Line data Source code
1 : // Copyright 2015 the V8 project authors. All rights reserved.
2 : // Use of this source code is governed by a BSD-style license that can be
3 : // found in the LICENSE file.
4 :
5 : #ifndef V8_HEAP_SCAVENGER_H_
6 : #define V8_HEAP_SCAVENGER_H_
7 :
8 : #include "src/base/platform/condition-variable.h"
9 : #include "src/heap/local-allocator.h"
10 : #include "src/heap/objects-visiting.h"
11 : #include "src/heap/slot-set.h"
12 : #include "src/heap/worklist.h"
13 :
14 : namespace v8 {
15 : namespace internal {
16 :
17 : class OneshotBarrier;
18 :
19 : enum class CopyAndForwardResult {
20 : SUCCESS_YOUNG_GENERATION,
21 : SUCCESS_OLD_GENERATION,
22 : FAILURE
23 : };
24 :
25 : using ObjectAndSize = std::pair<HeapObject, int>;
26 : using SurvivingNewLargeObjectsMap =
27 : std::unordered_map<HeapObject, Map, Object::Hasher>;
28 : using SurvivingNewLargeObjectMapEntry = std::pair<HeapObject, Map>;
29 :
30 : constexpr int kEphemeronTableListSegmentSize = 128;
31 : using EphemeronTableList =
32 : Worklist<EphemeronHashTable, kEphemeronTableListSegmentSize>;
33 :
34 61519 : class ScavengerCollector {
35 : public:
36 : static const int kMaxScavengerTasks = 8;
37 : static const int kMaxWaitTimeMs = 2;
38 :
39 : explicit ScavengerCollector(Heap* heap);
40 :
41 : void CollectGarbage();
42 :
43 : private:
44 : void MergeSurvivingNewLargeObjects(
45 : const SurvivingNewLargeObjectsMap& objects);
46 :
47 : int NumberOfScavengeTasks();
48 :
49 : void ProcessWeakReferences(EphemeronTableList* ephemeron_table_list);
50 : void ClearYoungEphemerons(EphemeronTableList* ephemeron_table_list);
51 : void HandleSurvivingNewLargeObjects();
52 :
53 : Isolate* const isolate_;
54 : Heap* const heap_;
55 : base::Semaphore parallel_scavenge_semaphore_;
56 : SurvivingNewLargeObjectsMap surviving_new_large_objects_;
57 :
58 : friend class Scavenger;
59 : };
60 :
61 101802 : class Scavenger {
62 : public:
63 : struct PromotionListEntry {
64 : HeapObject heap_object;
65 : Map map;
66 : int size;
67 : };
68 :
69 20973 : class PromotionList {
70 : public:
71 : class View {
72 : public:
73 : View(PromotionList* promotion_list, int task_id)
74 33934 : : promotion_list_(promotion_list), task_id_(task_id) {}
75 :
76 : inline void PushRegularObject(HeapObject object, int size);
77 : inline void PushLargeObject(HeapObject object, Map map, int size);
78 : inline bool IsEmpty();
79 : inline size_t LocalPushSegmentSize();
80 : inline bool Pop(struct PromotionListEntry* entry);
81 : inline bool IsGlobalPoolEmpty();
82 : inline bool ShouldEagerlyProcessPromotionList();
83 :
84 : private:
85 : PromotionList* promotion_list_;
86 : int task_id_;
87 : };
88 :
89 : explicit PromotionList(int num_tasks)
90 : : regular_object_promotion_list_(num_tasks),
91 20973 : large_object_promotion_list_(num_tasks) {}
92 :
93 : inline void PushRegularObject(int task_id, HeapObject object, int size);
94 : inline void PushLargeObject(int task_id, HeapObject object, Map map,
95 : int size);
96 : inline bool IsEmpty();
97 : inline size_t LocalPushSegmentSize(int task_id);
98 : inline bool Pop(int task_id, struct PromotionListEntry* entry);
99 : inline bool IsGlobalPoolEmpty();
100 : inline bool ShouldEagerlyProcessPromotionList(int task_id);
101 :
102 : private:
103 : static const int kRegularObjectPromotionListSegmentSize = 256;
104 : static const int kLargeObjectPromotionListSegmentSize = 4;
