Revert of Simple BlinkGC heap compaction.

third_party/WebKit/Source/platform/heap/HeapCompact.cpp

Index: third_party/WebKit/Source/platform/heap/HeapCompact.cpp
diff --git a/third_party/WebKit/Source/platform/heap/HeapCompact.cpp b/third_party/WebKit/Source/platform/heap/HeapCompact.cpp
deleted file mode 100644
index 43f2d2283ef72598229a152879bd69bbc001aa69..0000000000000000000000000000000000000000
--- a/third_party/WebKit/Source/platform/heap/HeapCompact.cpp
+++ /dev/null
@@ -1,479 +0,0 @@
-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "platform/heap/HeapCompact.h"
-
-#include "platform/RuntimeEnabledFeatures.h"
-#include "platform/heap/Heap.h"
-#include "platform/heap/SparseHeapBitmap.h"
-#include "wtf/CurrentTime.h"
-#include "wtf/HashMap.h"
-#include "wtf/HashSet.h"
-#include "wtf/Vector.h"
-
-namespace blink {
-
-bool HeapCompact::s_forceCompactionGC = false;
-
-// The real worker behind heap compaction, recording references to movable
-// objects ("slots".) When the objects end up being compacted and moved,
-// relocate() will adjust the slots to point to the new location of the
-// object along with handling fixups for interior pointers.
-//
-// The "fixups" object is created and maintained for the lifetime of one
-// heap compaction-enhanced GC.
-class HeapCompact::MovableObjectFixups final {
- public:
-  static std::unique_ptr<MovableObjectFixups> create() {
-    return WTF::wrapUnique(new MovableObjectFixups);
-  }
-
-  ~MovableObjectFixups() {}
-
-  // For the arenas being compacted, record all pages belonging to them.
-  // This is needed to handle 'interior slots', pointers that themselves
-  // can move (independently from the reference the slot points to.)
-  void addCompactingPage(BasePage* page) {
-    DCHECK(!page->isLargeObjectPage());
-    m_relocatablePages.add(page);
-  }
-
-  void addInteriorFixup(MovableReference* slot) {
-    auto it = m_interiorFixups.find(slot);
-    // Ephemeron fixpoint iterations may cause repeated registrations.
-    if (UNLIKELY(it != m_interiorFixups.end())) {
-      DCHECK(!it->value);
-      return;
-    }
-    m_interiorFixups.add(slot, nullptr);
-    LOG_HEAP_COMPACTION("Interior slot: %p\n", slot);
-    Address slotAddress = reinterpret_cast<Address>(slot);
-    if (!m_interiors) {
-      m_interiors = SparseHeapBitmap::create(slotAddress);
-      return;
-    }
-    m_interiors->add(slotAddress);
-  }
-
-  void add(MovableReference* slot) {
-    MovableReference reference = *slot;
-    BasePage* refPage = pageFromObject(reference);
-    // Nothing to compact on a large object's page.
-    if (refPage->isLargeObjectPage())
-      return;
-
-#if DCHECK_IS_ON()
-    DCHECK(HeapCompact::isCompactableArena(refPage->arena()->arenaIndex()));
-    auto it = m_fixups.find(reference);
-    DCHECK(it == m_fixups.end() || it->value == slot);
-#endif
-
-    // TODO: when updateHeapResidency() becomes more discriminating about
-    // leaving out arenas that aren't worth compacting, a check for
-    // isCompactingArena() would be appropriate here, leaving early if
-    // |refPage|'s arena isn't in the set.
-
-    m_fixups.add(reference, slot);
-
-    // Note: |slot| will reside outside the Oilpan heap if it is a
-    // PersistentHeapCollectionBase. Hence pageFromObject() cannot be
-    // used, as it sanity checks the |BasePage| it returns. Simply
-    // derive the raw BasePage address here and check if it is a member
-    // of the compactable and relocatable page address set.
