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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
#include "mozilla/StaticPrefs_page_load.h"
#include "mozilla/StaticPrefs_javascript.h"
#include "mozilla/Unused.h"
#include "mozilla/ipc/IdleSchedulerParent.h"
#include "mozilla/AppShutdown.h"
#include "mozilla/Telemetry.h"
#include "nsSystemInfo.h"
#include "nsThreadUtils.h"
#include "nsITimer.h"
#include "nsIThread.h"
namespace mozilla::ipc {
MOZ_RUNINIT RefPtr<SharedMemory> IdleSchedulerParent::sActiveChildCounter =
nullptr;
std::bitset<NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT>
IdleSchedulerParent::sInUseChildCounters;
MOZ_RUNINIT LinkedList<IdleSchedulerParent>
IdleSchedulerParent::sIdleAndGCRequests;
int32_t IdleSchedulerParent::sMaxConcurrentIdleTasksInChildProcesses = 1;
uint32_t IdleSchedulerParent::sMaxConcurrentGCs = 1;
uint32_t IdleSchedulerParent::sActiveGCs = 0;
uint32_t IdleSchedulerParent::sChildProcessesRunningPrioritizedOperation = 0;
uint32_t IdleSchedulerParent::sChildProcessesAlive = 0;
nsITimer* IdleSchedulerParent::sStarvationPreventer = nullptr;
uint32_t IdleSchedulerParent::sNumCPUs = 0;
uint32_t IdleSchedulerParent::sPrefConcurrentGCsMax = 0;
uint32_t IdleSchedulerParent::sPrefConcurrentGCsCPUDivisor = 0;
IdleSchedulerParent::IdleSchedulerParent() {
MOZ_ASSERT(!AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMShutdownThreads));
sChildProcessesAlive++;
uint32_t max_gcs_pref =
StaticPrefs::javascript_options_concurrent_multiprocess_gcs_max();
uint32_t cpu_divisor_pref =
StaticPrefs::javascript_options_concurrent_multiprocess_gcs_cpu_divisor();
if (!max_gcs_pref) {
max_gcs_pref = UINT32_MAX;
}
if (!cpu_divisor_pref) {
cpu_divisor_pref = 4;
}
if (!sNumCPUs) {
// While waiting for the real logical core count behave as if there was
// just one core.
sNumCPUs = 1;
// nsISystemInfo can be initialized only on the main thread.
nsCOMPtr<nsIThread> thread = do_GetCurrentThread();
nsCOMPtr<nsIRunnable> runnable =
NS_NewRunnableFunction("cpucount getter", [thread]() {
ProcessInfo processInfo = {};
if (NS_SUCCEEDED(CollectProcessInfo(processInfo))) {
uint32_t num_cpus = processInfo.cpuCount;
// We have a new cpu count, Update the number of idle tasks.
if (MOZ_LIKELY(!AppShutdown::IsInOrBeyond(
ShutdownPhase::XPCOMShutdownThreads))) {
nsCOMPtr<nsIRunnable> runnable = NS_NewRunnableFunction(
"IdleSchedulerParent::CalculateNumIdleTasks", [num_cpus]() {
// We're setting this within this lambda because it's run on
// the correct thread and avoids a race.
sNumCPUs = num_cpus;
// This reads the sPrefConcurrentGCsMax and
// sPrefConcurrentGCsCPUDivisor values set below, it will
// run after the code that sets those.
CalculateNumIdleTasks();
});
thread->Dispatch(runnable, NS_DISPATCH_NORMAL);
}
}
});
NS_DispatchBackgroundTask(runnable.forget(), NS_DISPATCH_EVENT_MAY_BLOCK);
}
if (sPrefConcurrentGCsMax != max_gcs_pref ||
sPrefConcurrentGCsCPUDivisor != cpu_divisor_pref) {
// We execute this if these preferences have changed. We also want to make
// sure it executes for the first IdleSchedulerParent, which it does because
// sPrefConcurrentGCsMax and sPrefConcurrentGCsCPUDivisor are initially
// zero.
