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Gecko Idle detection relies heavily on RefreshDriver. GC/CC scheduling, including when to run GC or CC slices, and the length of the slices, is mostly based on idle time. As WebXR isn't using normal RefreshDriver, the content process thinks it's idle and GC and CC get basically up to 50 ms slices. Not having WebXR idle detection is causing stutter frames during immersive presentation. This patch implements idle deadline hint and sets the correct GC slices budgets during WebXR presentation. Differential Revision: https://phabricator.services.mozilla.com/D74426
76 lines
2.8 KiB
C++
76 lines
2.8 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 "mozilla/StaticPrefs_idle_period.h"
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#include "mozilla/dom/Document.h"
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#include "VRManagerChild.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 + idle_period.min + layout.idle_period.time_limit
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// or during page load
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// now + idle_period.during_page_load.min + layout.idle_period.time_limit
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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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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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if (XRE_IsContentProcess()) {
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currentGuess = gfx::VRManagerChild::GetIdleDeadlineHint(currentGuess);
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}
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currentGuess = NS_GetTimerDeadlineHintOnCurrentThread(currentGuess,
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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(StaticPrefs::idle_period_min());
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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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// During page load use higher minimum idle period.
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if (!busySoon && XRE_IsContentProcess() &&
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mozilla::dom::Document::HasRecentlyStartedForegroundLoads()) {
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TimeDuration minIdlePeriod = TimeDuration::FromMilliseconds(
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StaticPrefs::idle_period_during_page_load_min());
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busySoon = (now >= (currentGuess - minIdlePeriod));
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}
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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 */
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float MainThreadIdlePeriod::GetLongIdlePeriod() { return kLongIdlePeriodMS; }
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} // namespace mozilla
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