.end();
while (sortedEnd != mTimers.begin() && !mTimers[0]->Value()) {
while (sortedEnd != mTimers.begin() && !mTimers[0].Value()) {
std::pop_heap(mTimers.begin(), sortedEnd, Entry::UniquePtrLessThan);
--sortedEnd;
}

15
xpcom/threads/TimerThread.h
View File

@ -96,6 +96,14 @@ class TimerThread final : public mozilla::Runnable, public nsIObserver {
}
}
// Don't allow copies, otherwise which one would manage `IsInTimerThread`?
Entry(const Entry&) = delete;
Entry& operator=(const Entry&) = delete;
// Move-only.
Entry(Entry&&) = default;
Entry& operator=(Entry&&) = default;
~Entry() {
if (mTimerImpl) {
mTimerImpl->mMutex.AssertCurrentThreadOwns();
@ -124,11 +132,10 @@ class TimerThread final : public mozilla::Runnable, public nsIObserver {
return mTimerImpl.forget();
}
static bool UniquePtrLessThan(mozilla::UniquePtr<Entry>& aLeft,
mozilla::UniquePtr<Entry>& aRight) {
static bool UniquePtrLessThan(const Entry& aLeft, const Entry& aRight) {
// This is reversed because std::push_heap() sorts the "largest" to
// the front of the heap. We want that to be the earliest timer.
return aRight->mTimeout < aLeft->mTimeout;
return aRight.mTimeout < aLeft.mTimeout;
}
const TimeStamp& Timeout() const { return mTimeout; }
@ -138,7 +145,7 @@ class TimerThread final : public mozilla::Runnable, public nsIObserver {
TimeStamp mTimeout;
};
nsTArray<mozilla::UniquePtr<Entry>> mTimers MOZ_GUARDED_BY(mMonitor);
nsTArray<Entry> mTimers MOZ_GUARDED_BY(mMonitor);
// Set only at the start of the thread's Run():
uint32_t mAllowedEarlyFiringMicroseconds MOZ_GUARDED_BY(mMonitor);
ProfilerThreadId mProfilerThreadId MOZ_GUARDED_BY(mMonitor);