105 :
106 : using RegularObjectPromotionList =
107 : Worklist<ObjectAndSize, kRegularObjectPromotionListSegmentSize>;
108 : using LargeObjectPromotionList =
109 : Worklist<PromotionListEntry, kLargeObjectPromotionListSegmentSize>;
110 :
111 : RegularObjectPromotionList regular_object_promotion_list_;
112 : LargeObjectPromotionList large_object_promotion_list_;
113 : };
114 :
115 : static const int kCopiedListSegmentSize = 256;
116 :
117 : using CopiedList = Worklist<ObjectAndSize, kCopiedListSegmentSize>;
118 : Scavenger(ScavengerCollector* collector, Heap* heap, bool is_logging,
119 : CopiedList* copied_list, PromotionList* promotion_list,
120 : EphemeronTableList* ephemeron_table_list, int task_id);
121 :
122 : // Entry point for scavenging an old generation page. For scavenging single
123 : // objects see RootScavengingVisitor and ScavengeVisitor below.
124 : void ScavengePage(MemoryChunk* page);
125 :
126 : // Processes remaining work (=objects) after single objects have been
127 : // manually scavenged using ScavengeObject or CheckAndScavengeObject.
128 : void Process(OneshotBarrier* barrier = nullptr);
129 :
130 : // Finalize the Scavenger. Needs to be called from the main thread.
131 : void Finalize();
132 :
133 : void AddEphemeronHashTable(EphemeronHashTable table);
134 :
135 : size_t bytes_copied() const { return copied_size_; }
136 : size_t bytes_promoted() const { return promoted_size_; }
137 :
138 : private:
139 : // Number of objects to process before interrupting for potentially waking
140 : // up other tasks.
141 : static const int kInterruptThreshold = 128;
142 : static const int kInitialLocalPretenuringFeedbackCapacity = 256;
143 :
144 : inline Heap* heap() { return heap_; }
145 :
146 : inline void PageMemoryFence(MaybeObject object);
147 :
148 : void AddPageToSweeperIfNecessary(MemoryChunk* page);
149 :
150 : // Potentially scavenges an object referenced from |slot| if it is
151 : // indeed a HeapObject and resides in from space.
152 : template <typename TSlot>
153 : inline SlotCallbackResult CheckAndScavengeObject(Heap* heap, TSlot slot);
154 :
155 : // Scavenges an object |object| referenced from slot |p|. |object| is required
156 : // to be in from space.
157 : template <typename THeapObjectSlot>
158 : inline SlotCallbackResult ScavengeObject(THeapObjectSlot p,
159 : HeapObject object);
160 :
161 : // Copies |source| to |target| and sets the forwarding pointer in |source|.
162 : V8_INLINE bool MigrateObject(Map map, HeapObject source, HeapObject target,
163 : int size);
164 :
165 : V8_INLINE SlotCallbackResult
166 : RememberedSetEntryNeeded(CopyAndForwardResult result);
167 :
168 : template <typename THeapObjectSlot>
169 : V8_INLINE CopyAndForwardResult
170 : SemiSpaceCopyObject(Map map, THeapObjectSlot slot, HeapObject object,
171 : int object_size, ObjectFields object_fields);
172 :
173 : template <typename THeapObjectSlot>
174 : V8_INLINE CopyAndForwardResult PromoteObject(Map map, THeapObjectSlot slot,
175 : HeapObject object,
176 : int object_size,
177 : ObjectFields object_fields);
178 :
179 : template <typename THeapObjectSlot>
180 : V8_INLINE SlotCallbackResult EvacuateObject(THeapObjectSlot slot, Map map,
181 : HeapObject source);
182 :
183 : V8_INLINE bool HandleLargeObject(Map map, HeapObject object, int object_size,
184 : ObjectFields object_fields);
185 :
186 : // Different cases for object evacuation.
