xpcom/threads/IdleTaskRunner.cpp
author Henri Sivonen <hsivonen@hsivonen.fi>
Fri, 06 Jul 2018 10:44:43 +0300
changeset 489140 4ef0f163fdeb9afeddd87b37bfd987298c038542
parent 479074 1d80ff31f25a7b113b51738590187b9b0acafa34
child 501569 7b36a8c21a150097364be7d4642904bc2051e93c
permissions -rw-r--r--
Bug 1402247 - Use encoding_rs for XPCOM string encoding conversions. r=Nika,erahm,froydnj. Correctness improvements: * UTF errors are handled safely per spec instead of dangerously truncating strings. * There are fewer converter implementations. Performance improvements: * The old code did exact buffer length math, which meant doing UTF math twice on each input string (once for length calculation and another time for conversion). Exact length math is more complicated when handling errors properly, which the old code didn't do. The new code does UTF math on the string content only once (when converting) but risks allocating more than once. There are heuristics in place to lower the probability of reallocation in cases where the double math avoidance isn't enough of a saving to absorb an allocation and memcpy. * Previously, in UTF-16 <-> UTF-8 conversions, an ASCII prefix was optimized but a single non-ASCII code point pessimized the rest of the string. The new code tries to get back on the fast ASCII path. * UTF-16 to Latin1 conversion guarantees less about handling of out-of-range input to eliminate an operation from the inner loop on x86/x86_64. * When assigning to a pre-existing string, the new code tries to reuse the old buffer instead of first releasing the old buffer and then allocating a new one. * When reallocating from the new code, the memcpy covers only the data that is part of the logical length of the old string instead of memcpying the whole capacity. (For old callers old excess memcpy behavior is preserved due to bogus callers. See bug 1472113.) * UTF-8 strings in XPConnect that are in the Latin1 range are passed to SpiderMonkey as Latin1. New features: * Conversion between UTF-8 and Latin1 is added in order to enable faster future interop between Rust code (or otherwise UTF-8-using code) and text node and SpiderMonkey code that uses Latin1. MozReview-Commit-ID: JaJuExfILM9

/* -*- 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
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "IdleTaskRunner.h"
#include "nsRefreshDriver.h"
#include "mozilla/SystemGroup.h"
#include "nsComponentManagerUtils.h"

namespace mozilla {

already_AddRefed<IdleTaskRunner>
IdleTaskRunner::Create(const CallbackType& aCallback,
                       const char* aRunnableName, uint32_t aDelay,
                       int64_t aBudget, bool aRepeating,
                       const MayStopProcessingCallbackType& aMayStopProcessing,
                       TaskCategory aTaskCategory)
{
  if (aMayStopProcessing && aMayStopProcessing()) {
    return nullptr;
  }

  RefPtr<IdleTaskRunner> runner =
    new IdleTaskRunner(aCallback, aRunnableName, aDelay,
                       aBudget, aRepeating, aMayStopProcessing,
                       aTaskCategory);
  runner->Schedule(false); // Initial scheduling shouldn't use idle dispatch.
  return runner.forget();
}

IdleTaskRunner::IdleTaskRunner(const CallbackType& aCallback,
                               const char* aRunnableName,
                               uint32_t aDelay, int64_t aBudget,
                               bool aRepeating,
                               const MayStopProcessingCallbackType& aMayStopProcessing,
                               TaskCategory aTaskCategory)
  : IdleRunnable(aRunnableName)
  , mCallback(aCallback), mDelay(aDelay)
  , mBudget(TimeDuration::FromMilliseconds(aBudget))
  , mRepeating(aRepeating), mTimerActive(false)
  , mMayStopProcessing(aMayStopProcessing)
  , mTaskCategory(aTaskCategory)
  , mName(aRunnableName)
{
}

