Revert "Break deserializer reservations into chunks that fit onto a page."

src/serialize.cc

Index: src/serialize.cc
diff --git a/src/serialize.cc b/src/serialize.cc
index 4c9675e43f5275ac69d5446cabcc11905b5e3f0f..42ca6b9b228c1055f26f4e34e8ee84a000a62e80 100644
--- a/src/serialize.cc
+++ b/src/serialize.cc
@@ -598,7 +598,9 @@ Deserializer::Deserializer(SnapshotByteSource* source)
       source_(source),
       external_reference_decoder_(NULL),
       deserialized_large_objects_(0) {
-  for (int i = 0; i < kNumberOfPreallocatedSpaces; i++) current_chunk_[i] = 0;
+  for (int i = 0; i < kNumberOfSpaces; i++) {
+    reservations_[i] = kUninitializedReservation;
+  }
 }
 
 
@@ -611,19 +613,10 @@ void Deserializer::FlushICacheForNewCodeObjects() {
 }
 
 
-bool Deserializer::ReserveSpace() {
-  if (!isolate_->heap()->ReserveSpace(reservations_)) return false;
-  for (int i = 0; i < kNumberOfPreallocatedSpaces; i++) {
-    high_water_[i] = reservations_[i][0].start;
-  }
-  return true;
-}
-
-
 void Deserializer::Deserialize(Isolate* isolate) {
   isolate_ = isolate;
   DCHECK(isolate_ != NULL);
-  if (!ReserveSpace()) FatalProcessOutOfMemory("deserializing context");
+  isolate_->heap()->ReserveSpace(reservations_, high_water_);
   // No active threads.
   DCHECK_EQ(NULL, isolate_->thread_manager()->FirstThreadStateInUse());
   // No active handles.
@@ -665,17 +658,13 @@ void Deserializer::Deserialize(Isolate* isolate) {
 }
 
 
-void Deserializer::DeserializePartial(Isolate* isolate, Object** root,
-                                      OnOOM on_oom) {
+void Deserializer::DeserializePartial(Isolate* isolate, Object** root) {
   isolate_ = isolate;
   for (int i = NEW_SPACE; i < kNumberOfSpaces; i++) {
-    DCHECK(reservations_[i].length() > 0);
-  }
-  if (!ReserveSpace()) {
-    if (on_oom == FATAL_ON_OOM) FatalProcessOutOfMemory("deserialize context");
-    *root = NULL;
-    return;
+    DCHECK(reservations_[i] != kUninitializedReservation);
   }
+  Heap* heap = isolate->heap();
+  heap->ReserveSpace(reservations_, high_water_);
   if (external_reference_decoder_ == NULL) {
     external_reference_decoder_ = new ExternalReferenceDecoder(isolate);
   }
@@ -711,7 +700,7 @@ Deserializer::~Deserializer() {
 void Deserializer::VisitPointers(Object** start, Object** end) {
   // The space must be new space.  Any other space would cause ReadChunk to try
   // to update the remembered using NULL as the address.
-  ReadData(start, end, NEW_SPACE, NULL);
+  ReadChunk(start, end, NEW_SPACE, NULL);
 }
 
 
@@ -799,7 +788,7 @@ void Deserializer::ReadObject(int space_number,
   if (FLAG_log_snapshot_positions) {
     LOG(isolate_, SnapshotPositionEvent(address, source_->position()));
   }
-  ReadData(current, limit, space_number, address);
+  ReadChunk(current, limit, space_number, address);
 