-    Address slotAddress = reinterpret_cast<Address>(slot);
-    BasePage* slotPage = reinterpret_cast<BasePage*>(
-        blinkPageAddress(slotAddress) + blinkGuardPageSize);
-    if (LIKELY(!m_relocatablePages.contains(slotPage)))
-      return;
-#if ENABLE(ASSERT)
-    slotPage->contains(slotAddress);
-#endif
-    // Unlikely case, the slot resides on a compacting arena's page.
-    //  => It is an 'interior slot' (interior to a movable backing store.)
-    // Record it as an interior slot, which entails:
-    //
-    //  - Storing it in the interior map, which maps the slot to
-    //    its (eventual) location. Initially nullptr.
-    //  - Mark it as being interior pointer within the page's
-    //    "interior" bitmap. This bitmap is used when moving a backing
-    //    store, quickly/ier checking if interior slots will have to
-    //    be additionally redirected.
-    addInteriorFixup(slot);
-  }
-
-  void addFixupCallback(MovableReference reference,
-                        MovingObjectCallback callback,
-                        void* callbackData) {
-    DCHECK(!m_fixupCallbacks.contains(reference));
-    m_fixupCallbacks.add(reference, std::pair<void*, MovingObjectCallback>(
-                                        callbackData, callback));
-  }
-
-  void relocateInteriorFixups(Address from, Address to, size_t size) {
-    SparseHeapBitmap* range = m_interiors->hasRange(from, size);
-    if (LIKELY(!range))
-      return;
-
-    // Scan through the payload, looking for interior pointer slots
-    // to adjust. If the backing store of such an interior slot hasn't
-    // been moved already, update the slot -> real location mapping.
-    // When the backing store is eventually moved, it'll use that location.
-    //
-    for (size_t offset = 0; offset < size; offset += sizeof(void*)) {
-      if (!range->isSet(from + offset))
-        continue;
-      MovableReference* slot =
-          reinterpret_cast<MovableReference*>(from + offset);
-      auto it = m_interiorFixups.find(slot);
-      if (it == m_interiorFixups.end())
-        continue;
-
-      // TODO: with the right sparse bitmap representation, it could be possible
-      // to quickly determine if we've now stepped past the last address
-      // that needed fixup in [address, address + size). Breaking out of this
-      // loop might be worth doing for hash table backing stores with a very
-      // low load factor. But interior fixups are rare.
-
-      // If |slot|'s mapping is set, then the slot has been adjusted already.
-      if (it->value)
-        continue;
-      Address fixup = to + offset;
-      LOG_HEAP_COMPACTION("Range interior fixup: %p %p %p\n", from + offset,
-                          it->value, fixup);
-      // Fill in the relocated location of the original slot at |slot|.
-      // when the backing store corresponding to |slot| is eventually
-      // moved/compacted, it'll update |to + offset| with a pointer to the
-      // moved backing store.
-      m_interiorFixups.set(slot, fixup);
-    }
-  }
-
-  void relocate(Address from, Address to) {
-    auto it = m_fixups.find(from);
-    DCHECK(it != m_fixups.end());
-#if DCHECK_IS_ON()
-    BasePage* fromPage = pageFromObject(from);
-    DCHECK(m_relocatablePages.contains(fromPage));
-#endif
-    MovableReference* slot = reinterpret_cast<MovableReference*>(it->value);
-    auto interior = m_interiorFixups.find(slot);
-    if (interior != m_interiorFixups.end()) {
-      MovableReference* slotLocation =
-          reinterpret_cast<MovableReference*>(interior->value);
-      if (!slotLocation) {
-        m_interiorFixups.set(slot, to);
-      } else {
-        LOG_HEAP_COMPACTION("Redirected slot: %p => %p\n", slot, slotLocation);
-        slot = slotLocation;
-      }
-    }
-    // If the slot has subsequently been updated, a prefinalizer or
-    // a destructor having mutated and expanded/shrunk the collection,
-    // do not update and relocate the slot -- |from| is no longer valid
-    // and referenced.