NS_IMETHODIMP
IdleTaskRunner::Run()
{
  if (!mCallback) {
    return NS_OK;
  }

  // Deadline is null when called from timer.
  TimeStamp now = TimeStamp::Now();
  bool deadLineWasNull = mDeadline.IsNull();
  bool didRun = false;
  bool allowIdleDispatch = false;
  if (deadLineWasNull || ((now + mBudget) < mDeadline)) {
    CancelTimer();
    didRun = mCallback(mDeadline);
    // If we didn't do meaningful work, don't schedule using immediate
    // idle dispatch, since that could lead to a loop until the idle
    // period ends.
    allowIdleDispatch = didRun;
  } else if (now >= mDeadline) {
    allowIdleDispatch = true;
  }

  if (mCallback && (mRepeating || !didRun)) {
    Schedule(allowIdleDispatch);
  } else {
    mCallback = nullptr;
  }

  return NS_OK;
}

static void
TimedOut(nsITimer* aTimer, void* aClosure)
{
  RefPtr<IdleTaskRunner> runnable = static_cast<IdleTaskRunner*>(aClosure);
  runnable->Run();
}

void
IdleTaskRunner::SetDeadline(mozilla::TimeStamp aDeadline)
{
  mDeadline = aDeadline;
};

void IdleTaskRunner::SetTimer(uint32_t aDelay, nsIEventTarget* aTarget)
{
  MOZ_ASSERT(NS_IsMainThread());
  // aTarget is always the main thread event target provided from
  // NS_IdleDispatchToCurrentThread(). We ignore aTarget here to ensure that
  // CollectorRunner always run specifically on SystemGroup::EventTargetFor(
  // TaskCategory::GarbageCollection) of the main thread.
  SetTimerInternal(aDelay);
}

nsresult
IdleTaskRunner::Cancel()
{
  CancelTimer();
  mTimer = nullptr;
  mScheduleTimer = nullptr;
  mCallback = nullptr;
  return NS_OK;
}

static void
ScheduleTimedOut(nsITimer* aTimer, void* aClosure)
{
  RefPtr<IdleTaskRunner> runnable = static_cast<IdleTaskRunner*>(aClosure);
  runnable->Schedule(true);
}

void
IdleTaskRunner::Schedule(bool aAllowIdleDispatch)
{
  if (!mCallback) {
    return;
  }

  if (mMayStopProcessing && mMayStopProcessing()) {
    Cancel();
    return;
  }

  mDeadline = TimeStamp();
  TimeStamp now = TimeStamp::Now();
  TimeStamp hint = nsRefreshDriver::GetIdleDeadlineHint(now);
  if (hint != now) {
    // RefreshDriver is ticking, let it schedule the idle dispatch.
    nsRefreshDriver::DispatchIdleRunnableAfterTick(this, mDelay);
    // Ensure we get called at some point, even if RefreshDriver is stopped.
    SetTimerInternal(mDelay);
  } else {
    // RefreshDriver doesn't seem to be running.
    if (aAllowIdleDispatch) {
      nsCOMPtr<nsIRunnable> runnable = this;
      SetTimerInternal(mDelay);
      NS_IdleDispatchToCurrentThread(runnable.forget());
    } else {
      if (!mScheduleTimer) {
        mScheduleTimer = NS_NewTimer();
        if (!mScheduleTimer) {
          return;
        }
      } else {
        mScheduleTimer->Cancel();
      }
      if (TaskCategory::Count != mTaskCategory) {
        mScheduleTimer->SetTarget(SystemGroup::EventTargetFor(mTaskCategory));
      }
      // We weren't allowed to do idle dispatch immediately, do it after a
      // short timeout.
      mScheduleTimer->InitWithNamedFuncCallback(ScheduleTimedOut, this, 16,
                                                nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY,
                                                mName);
    }
  }
}

IdleTaskRunner::~IdleTaskRunner()
{
  CancelTimer();
}

void
IdleTaskRunner::CancelTimer()
{
  nsRefreshDriver::CancelIdleRunnable(this);
  if (mTimer) {
    mTimer->Cancel();
  }
  if (mScheduleTimer) {
    mScheduleTimer->Cancel();
  }
  mTimerActive = false;
}

void
IdleTaskRunner::SetTimerInternal(uint32_t aDelay)
{
  if (mTimerActive) {
    return;
  }

  if (!mTimer) {
    mTimer = NS_NewTimer();
  } else {
    mTimer->Cancel();
  }

  if (mTimer) {
    if (TaskCategory::Count != mTaskCategory) {
      mTimer->SetTarget(SystemGroup::EventTargetFor(mTaskCategory));
    }
    mTimer->InitWithNamedFuncCallback(TimedOut, this, aDelay,
                                      nsITimer::TYPE_ONE_SHOT,
                                      mName);
    mTimerActive = true;
  }
}

} // end of namespace mozilla