   // TODO(mvstanton): consider treating the heap()->allocation_sites_list()
   // as a (weak) root. If this root is relocated correctly,
@@ -824,9 +813,6 @@ void Deserializer::ReadObject(int space_number,
 // pre-allocate that reserved space. During deserialization, all we need
 // to do is to bump up the pointer for each space in the reserved
 // space. This is also used for fixing back references.
-// We may have to split up the pre-allocation into several chunks
-// because it would not fit onto a single page, we have to keep track
-// of when to move to the next chunk.
 // Since multiple large objects cannot be folded into one large object
 // space allocation, we have to do an actual allocation when deserializing
 // each large object. Instead of tracking offset for back references, we
@@ -835,7 +821,7 @@ Address Deserializer::Allocate(int space_index, int size) {
   if (space_index == LO_SPACE) {
     AlwaysAllocateScope scope(isolate_);
     LargeObjectSpace* lo_space = isolate_->heap()->lo_space();
-    Executability exec = static_cast<Executability>(source_->Get());
+    Executability exec = static_cast<Executability>(source_->GetInt());
     AllocationResult result = lo_space->AllocateRaw(size, exec);
     HeapObject* obj = HeapObject::cast(result.ToObjectChecked());
     deserialized_large_objects_.Add(obj);
@@ -843,28 +829,16 @@ Address Deserializer::Allocate(int space_index, int size) {
   } else {
     DCHECK(space_index < kNumberOfPreallocatedSpaces);
     Address address = high_water_[space_index];
-    DCHECK_NE(NULL, address);
-    const Heap::Reservation& reservation = reservations_[space_index];
-    int chunk_index = current_chunk_[space_index];
-    if (address + size > reservation[chunk_index].end) {
-      // The last chunk size matches exactly the already deserialized data.
-      DCHECK_EQ(address, reservation[chunk_index].end);
-      // Move to next reserved chunk.
-      chunk_index = ++current_chunk_[space_index];
-      DCHECK_LT(chunk_index, reservation.length());
-      // Prepare for next allocation in the next chunk.
-      address = reservation[chunk_index].start;
-    } else {
-      high_water_[space_index] = address + size;
-    }
     high_water_[space_index] = address + size;
     return address;
   }
 }
 
 
-void Deserializer::ReadData(Object** current, Object** limit, int source_space,
-                            Address current_object_address) {
+void Deserializer::ReadChunk(Object** current,
+                             Object** limit,
+                             int source_space,
+                             Address current_object_address) {
   Isolate* const isolate = isolate_;
   // Write barrier support costs around 1% in startup time.  In fact there
   // are no new space objects in current boot snapshots, so it's not needed,
@@ -916,7 +890,7 @@ void Deserializer::ReadData(Object** current, Object** limit, int source_space,
         new_object = reinterpret_cast<Object*>(address);                       \
       } else if (where == kBackref) {                                          \
         emit_write_barrier = (space_number == NEW_SPACE);                      \
-        new_object = GetBackReferencedObject(data & kSpaceMask);               \
+        new_object = GetAddressFromEnd(data & kSpaceMask);                     \
         if (deserializing_user_code()) {                                       \
           new_object = ProcessBackRefInSerializedCode(new_object);             \
         }                                                                      \
@@ -939,7 +913,7 @@ void Deserializer::ReadData(Object** current, Object** limit, int source_space,
         current = reinterpret_cast<Object**>(                                  \
             reinterpret_cast<Address>(current) + skip);                        \
         emit_write_barrier = (space_number == NEW_SPACE);                      \
-        new_object = GetBackReferencedObject(data & kSpaceMask);               \
+        new_object = GetAddressFromEnd(data & kSpaceMask);                     \
         if (deserializing_user_code()) {                                       \
           new_object = ProcessBackRefInSerializedCode(new_object);             \
         }                                                                      \
@@ -1247,7 +1221,7 @@ Serializer::Serializer(Isolate* isolate, SnapshotByteSink* sink)
       seen_large_objects_index_(0) {
   // The serializer is meant to be used only to generate initial heap images
   // from a context in which there is only one isolate.
-  for (int i = 0; i < kNumberOfSpaces; i++) pending_chunk_[i] = 0;
+  for (int i = 0; i < kNumberOfSpaces; i++) fullness_[i] = 0;
 }
 
 
@@ -1309,19 +1283,6 @@ void Serializer::VisitPointers(Object** start, Object** end) {
 }
 
 
-void Serializer::FinalizeAllocation() {
-  DCHECK_EQ(0, completed_chunks_[LO_SPACE].length());  // Not yet finalized.
-  for (int i = 0; i < kNumberOfSpaces; i++) {
-    // Complete the last pending chunk and if there are no completed chunks,
-    // make sure there is at least one empty chunk.
-    if (pending_chunk_[i] > 0 || completed_chunks_[i].length() == 0) {
-      completed_chunks_[i].Add(pending_chunk_[i]);
-      pending_chunk_[i] = 0;
-    }
-  }
-}
-
-
 // This ensures that the partial snapshot cache keeps things alive during GC and
 // tracks their movement.  When it is called during serialization of the startup
 // snapshot nothing happens.  When the partial (context) snapshot is created,
@@ -1408,10 +1369,11 @@ void Serializer::SerializeReferenceToPreviousObject(HeapObject* heap_object,
     int index = address_mapper_.MappedTo(heap_object);
     sink_->PutInt(index, "large object index");
   } else {
-    uint32_t existing_allocation = address_mapper_.MappedTo(heap_object);
+    int address = address_mapper_.MappedTo(heap_object);
+    int offset = CurrentAllocationAddress(space) - address;
     // Shift out the bits that are always 0.
-    existing_allocation >>= kObjectAlignmentBits;
-    sink_->PutInt(existing_allocation, "allocation");
+    offset >>= kObjectAlignmentBits;
+    sink_->PutInt(offset, "offset");
   }
 }
 