sPrefConcurrentGCsMax = max_gcs_pref;
sPrefConcurrentGCsCPUDivisor = cpu_divisor_pref;
CalculateNumIdleTasks();
}
}
void IdleSchedulerParent::CalculateNumIdleTasks() {
MOZ_ASSERT(sNumCPUs);
MOZ_ASSERT(sPrefConcurrentGCsMax);
MOZ_ASSERT(sPrefConcurrentGCsCPUDivisor);
// On one and two processor (or hardware thread) systems this will
// allow one concurrent idle task.
sMaxConcurrentIdleTasksInChildProcesses = int32_t(std::max(sNumCPUs, 1u));
sMaxConcurrentGCs = std::clamp(sNumCPUs / sPrefConcurrentGCsCPUDivisor, 1u,
sPrefConcurrentGCsMax);
if (sActiveChildCounter && sActiveChildCounter->Memory()) {
static_cast<Atomic<int32_t>*>(
sActiveChildCounter->Memory())[NS_IDLE_SCHEDULER_INDEX_OF_CPU_COUNTER] =
static_cast<int32_t>(sMaxConcurrentIdleTasksInChildProcesses);
}
IdleSchedulerParent::Schedule(nullptr);
}
IdleSchedulerParent::~IdleSchedulerParent() {
// We can't know if an active process just crashed, so we just always expect
// that is the case.
if (mChildId) {
sInUseChildCounters[mChildId] = false;
if (sActiveChildCounter && sActiveChildCounter->Memory() &&
static_cast<Atomic<int32_t>*>(
sActiveChildCounter->Memory())[mChildId]) {
--static_cast<Atomic<int32_t>*>(
sActiveChildCounter
->Memory())[NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER];
static_cast<Atomic<int32_t>*>(sActiveChildCounter->Memory())[mChildId] =
0;
}
}
if (mRunningPrioritizedOperation) {
--sChildProcessesRunningPrioritizedOperation;
}
if (mDoingGC) {
// Give back our GC token.
sActiveGCs--;
}
if (mRequestingGC) {
mRequestingGC.value()(false);
mRequestingGC = Nothing();
}
// Remove from the scheduler's queue.
if (isInList()) {
remove();
}
MOZ_ASSERT(sChildProcessesAlive > 0);
sChildProcessesAlive--;
if (sChildProcessesAlive == 0) {
MOZ_ASSERT(sIdleAndGCRequests.isEmpty());
sActiveChildCounter = nullptr;
if (sStarvationPreventer) {
sStarvationPreventer->Cancel();
NS_RELEASE(sStarvationPreventer);
}
}
Schedule(nullptr);
}
IPCResult IdleSchedulerParent::RecvInitForIdleUse(
InitForIdleUseResolver&& aResolve) {
// This must already be non-zero, if it is zero then the cleanup code for the
// shared memory (initialised below) will never run. The invariant is that if
// the shared memory is initialsed, then this is non-zero.
MOZ_ASSERT(sChildProcessesAlive > 0);
MOZ_ASSERT(IsNotDoingIdleTask());
// Create a shared memory object which is shared across all the relevant
// processes.
if (!sActiveChildCounter) {
sActiveChildCounter = MakeRefPtr<SharedMemory>();
size_t shmemSize = NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT * sizeof(int32_t);
if (sActiveChildCounter->Create(shmemSize) &&
sActiveChildCounter->Map(shmemSize)) {
memset(sActiveChildCounter->Memory(), 0, shmemSize);
sInUseChildCounters[NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER] = true;
sInUseChildCounters[NS_IDLE_SCHEDULER_INDEX_OF_CPU_COUNTER] = true;
static_cast<Atomic<int32_t>*>(
sActiveChildCounter
->Memory())[NS_IDLE_SCHEDULER_INDEX_OF_CPU_COUNTER] =
static_cast<int32_t>(sMaxConcurrentIdleTasksInChildProcesses);
} else {
sActiveChildCounter = nullptr;
}
}
Maybe<SharedMemory::Handle> activeCounter;
if (SharedMemory::Handle handle =
sActiveChildCounter ? sActiveChildCounter->CloneHandle() : nullptr) {
activeCounter.emplace(std::move(handle));
}
uint32_t unusedId = 0;
for (uint32_t i = 0; i < NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT; ++i) {
if (!sInUseChildCounters[i]) {
sInUseChildCounters[i] = true;
unusedId = i;
break;
}
}
// If there wasn't an empty item, we'll fallback to 0.