-    //
-    // The slot's contents may also have been cleared during weak processing;
-    // no work to be done in that case either.
-    if (UNLIKELY(*slot != from)) {
-      LOG_HEAP_COMPACTION(
-          "No relocation: slot = %p, *slot = %p, from = %p, to = %p\n", slot,
-          *slot, from, to);
-#if DCHECK_IS_ON()
-      // Verify that the already updated slot is valid, meaning:
-      //  - has been cleared.
-      //  - has been updated & expanded with a large object backing store.
-      //  - has been updated with a larger, freshly allocated backing store.
-      //    (on a fresh page in a compactable arena that is not being
-      //    compacted.)
-      if (!*slot)
-        return;
-      BasePage* slotPage = pageFromObject(*slot);
-      DCHECK(
-          slotPage->isLargeObjectPage() ||
-          (HeapCompact::isCompactableArena(slotPage->arena()->arenaIndex()) &&
-           !m_relocatablePages.contains(slotPage)));
-#endif
-      return;
-    }
-    *slot = to;
-
-    size_t size = 0;
-    auto callback = m_fixupCallbacks.find(from);
-    if (UNLIKELY(callback != m_fixupCallbacks.end())) {
-      size = HeapObjectHeader::fromPayload(to)->payloadSize();
-      callback->value.second(callback->value.first, from, to, size);
-    }
-
-    if (!m_interiors)
-      return;
-
-    if (!size)
-      size = HeapObjectHeader::fromPayload(to)->payloadSize();
-    relocateInteriorFixups(from, to, size);
-  }
-
-#if DEBUG_HEAP_COMPACTION
-  void dumpDebugStats() {
-    LOG_HEAP_COMPACTION(
-        "Fixups: pages=%u objects=%u callbacks=%u interior-size=%zu"
-        " interiors-f=%u\n",
-        m_relocatablePages.size(), m_fixups.size(), m_fixupCallbacks.size(),
-        m_interiors ? m_interiors->intervalCount() : 0,
-        m_interiorFixups.size());
-  }
-#endif
-
- private:
-  MovableObjectFixups() {}
-
-  // Tracking movable and updatable references. For now, we keep a
-  // map which for each movable object, recording the slot that
-  // points to it. Upon moving the object, that slot needs to be
-  // updated.
-  //
-  // (TODO: consider in-place updating schemes.)
-  HashMap<MovableReference, MovableReference*> m_fixups;
-
-  // Map from movable reference to callbacks that need to be invoked
-  // when the object moves.
-  HashMap<MovableReference, std::pair<void*, MovingObjectCallback>>
-      m_fixupCallbacks;
-
-  // Slot => relocated slot/final location.
-  HashMap<MovableReference*, Address> m_interiorFixups;
-
-  // All pages that are being compacted.
-  HashSet<BasePage*> m_relocatablePages;
-
-  std::unique_ptr<SparseHeapBitmap> m_interiors;
-};
-
-HeapCompact::HeapCompact()
-    : m_doCompact(false),
-      m_gcCountSinceLastCompaction(0),
-      m_threadCount(0),
-      m_freeListSize(0),
-      m_compactableArenas(0u),
-      m_freedPages(0),
-      m_freedSize(0)
-#if DEBUG_LOG_HEAP_COMPACTION_RUNNING_TIME
-      ,
-      m_startCompactionTimeMS(0)
-#endif
-{
-  // The heap compaction implementation assumes the contiguous range,
-  //
-  //   [Vector1ArenaIndex, HashTableArenaIndex]
-  //
-  // in a few places. Use static asserts here to not have that assumption
-  // be silently invalidated by ArenaIndices changes.