@@ -1571,15 +1533,15 @@ void Serializer::ObjectSerializer::SerializePrologue(int space, int size,
   // Mark this object as already serialized.
   if (space == LO_SPACE) {
     if (object_->IsCode()) {
-      sink_->Put(EXECUTABLE, "executable large object");
+      sink_->PutInt(EXECUTABLE, "executable large object");
     } else {
-      sink_->Put(NOT_EXECUTABLE, "not executable large object");
+      sink_->PutInt(NOT_EXECUTABLE, "not executable large object");
     }
     int index = serializer_->AllocateLargeObject(size);
     serializer_->address_mapper()->AddMapping(object_, index);
   } else {
-    int allocation = serializer_->Allocate(space, size);
-    serializer_->address_mapper()->AddMapping(object_, allocation);
+    int offset = serializer_->Allocate(space, size);
+    serializer_->address_mapper()->AddMapping(object_, offset);
   }
 
   // Serialize the map (first word of the object).
@@ -1905,32 +1867,17 @@ int Serializer::SpaceOfObject(HeapObject* object) {
 }
 
 
-uint32_t Serializer::AllocateLargeObject(int size) {
-  // Large objects are allocated one-by-one when deserializing. We do not
-  // have to keep track of multiple chunks.
-  pending_chunk_[LO_SPACE] += size;
+int Serializer::AllocateLargeObject(int size) {
+  fullness_[LO_SPACE] += size;
   return seen_large_objects_index_++;
 }
 
 
-uint32_t Serializer::Allocate(int space, int size) {
+int Serializer::Allocate(int space, int size) {
   CHECK(space >= 0 && space < kNumberOfPreallocatedSpaces);
-  DCHECK(size > 0 && size < Page::kMaxRegularHeapObjectSize);
-  uint32_t new_chunk_size = pending_chunk_[space] + size;
-  uint32_t allocation;
-  if (new_chunk_size > Page::kMaxRegularHeapObjectSize) {
-    // The new chunk size would not fit onto a single page. Complete the
-    // current chunk and start a new one.
-    completed_chunks_[space].Add(pending_chunk_[space]);
-    pending_chunk_[space] = 0;
-    new_chunk_size = size;
-  }
-  // For back-referencing, each allocation is encoded as a combination
-  // of chunk index and offset inside the chunk.
-  allocation = ChunkIndexBits::encode(completed_chunks_[space].length()) |
-               OffsetBits::encode(pending_chunk_[space]);
-  pending_chunk_[space] = new_chunk_size;
-  return allocation;
+  int allocation_address = fullness_[space];
+  fullness_[space] = allocation_address + size;
+  return allocation_address;
 }
 
 
@@ -1976,7 +1923,6 @@ ScriptData* CodeSerializer::Serialize(Isolate* isolate,
   Object** location = Handle<Object>::cast(info).location();
   cs.VisitPointer(location);
   cs.Pad();
-  cs.FinalizeAllocation();
 
   SerializedCodeData data(&payload, &cs);
   ScriptData* script_data = data.GetScriptData();
@@ -2147,8 +2093,9 @@ void CodeSerializer::SerializeSourceObject(HowToCode how_to_code,
 }
 
 
-MaybeHandle<SharedFunctionInfo> CodeSerializer::Deserialize(
-    Isolate* isolate, ScriptData* data, Handle<String> source) {
+Handle<SharedFunctionInfo> CodeSerializer::Deserialize(Isolate* isolate,
+                                                       ScriptData* data,
+                                                       Handle<String> source) {
   base::ElapsedTimer timer;
   if (FLAG_profile_deserialization) timer.Start();
 