mChildId = unusedId;
aResolve(std::tuple<mozilla::Maybe<SharedMemory::Handle>&&, const uint32_t&>(
std::move(activeCounter), mChildId));
return IPC_OK();
}
IPCResult IdleSchedulerParent::RecvRequestIdleTime(uint64_t aId,
TimeDuration aBudget) {
MOZ_ASSERT(aBudget);
MOZ_ASSERT(IsNotDoingIdleTask());
mCurrentRequestId = aId;
mRequestedIdleBudget = aBudget;
if (!isInList()) {
sIdleAndGCRequests.insertBack(this);
}
Schedule(this);
return IPC_OK();
}
IPCResult IdleSchedulerParent::RecvIdleTimeUsed(uint64_t aId) {
// The client can either signal that they've used the idle time or they're
// canceling the request. We cannot use a seperate cancel message because it
// could arrive after the parent has granted the request.
MOZ_ASSERT(IsWaitingForIdle() || IsDoingIdleTask());
// The parent process will always know the ID of the current request (since
// the IPC channel is reliable). The IDs are provided so that the client can
// check them (it's possible for the client to race ahead of the server).
MOZ_ASSERT(mCurrentRequestId == aId);
if (IsWaitingForIdle() && !mRequestingGC) {
remove();
}
mRequestedIdleBudget = TimeDuration();
Schedule(nullptr);
return IPC_OK();
}
IPCResult IdleSchedulerParent::RecvSchedule() {
Schedule(nullptr);
return IPC_OK();
}
IPCResult IdleSchedulerParent::RecvRunningPrioritizedOperation() {
++mRunningPrioritizedOperation;
if (mRunningPrioritizedOperation == 1) {
++sChildProcessesRunningPrioritizedOperation;
}
return IPC_OK();
}
IPCResult IdleSchedulerParent::RecvPrioritizedOperationDone() {
MOZ_ASSERT(mRunningPrioritizedOperation);
--mRunningPrioritizedOperation;
if (mRunningPrioritizedOperation == 0) {
--sChildProcessesRunningPrioritizedOperation;
Schedule(nullptr);
}
return IPC_OK();
}
IPCResult IdleSchedulerParent::RecvRequestGC(RequestGCResolver&& aResolver) {
MOZ_ASSERT(!mDoingGC);
MOZ_ASSERT(!mRequestingGC);
mRequestingGC = Some(aResolver);
if (!isInList()) {
sIdleAndGCRequests.insertBack(this);
}
Schedule(nullptr);
return IPC_OK();
}
IPCResult IdleSchedulerParent::RecvStartedGC() {
if (mDoingGC) {
return IPC_OK();
}
mDoingGC = true;
sActiveGCs++;
if (mRequestingGC) {
// We have to respond to the request before dropping it, even though the
// content process is already doing the GC.
mRequestingGC.value()(true);
mRequestingGC = Nothing();
if (!IsWaitingForIdle()) {
remove();
}
}
return IPC_OK();
}
IPCResult IdleSchedulerParent::RecvDoneGC() {
MOZ_ASSERT(mDoingGC);
sActiveGCs--;
mDoingGC = false;
Schedule(nullptr);
return IPC_OK();
}
int32_t IdleSchedulerParent::ActiveCount() {
if (sActiveChildCounter) {
return (static_cast<Atomic<int32_t>*>(
sActiveChildCounter
->Memory())[NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER]);
}
return 0;
}
bool IdleSchedulerParent::HasSpareCycles(int32_t aActiveCount) {
// We can run a new task if we have a spare core. If we're running a
// prioritised operation we halve the number of regular spare cores.
//
// sMaxConcurrentIdleTasksInChildProcesses will always be >0 so on 1 and 2
// core systems this will allow 1 idle tasks (0 if running a prioritized
// operation).
