third_party/WebKit/Source/core/html/parser/HTMLParserScheduler.cpp

   1 /*
   2  * Copyright (C) 2010 Google, Inc. All Rights Reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "config.h"
  27 #include "core/html/parser/HTMLParserScheduler.h"
  28
  29 #include "core/dom/Document.h"
  30 #include "core/html/parser/HTMLDocumentParser.h"
  31 #include "core/frame/FrameView.h"
  32 #include "public/platform/Platform.h"
  33 #include "public/platform/WebScheduler.h"
  34 #include "public/platform/WebThread.h"
  35 #include "wtf/CurrentTime.h"
  36
  37 namespace blink {
  38
  39 ActiveParserSession::ActiveParserSession(unsigned& nestingLevel, Document* document)
  40     : NestingLevelIncrementer(nestingLevel)
  41     , m_document(document)
  42 {
  43     if (!m_document)
  44         return;
  45     m_document->incrementActiveParserCount();
  46 }
  47
  48 ActiveParserSession::~ActiveParserSession()
  49 {
  50     if (!m_document)
  51         return;
  52     m_document->decrementActiveParserCount();
  53 }
  54
  55 PumpSession::PumpSession(unsigned& nestingLevel, Document* document)
  56     : ActiveParserSession(nestingLevel, document)
  57 {
  58 }
  59
  60 PumpSession::~PumpSession()
  61 {
  62 }
  63
  64 SpeculationsPumpSession::SpeculationsPumpSession(unsigned& nestingLevel, Document* document)
  65     : ActiveParserSession(nestingLevel, document)
  66     , m_startTime(currentTime())
  67     , m_processedElementTokens(0)
  68 {
  69 }
  70
  71 SpeculationsPumpSession::~SpeculationsPumpSession()
  72 {
  73 }
  74
  75 inline double SpeculationsPumpSession::elapsedTime() const
  76 {
  77     return currentTime() - m_startTime;
  78 }
  79
  80 void SpeculationsPumpSession::addedElementTokens(size_t count)
  81 {
  82     m_processedElementTokens += count;
  83 }
  84
  85 HTMLParserScheduler::HTMLParserScheduler(HTMLDocumentParser* parser)
  86     : m_parser(parser)
  87     , m_loadingTaskRunner(Platform::current()->currentThread()->scheduler()->loadingTaskRunner())
  88     , m_cancellableContinueParse(CancellableTaskFactory::create(this, &HTMLParserScheduler::continueParsing))
  89     , m_isSuspendedWithActiveTimer(false)
  90 {
  91 }
  92
  93 HTMLParserScheduler::~HTMLParserScheduler()
  94 {
  95 }
  96
  97 void HTMLParserScheduler::scheduleForResume()
  98 {
  99     ASSERT(!m_isSuspendedWithActiveTimer);
 100     m_loadingTaskRunner->postTask(FROM_HERE, m_cancellableContinueParse->cancelAndCreate());
 101 }
 102
 103 void HTMLParserScheduler::suspend()
 104 {
 105     ASSERT(!m_isSuspendedWithActiveTimer);
 106     if (!m_cancellableContinueParse->isPending())
 107         return;
 108     m_isSuspendedWithActiveTimer = true;
 109     m_cancellableContinueParse->cancel();
 110 }
 111
 112 void HTMLParserScheduler::resume()
 113 {
 114     ASSERT(!m_cancellableContinueParse->isPending());
 115     if (!m_isSuspendedWithActiveTimer)
 116         return;
 117     m_isSuspendedWithActiveTimer = false;
 118
 119     m_loadingTaskRunner->postTask(FROM_HERE, m_cancellableContinueParse->cancelAndCreate());
 120 }
 121
 122 void HTMLParserScheduler::detach()
 123 {
 124     m_cancellableContinueParse->cancel();
 125     m_isSuspendedWithActiveTimer = false;
 126 }
 127
 128 inline bool HTMLParserScheduler::shouldYield(const SpeculationsPumpSession& session, bool startingScript) const
 129 {
 130     if (Platform::current()->currentThread()->scheduler()->shouldYieldForHighPriorityWork())
 131         return true;
 132
 133     const double parserTimeLimit = 0.5;
 134     if (session.elapsedTime() > parserTimeLimit)
 135         return true;
 136
 137     // Yield if a lot of DOM work has been done in this session and a script tag is
 138     // about to be parsed. This significantly improves render performance for documents
 139     // that place their scripts at the bottom of the page. Yielding too often
 140     // significantly slows down the parsing so a balance needs to be struck to
 141     // only yield when enough changes have happened to make it worthwhile.
 142     // Emperical testing shows that anything > ~40 and < ~200 gives all of the benefit
 143     // without impacting parser performance, only adding a few yields per page but at
 144     // just the right times.
 145     const size_t sufficientWork = 50;
 146     if (startingScript && session.processedElementTokens() > sufficientWork)
 147         return true;
 148
 149     return false;
 150 }
 151
 152 bool HTMLParserScheduler::yieldIfNeeded(const SpeculationsPumpSession& session, bool startingScript)
 153 {
 154     if (shouldYield(session, startingScript)) {
 155         scheduleForResume();
 156         return true;
 157     }
 158
 159     return false;
 160 }
 161
 162 void HTMLParserScheduler::forceResumeAfterYield()
 163 {
 164     ASSERT(!m_cancellableContinueParse->isPending());
 165     m_isSuspendedWithActiveTimer = true;
 166 }
 167
 168 void HTMLParserScheduler::continueParsing()
 169 {
 170     m_parser->resumeParsingAfterYield();
 171 }
 172
 173 }