@@ -2160,15 +2107,10 @@ MaybeHandle<SharedFunctionInfo> CodeSerializer::Deserialize(
     SerializedCodeData scd(data, *source);
     SnapshotByteSource payload(scd.Payload(), scd.PayloadLength());
     Deserializer deserializer(&payload);
-
     STATIC_ASSERT(NEW_SPACE == 0);
-    int current_space = NEW_SPACE;
-    Vector<const SerializedCodeData::Reservation> res = scd.Reservations();
-    for (const auto& r : res) {
-      deserializer.AddReservation(current_space, r.chunk_size());
-      if (r.is_last_chunk()) current_space++;
+    for (int i = NEW_SPACE; i < kNumberOfSpaces; i++) {
+      deserializer.set_reservation(i, scd.GetReservation(i));
     }
-    DCHECK_EQ(kNumberOfSpaces, current_space);
 
     // Prepare and register list of attached objects.
     Vector<const uint32_t> code_stub_keys = scd.CodeStubKeys();
@@ -2182,12 +2124,7 @@ MaybeHandle<SharedFunctionInfo> CodeSerializer::Deserialize(
     deserializer.SetAttachedObjects(&attached_objects);
 
     // Deserialize.
-    deserializer.DeserializePartial(isolate, &root, Deserializer::NULL_ON_OOM);
-    if (root == NULL) {
-      // Deserializing may fail if the reservations cannot be fulfilled.
-      if (FLAG_profile_deserialization) PrintF("[Deserializing failed]\n");
-      return MaybeHandle<SharedFunctionInfo>();
-    }
+    deserializer.DeserializePartial(isolate, &root);
     deserializer.FlushICacheForNewCodeObjects();
   }
 
@@ -2207,25 +2144,10 @@ SerializedCodeData::SerializedCodeData(List<byte>* payload, CodeSerializer* cs)
   DisallowHeapAllocation no_gc;
   List<uint32_t>* stub_keys = cs->stub_keys();
 
-  // Gather reservation chunk sizes.
-  List<uint32_t> reservations(SerializerDeserializer::kNumberOfSpaces);
-  STATIC_ASSERT(NEW_SPACE == 0);
-  for (int i = 0; i < SerializerDeserializer::kNumberOfSpaces; i++) {
-    Vector<const uint32_t> chunks = cs->FinalAllocationChunks(i);
-    for (int j = 0; j < chunks.length(); j++) {
-      DCHECK(i == LO_SPACE || chunks[j] < Page::kMaxRegularHeapObjectSize);
-      uint32_t chunk = ChunkSizeBits::encode(chunks[j]) |
-                       IsLastChunkBits::encode(j == chunks.length() - 1);
-      reservations.Add(chunk);
-    }
-  }
-
   // Calculate sizes.
-  int reservation_size = reservations.length() * kInt32Size;
   int num_stub_keys = stub_keys->length();
   int stub_keys_size = stub_keys->length() * kInt32Size;
-  int data_length =
-      kHeaderSize + reservation_size + stub_keys_size + payload->length();
+  int data_length = kHeaderSize + stub_keys_size + payload->length();
 
   // Allocate backing store and create result data.
   byte* data = NewArray<byte>(data_length);
@@ -2235,21 +2157,20 @@ SerializedCodeData::SerializedCodeData(List<byte>* payload, CodeSerializer* cs)
 
   // Set header values.
   SetHeaderValue(kCheckSumOffset, CheckSum(cs->source()));
-  SetHeaderValue(kReservationsOffset, reservations.length());
   SetHeaderValue(kNumCodeStubKeysOffset, num_stub_keys);
   SetHeaderValue(kPayloadLengthOffset, payload->length());
-
-  // Copy reservation chunk sizes.
-  CopyBytes(data + kHeaderSize, reinterpret_cast<byte*>(reservations.begin()),
-            reservation_size);
+  STATIC_ASSERT(NEW_SPACE == 0);
+  for (int i = 0; i < SerializerDeserializer::kNumberOfSpaces; i++) {
+    SetHeaderValue(kReservationsOffset + i, cs->CurrentAllocationAddress(i));
+  }
 
   // Copy code stub keys.
-  CopyBytes(data + kHeaderSize + reservation_size,
-            reinterpret_cast<byte*>(stub_keys->begin()), stub_keys_size);
+  CopyBytes(data + kHeaderSize, reinterpret_cast<byte*>(stub_keys->begin()),
+            stub_keys_size);
 
   // Copy serialized data.
-  CopyBytes(data + kHeaderSize + reservation_size + stub_keys_size,
-            payload->begin(), static_cast<size_t>(payload->length()));
+  CopyBytes(data + kHeaderSize + stub_keys_size, payload->begin(),
+            static_cast<size_t>(payload->length()));
 }