MOZ_ASSERT(sMaxConcurrentIdleTasksInChildProcesses > 0);
return sChildProcessesRunningPrioritizedOperation
? sMaxConcurrentIdleTasksInChildProcesses / 2 > aActiveCount
: sMaxConcurrentIdleTasksInChildProcesses > aActiveCount;
}
bool IdleSchedulerParent::HasSpareGCCycles() {
return sMaxConcurrentGCs > sActiveGCs;
}
void IdleSchedulerParent::SendIdleTime() {
// We would assert that IsWaitingForIdle() except after potentially removing
// the task from it's list this will return false. Instead check
// mRequestedIdleBudget.
MOZ_ASSERT(mRequestedIdleBudget);
Unused << SendIdleTime(mCurrentRequestId, mRequestedIdleBudget);
}
void IdleSchedulerParent::SendMayGC() {
MOZ_ASSERT(mRequestingGC);
mRequestingGC.value()(true);
mRequestingGC = Nothing();
mDoingGC = true;
sActiveGCs++;
}
void IdleSchedulerParent::Schedule(IdleSchedulerParent* aRequester) {
// Tasks won't update the active count until after they receive their message
// and start to run, so make a copy of it here and increment it for every task
// we schedule. It will become an estimate of how many tasks will be active
// shortly.
int32_t activeCount = ActiveCount();
if (aRequester && aRequester->mRunningPrioritizedOperation) {
// Prioritised operations are requested only for idle time requests, so this
// must be an idle time request.
MOZ_ASSERT(aRequester->IsWaitingForIdle());
// If the requester is prioritized, just let it run itself.
if (aRequester->isInList() && !aRequester->mRequestingGC) {
aRequester->remove();
}
aRequester->SendIdleTime();
activeCount++;
}
RefPtr<IdleSchedulerParent> idleRequester = sIdleAndGCRequests.getFirst();
bool has_spare_cycles = HasSpareCycles(activeCount);
bool has_spare_gc_cycles = HasSpareGCCycles();
while (idleRequester && (has_spare_cycles || has_spare_gc_cycles)) {
// Get the next element before potentially removing the current one from the
// list.
RefPtr<IdleSchedulerParent> next = idleRequester->getNext();
if (has_spare_cycles && idleRequester->IsWaitingForIdle()) {
// We can run an idle task.
activeCount++;
if (!idleRequester->mRequestingGC) {
idleRequester->remove();
}
idleRequester->SendIdleTime();
has_spare_cycles = HasSpareCycles(activeCount);
}
if (has_spare_gc_cycles && idleRequester->mRequestingGC) {
if (!idleRequester->IsWaitingForIdle()) {
idleRequester->remove();
}
idleRequester->SendMayGC();
has_spare_gc_cycles = HasSpareGCCycles();
}
idleRequester = next;
}
if (!sIdleAndGCRequests.isEmpty() && HasSpareCycles(activeCount)) {
EnsureStarvationTimer();
}
}
void IdleSchedulerParent::EnsureStarvationTimer() {
// Even though idle runnables aren't really guaranteed to get run ever (which
// is why most of them have the timer fallback), try to not let any child
// process' idle handling to starve forever in case other processes are busy
if (!sStarvationPreventer) {
// Reuse StaticPrefs::page_load_deprioritization_period(), since that
// is used on child side when deciding the minimum idle period.
NS_NewTimerWithFuncCallback(
&sStarvationPreventer, StarvationCallback, nullptr,
StaticPrefs::page_load_deprioritization_period(),
nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY, "StarvationCallback");
}
}
void IdleSchedulerParent::StarvationCallback(nsITimer* aTimer, void* aData) {
RefPtr<IdleSchedulerParent> idleRequester = sIdleAndGCRequests.getFirst();
while (idleRequester) {
if (idleRequester->IsWaitingForIdle()) {
// Treat the first process waiting for idle time as running prioritized
// operation so that it gets run.
++idleRequester->mRunningPrioritizedOperation;
++sChildProcessesRunningPrioritizedOperation;
Schedule(idleRequester);
--idleRequester->mRunningPrioritizedOperation;
--sChildProcessesRunningPrioritizedOperation;
break;
}
idleRequester = idleRequester->getNext();
}
NS_RELEASE(sStarvationPreventer);
}
} // namespace mozilla::ipc