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79aa95fa24
There's no good reason why these can't be code constants.
Especially given that, due to a bug, changes to the
"idle_queue.{min,long}_period" constants were not being passed onto the C++
code!
Here's why: those two prefs were specified as integers in all.js. But we used
AddFloatVarCache() to set up the reading of those prefs. libpref fakes floats
by storing them as strings and then converting them to floats when they are
read.
Which means that AddFloatVarCache() used to fail to get the value from all.js
-- because there's a type mismatch, int vs. string -- and instead use the
fallback default. That value is the same as the one in all.js, which is lucky.
But if someone changed the value in about:config to 100 (an integer), a similar
failure would have occured and the value used by the C++ code wouldn't be
updated!
Also note that idle_queue.max_timer_thread_bound did not have a value in
all.js.
What a mess!
--HG--
extra : rebase_source : 86f8fa905163803eb95007609c029e18c2c4f586
64 lines
2.1 KiB
C++
64 lines
2.1 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "MainThreadIdlePeriod.h"
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#include "mozilla/Maybe.h"
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#include "mozilla/Preferences.h"
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#include "nsRefreshDriver.h"
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#include "nsThreadUtils.h"
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// The amount of idle time (milliseconds) reserved for a long idle period.
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static const double kLongIdlePeriodMS = 50.0;
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// The minimum amount of time (milliseconds) required for an idle period to be
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// scheduled on the main thread. N.B. layout.idle_period.time_limit adds
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// padding at the end of the idle period, which makes the point in time that we
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// expect to become busy again be:
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// now + kMinIdlePeriodMS + layout.idle_period.time_limit
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static const double kMinIdlePeriodMS = 3.0;
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static const uint32_t kMaxTimerThreadBound = 5; // milliseconds
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static const uint32_t kMaxTimerThreadBoundClamp = 15; // milliseconds
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namespace mozilla {
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NS_IMETHODIMP
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MainThreadIdlePeriod::GetIdlePeriodHint(TimeStamp* aIdleDeadline)
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{
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MOZ_ASSERT(NS_IsMainThread());
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MOZ_ASSERT(aIdleDeadline);
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TimeStamp now = TimeStamp::Now();
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TimeStamp currentGuess =
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now + TimeDuration::FromMilliseconds(kLongIdlePeriodMS);
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currentGuess = nsRefreshDriver::GetIdleDeadlineHint(currentGuess);
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currentGuess = NS_GetTimerDeadlineHintOnCurrentThread(currentGuess, kMaxTimerThreadBound);
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// If the idle period is too small, then just return a null time
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// to indicate we are busy. Otherwise return the actual deadline.
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TimeDuration minIdlePeriod =
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TimeDuration::FromMilliseconds(kMinIdlePeriodMS);
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bool busySoon = currentGuess.IsNull() ||
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(now >= (currentGuess - minIdlePeriod)) ||
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currentGuess < mLastIdleDeadline;
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if (!busySoon) {
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*aIdleDeadline = mLastIdleDeadline = currentGuess;
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}
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return NS_OK;
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}
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/* static */ float
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MainThreadIdlePeriod::GetLongIdlePeriod()
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{
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return kLongIdlePeriodMS;
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}
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} // namespace mozilla
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