-  static_assert(BlinkGC::Vector1ArenaIndex + 3 == BlinkGC::Vector4ArenaIndex,
-                "unexpected ArenaIndices ordering");
-  static_assert(
-      BlinkGC::Vector4ArenaIndex + 1 == BlinkGC::InlineVectorArenaIndex,
-      "unexpected ArenaIndices ordering");
-  static_assert(
-      BlinkGC::InlineVectorArenaIndex + 1 == BlinkGC::HashTableArenaIndex,
-      "unexpected ArenaIndices ordering");
-}
-
-HeapCompact::~HeapCompact() {}
-
-HeapCompact::MovableObjectFixups& HeapCompact::fixups() {
-  if (!m_fixups)
-    m_fixups = MovableObjectFixups::create();
-  return *m_fixups;
-}
-
-bool HeapCompact::shouldCompact(ThreadState* state,
-                                BlinkGC::GCType gcType,
-                                BlinkGC::GCReason reason) {
-#if !ENABLE_HEAP_COMPACTION
-  return false;
-#else
-  if (!RuntimeEnabledFeatures::heapCompactionEnabled())
-    return false;
-
-  LOG_HEAP_COMPACTION("shouldCompact(): gc=%s count=%zu free=%zu\n",
-                      ThreadState::gcReasonString(reason),
-                      m_gcCountSinceLastCompaction, m_freeListSize);
-  m_gcCountSinceLastCompaction++;
-  // It is only safe to compact during non-conservative GCs.
-  // TODO: for the main thread, limit this further to only idle GCs.
-  if (reason != BlinkGC::IdleGC && reason != BlinkGC::PreciseGC &&
-      reason != BlinkGC::ForcedGC)
-    return false;
-
-  const ThreadHeap& heap = state->heap();
-  // If any of the participating threads require a stack scan,
-  // do not compact.
-  //
-  // Why? Should the stack contain an iterator pointing into its
-  // associated backing store, its references wouldn't be
-  // correctly relocated.
-  for (ThreadState* state : heap.threads()) {
-    if (state->stackState() == BlinkGC::HeapPointersOnStack) {
-      return false;
-    }
-  }
-
-  // Compaction enable rules:
-  //  - It's been a while since the last time.
-  //  - "Considerable" amount of heap memory is bound up in freelist
-  //    allocations. For now, use a fixed limit irrespective of heap
-  //    size.
-  //
-  // As this isn't compacting all arenas, the cost of doing compaction
-  // isn't a worry as it will additionally only be done by idle GCs.
-  // TODO: add some form of compaction overhead estimate to the marking
-  // time estimate.
-
-  updateHeapResidency(state);
-
-#if STRESS_TEST_HEAP_COMPACTION
-  // Exercise the handling of object movement by compacting as
-  // often as possible.
-  return true;
-#else
-  return s_forceCompactionGC ||
-         (m_gcCountSinceLastCompaction > kGCCountSinceLastCompactionThreshold &&
-          m_freeListSize > kFreeListSizeThreshold);
-#endif
-#endif
-}
-
-BlinkGC::GCType HeapCompact::initialize(ThreadState* state) {
-  DCHECK(RuntimeEnabledFeatures::heapCompactionEnabled());
-  LOG_HEAP_COMPACTION("Compacting: free=%zu\n", m_freeListSize);
-  m_doCompact = true;
-  m_freedPages = 0;
-  m_freedSize = 0;
-  m_threadCount = state->heap().threads().size();
-  m_fixups.reset();
-  m_gcCountSinceLastCompaction = 0;
-  s_forceCompactionGC = false;
-  return BlinkGC::GCWithSweepCompaction;
-}
-
-void HeapCompact::registerMovingObjectReference(MovableReference* slot) {
-  if (!m_doCompact)
-    return;
-
-  fixups().add(slot);
-}
-
-void HeapCompact::registerMovingObjectCallback(MovableReference reference,
-                                               MovingObjectCallback callback,
-                                               void* callbackData) {
-  if (!m_doCompact)
-    return;
-
-  fixups().addFixupCallback(reference, callback, callbackData);
-}
-
-void HeapCompact::updateHeapResidency(ThreadState* threadState) {
-  size_t totalArenaSize = 0;
-  size_t totalFreeListSize = 0;
-
-  m_compactableArenas = 0;
-#if DEBUG_HEAP_FREELIST
-  LOG_HEAP_FREELIST("Arena residencies: {");
-#endif
-  for (int i = BlinkGC::Vector1ArenaIndex; i <= BlinkGC::HashTableArenaIndex;
-       ++i) {
-    NormalPageArena* arena =
-        static_cast<NormalPageArena*>(threadState->arena(i));
-    size_t arenaSize = arena->arenaSize();
-    size_t freeListSize = arena->freeListSize();
-    totalArenaSize += arenaSize;
-    totalFreeListSize += freeListSize;
-    LOG_HEAP_FREELIST("%d: [%zu, %zu], ", i, arenaSize, freeListSize);
-    // TODO: be more discriminating and consider arena
-    // load factor, effectiveness of past compactions etc.