187 : template <typename THeapObjectSlot>
188 : V8_INLINE SlotCallbackResult
189 : EvacuateObjectDefault(Map map, THeapObjectSlot slot, HeapObject object,
190 : int object_size, ObjectFields object_fields);
191 :
192 : template <typename THeapObjectSlot>
193 : inline SlotCallbackResult EvacuateThinString(Map map, THeapObjectSlot slot,
194 : ThinString object,
195 : int object_size);
196 :
197 : template <typename THeapObjectSlot>
198 : inline SlotCallbackResult EvacuateShortcutCandidate(Map map,
199 : THeapObjectSlot slot,
200 : ConsString object,
201 : int object_size);
202 :
203 : void IterateAndScavengePromotedObject(HeapObject target, Map map, int size);
204 :
205 : ScavengerCollector* const collector_;
206 : Heap* const heap_;
207 : PromotionList::View promotion_list_;
208 : CopiedList::View copied_list_;
209 : EphemeronTableList::View ephemeron_table_list_;
210 : Heap::PretenuringFeedbackMap local_pretenuring_feedback_;
211 : size_t copied_size_;
212 : size_t promoted_size_;
213 : LocalAllocator allocator_;
214 : SurvivingNewLargeObjectsMap surviving_new_large_objects_;
215 : const bool is_logging_;
216 : const bool is_incremental_marking_;
217 : const bool is_compacting_;
218 :
219 : friend class IterateAndScavengePromotedObjectsVisitor;
220 : friend class RootScavengeVisitor;
221 : friend class ScavengeVisitor;
222 : };
223 :
224 : // Helper class for turning the scavenger into an object visitor that is also
225 : // filtering out non-HeapObjects and objects which do not reside in new space.
226 41946 : class RootScavengeVisitor final : public RootVisitor {
227 : public:
228 : explicit RootScavengeVisitor(Scavenger* scavenger);
229 :
230 : void VisitRootPointer(Root root, const char* description,
231 : FullObjectSlot p) final;
232 : void VisitRootPointers(Root root, const char* description,
233 : FullObjectSlot start, FullObjectSlot end) final;
234 :
235 : private:
236 : void ScavengePointer(FullObjectSlot p);
237 :
238 : Scavenger* const scavenger_;
239 : };
240 :
241 88613 : class ScavengeVisitor final : public NewSpaceVisitor<ScavengeVisitor> {
242 : public:
243 : explicit ScavengeVisitor(Scavenger* scavenger);
244 :
245 : V8_INLINE void VisitPointers(HeapObject host, ObjectSlot start,
246 : ObjectSlot end) final;
247 :
248 : V8_INLINE void VisitPointers(HeapObject host, MaybeObjectSlot start,
249 : MaybeObjectSlot end) final;
250 :
251 : V8_INLINE void VisitCodeTarget(Code host, RelocInfo* rinfo) final;
252 : V8_INLINE void VisitEmbeddedPointer(Code host, RelocInfo* rinfo) final;
253 : V8_INLINE int VisitEphemeronHashTable(Map map, EphemeronHashTable object);
254 :
255 : private:
256 : template <typename TSlot>
257 : V8_INLINE void VisitHeapObjectImpl(TSlot slot, HeapObject heap_object);
258 :
259 : template <typename TSlot>
260 : V8_INLINE void VisitPointersImpl(HeapObject host, TSlot start, TSlot end);
261 :
262 : Scavenger* const scavenger_;
263 : };
264 :
265 : } // namespace internal
266 : } // namespace v8
267 :
268 : #endif // V8_HEAP_SCAVENGER_H_
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