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_MEMORY_REDUCER_H_
6 : #define V8_HEAP_MEMORY_REDUCER_H_
7 :
8 : #include "include/v8-platform.h"
9 : #include "src/base/macros.h"
10 : #include "src/cancelable-task.h"
11 : #include "src/globals.h"
12 :
13 : namespace v8 {
14 : namespace internal {
15 :
16 : class Heap;
17 :
18 :
19 : // The goal of the MemoryReducer class is to detect transition of the mutator
20 : // from high allocation phase to low allocation phase and to collect potential
21 : // garbage created in the high allocation phase.
22 : //
23 : // The class implements an automaton with the following states and transitions.
24 : //
25 : // States:
26 : // - DONE <last_gc_time_ms>
27 : // - WAIT <started_gcs> <next_gc_start_ms> <last_gc_time_ms>
28 : // - RUN <started_gcs> <last_gc_time_ms>
29 : // The <started_gcs> is an integer in range from 0..kMaxNumberOfGCs that stores
30 : // the number of GCs initiated by the MemoryReducer since it left the DONE
31 : // state.
32 : // The <next_gc_start_ms> is a double that stores the earliest time the next GC
33 : // can be initiated by the MemoryReducer.
34 : // The <last_gc_start_ms> is a double that stores the time of the last full GC.
35 : // The DONE state means that the MemoryReducer is not active.
36 : // The WAIT state means that the MemoryReducer is waiting for mutator allocation
37 : // rate to drop. The check for the allocation rate happens in the timer task
38 : // callback. If the allocation rate does not drop in watchdog_delay_ms since
39 : // the last GC then transition to the RUN state is forced.
40 : // The RUN state means that the MemoryReducer started incremental marking and is
41 : // waiting for it to finish. Incremental marking steps are performed as usual
42 : // in the idle notification and in the mutator.
43 : //
44 : // Transitions:
45 : // DONE t -> WAIT 0 (now_ms + long_delay_ms) t' happens:
46 : // - on context disposal.
47 : // - at the end of mark-compact GC initiated by the mutator.
48 : // This signals that there is potential garbage to be collected.
49 : //
50 : // WAIT n x t -> WAIT n (now_ms + long_delay_ms) t' happens:
51 : // - on mark-compact GC initiated by the mutator,
52 : // - in the timer callback if the mutator allocation rate is high or
53 : // incremental GC is in progress or (now_ms - t < watchdog_delay_ms)
54 : //
55 : // WAIT n x t -> WAIT (n+1) t happens:
56 : // - on background idle notification, which signals that we can start
57 : // incremental marking even if the allocation rate is high.
58 : // The MemoryReducer starts incremental marking on this transition but still
59 : // has a pending timer task.
60 : //
61 : // WAIT n x t -> DONE t happens:
62 : // - in the timer callback if n >= kMaxNumberOfGCs.
63 : //
64 : // WAIT n x t -> RUN (n+1) t happens:
65 : // - in the timer callback if the mutator allocation rate is low
66 : // and now_ms >= x and there is no incremental GC in progress.
67 : // - in the timer callback if (now_ms - t > watchdog_delay_ms) and
68 : // and now_ms >= x and there is no incremental GC in progress.
69 : // The MemoryReducer starts incremental marking on this transition.
70 : //
71 : // RUN n t -> DONE now_ms happens:
72 : // - at end of the incremental GC initiated by the MemoryReducer if
73 : // (n > 1 and there is no more garbage to be collected) or
74 : // n == kMaxNumberOfGCs.
75 : // RUN n t -> WAIT n (now_ms + short_delay_ms) now_ms happens:
76 : // - at end of the incremental GC initiated by the MemoryReducer if
77 : // (n == 1 or there is more garbage to be collected) and
78 : // n < kMaxNumberOfGCs.
79 : //
80 : // now_ms is the current time,
81 : // t' is t if the current event is not a GC event and is now_ms otherwise,
82 : // long_delay_ms, short_delay_ms, and watchdog_delay_ms are constants.
83 : class V8_EXPORT_PRIVATE MemoryReducer {
84 : public:
85 : enum Action { kDone, kWait, kRun };
86 :
87 : struct State {
88 : State(Action action, int started_gcs, double next_gc_start_ms,
89 : double last_gc_time_ms, size_t committed_memory_at_last_run)
90 : : action(action),
91 : started_gcs(started_gcs),
92 : next_gc_start_ms(next_gc_start_ms),
93 : last_gc_time_ms(last_gc_time_ms),
94 79246 : committed_memory_at_last_run(committed_memory_at_last_run) {}
95 : Action action;
96 : int started_gcs;
97 : double next_gc_start_ms;
98 : double last_gc_time_ms;
99 : size_t committed_memory_at_last_run;
100 : };
101 :
102 : enum EventType { kTimer, kMarkCompact, kPossibleGarbage };
103 :
104 : struct Event {
105 : EventType type;
106 : double time_ms;
107 : size_t committed_memory;
108 : bool next_gc_likely_to_collect_more;
109 : bool should_start_incremental_gc;
110 : bool can_start_incremental_gc;
111 : };
112 :
113 : explicit MemoryReducer(Heap* heap);
114 : // Callbacks.
115 : void NotifyMarkCompact(const Event& event);
116 : void NotifyPossibleGarbage(const Event& event);
117 : void NotifyBackgroundIdleNotification(const Event& event);
118 : // The step function that computes the next state from the current state and
119 : // the incoming event.
120 : static State Step(const State& state, const Event& event);
121 : // Posts a timer task that will call NotifyTimer after the given delay.
122 : void ScheduleTimer(double delay_ms);
123 : void TearDown();
124 : static const int kLongDelayMs;
125 : static const int kShortDelayMs;
126 : static const int kWatchdogDelayMs;
127 : static const int kMaxNumberOfGCs;
128 : // The committed memory has to increase by at least this factor since the
129 : // last run in order to trigger a new run after mark-compact.
130 : static const double kCommittedMemoryFactor;
131 : // The committed memory has to increase by at least this amount since the
132 : // last run in order to trigger a new run after mark-compact.
133 : static const size_t kCommittedMemoryDelta;
134 :
135 : Heap* heap() { return heap_; }
136 :
137 : bool ShouldGrowHeapSlowly() {
138 84982 : return state_.action == kDone && state_.started_gcs > 0;
139 : }
140 :
141 : private:
142 2966 : class TimerTask : public v8::internal::CancelableTask {
143 : public:
144 : explicit TimerTask(MemoryReducer* memory_reducer);
145 :
146 : private:
147 : // v8::internal::CancelableTask overrides.
148 : void RunInternal() override;
149 : MemoryReducer* memory_reducer_;
150 : DISALLOW_COPY_AND_ASSIGN(TimerTask);
151 : };
152 :
153 : void NotifyTimer(const Event& event);
154 :
155 : static bool WatchdogGC(const State& state, const Event& event);
156 :
157 : Heap* heap_;
158 : std::shared_ptr<v8::TaskRunner> taskrunner_;
159 : State state_;
160 : unsigned int js_calls_counter_;
161 : double js_calls_sample_time_ms_;
162 :
163 : // Used in cctest.
164 : friend class HeapTester;
165 : DISALLOW_COPY_AND_ASSIGN(MemoryReducer);
166 : };
167 :
168 : } // namespace internal
169 : } // namespace v8
170 :
171 : #endif // V8_HEAP_MEMORY_REDUCER_H_
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