-    if (!arenaSize)
-      continue;
-    // Mark the arena as compactable.
-    m_compactableArenas |= (0x1u << (BlinkGC::Vector1ArenaIndex + i));
-  }
-  LOG_HEAP_FREELIST("}\nTotal = %zu, Free = %zu\n", totalArenaSize,
-                    totalFreeListSize);
-
-  // TODO(sof): consider smoothing the reported sizes.
-  m_freeListSize = totalFreeListSize;
-}
-
-void HeapCompact::finishedArenaCompaction(NormalPageArena* arena,
-                                          size_t freedPages,
-                                          size_t freedSize) {
-  if (!m_doCompact)
-    return;
-
-  m_freedPages += freedPages;
-  m_freedSize += freedSize;
-}
-
-void HeapCompact::relocate(Address from, Address to) {
-  DCHECK(m_fixups);
-  m_fixups->relocate(from, to);
-}
-
-void HeapCompact::startThreadCompaction() {
-  if (!m_doCompact)
-    return;
-#if DEBUG_LOG_HEAP_COMPACTION_RUNNING_TIME
-  MutexLocker locker(m_mutex);
-  if (!m_startCompactionTimeMS)
-    m_startCompactionTimeMS = WTF::currentTimeMS();
-#endif
-}
-
-void HeapCompact::finishThreadCompaction() {
-  if (!m_doCompact)
-    return;
-
-  MutexLocker locker(m_mutex);
-  // Final one clears out.
-  if (!--m_threadCount) {
-#if DEBUG_HEAP_COMPACTION
-    if (m_fixups)
-      m_fixups->dumpDebugStats();
-#endif
-    m_fixups.reset();
-    m_doCompact = false;
-#if DEBUG_LOG_HEAP_COMPACTION_RUNNING_TIME
-    double end = WTF::currentTimeMS();
-    LOG_HEAP_COMPACTION_INTERNAL(
-        "Compaction stats: time=%gms, pages freed=%zu, size=%zu\n",
-        end - m_startCompactionTimeMS, m_freedPages, m_freedSize);
-    m_startCompactionTimeMS = 0;
-#else
-    LOG_HEAP_COMPACTION("Compaction stats: freed pages=%zu size=%zu\n",
-                        m_freedPages, m_freedSize);
-#endif
-    // Compaction has been completed by all participating threads, unblock
-    // them all.
-    m_finished.broadcast();
-  } else {
-    // Letting a thread return here and let it exit its safe point opens up
-    // the possibility of it accessing heaps of other threads that are
-    // still being compacted. It is not in a valid state until objects have
-    // all been moved together, hence all GC-participating threads must
-    // complete compaction together. Grab the condition variable and wait.
-    m_finished.wait(m_mutex);
-  }
-}
-
-void HeapCompact::addCompactingPage(BasePage* page) {
-  DCHECK(m_doCompact);
-  DCHECK(isCompactingArena(page->arena()->arenaIndex()));
-  fixups().addCompactingPage(page);
-}
-
-bool HeapCompact::scheduleCompactionGCForTesting(bool value) {
-  bool current = s_forceCompactionGC;
-  s_forceCompactionGC = value;
-  return current;
-}
-
-}  // namespace blink