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 : namespace heap {
17 : class HeapTester;
18 : } // namespace heap
19 :
20 : class Heap;
21 :
22 :
23 : // The goal of the MemoryReducer class is to detect transition of the mutator
24 : // from high allocation phase to low allocation phase and to collect potential
25 : // garbage created in the high allocation phase.
26 : //
27 : // The class implements an automaton with the following states and transitions.
28 : //
29 : // States:
30 : // - DONE <last_gc_time_ms>
31 : // - WAIT <started_gcs> <next_gc_start_ms> <last_gc_time_ms>
32 : // - RUN <started_gcs> <last_gc_time_ms>
33 : // The <started_gcs> is an integer in range from 0..kMaxNumberOfGCs that stores
34 : // the number of GCs initiated by the MemoryReducer since it left the DONE
35 : // state.
36 : // The <next_gc_start_ms> is a double that stores the earliest time the next GC
37 : // can be initiated by the MemoryReducer.
38 : // The <last_gc_start_ms> is a double that stores the time of the last full GC.
39 : // The DONE state means that the MemoryReducer is not active.
40 : // The WAIT state means that the MemoryReducer is waiting for mutator allocation
41 : // rate to drop. The check for the allocation rate happens in the timer task
42 : // callback. If the allocation rate does not drop in watchdog_delay_ms since
43 : // the last GC then transition to the RUN state is forced.
44 : // The RUN state means that the MemoryReducer started incremental marking and is
45 : // waiting for it to finish. Incremental marking steps are performed as usual
46 : // in the idle notification and in the mutator.
47 : //
48 : // Transitions:
49 : // DONE t -> WAIT 0 (now_ms + long_delay_ms) t' happens:
50 : // - on context disposal.
51 : // - at the end of mark-compact GC initiated by the mutator.
52 : // This signals that there is potential garbage to be collected.
53 : //
54 : // WAIT n x t -> WAIT n (now_ms + long_delay_ms) t' happens:
55 : // - on mark-compact GC initiated by the mutator,
56 : // - in the timer callback if the mutator allocation rate is high or
57 : // incremental GC is in progress or (now_ms - t < watchdog_delay_ms)
58 : //
59 : // WAIT n x t -> WAIT (n+1) t happens:
60 : // - on background idle notification, which signals that we can start
61 : // incremental marking even if the allocation rate is high.
62 : // The MemoryReducer starts incremental marking on this transition but still
63 : // has a pending timer task.
64 : //
65 : // WAIT n x t -> DONE t happens:
66 : // - in the timer callback if n >= kMaxNumberOfGCs.
67 : //
68 : // WAIT n x t -> RUN (n+1) t happens:
69 : // - in the timer callback if the mutator allocation rate is low
70 : // and now_ms >= x and there is no incremental GC in progress.
71 : // - in the timer callback if (now_ms - t > watchdog_delay_ms) and
72 : // and now_ms >= x and there is no incremental GC in progress.
73 : // The MemoryReducer starts incremental marking on this transition.
74 : //
75 : // RUN n t -> DONE now_ms happens:
76 : // - at end of the incremental GC initiated by the MemoryReducer if
77 : // (n > 1 and there is no more garbage to be collected) or
78 : // n == kMaxNumberOfGCs.
79 : // RUN n t -> WAIT n (now_ms + short_delay_ms) now_ms happens:
80 : // - at end of the incremental GC initiated by the MemoryReducer if
81 : // (n == 1 or there is more garbage to be collected) and
82 : // n < kMaxNumberOfGCs.
83 : //
84 : // now_ms is the current time,
85 : // t' is t if the current event is not a GC event and is now_ms otherwise,
86 : // long_delay_ms, short_delay_ms, and watchdog_delay_ms are constants.
87 62409 : class V8_EXPORT_PRIVATE MemoryReducer {
88 : public:
89 : enum Action { kDone, kWait, kRun };
90 :
91 : struct State {
92 : State(Action action, int started_gcs, double next_gc_start_ms,
93 : double last_gc_time_ms, size_t committed_memory_at_last_run)
94 : : action(action),
95 : started_gcs(started_gcs),
96 : next_gc_start_ms(next_gc_start_ms),
97 : last_gc_time_ms(last_gc_time_ms),
98 78525 : committed_memory_at_last_run(committed_memory_at_last_run) {}
99 : Action action;
100 : int started_gcs;
101 : double next_gc_start_ms;
102 : double last_gc_time_ms;
103 : size_t committed_memory_at_last_run;
104 : };
105 :
106 : enum EventType { kTimer, kMarkCompact, kPossibleGarbage };
107 :
108 : struct Event {
109 : EventType type;
110 : double time_ms;
111 : size_t committed_memory;
112 : bool next_gc_likely_to_collect_more;
113 : bool should_start_incremental_gc;
114 : bool can_start_incremental_gc;
115 : };
116 :
117 : explicit MemoryReducer(Heap* heap);
118 : // Callbacks.
119 : void NotifyMarkCompact(const Event& event);
120 : void NotifyPossibleGarbage(const Event& event);
121 : void NotifyBackgroundIdleNotification(const Event& event);
122 : // The step function that computes the next state from the current state and
123 : // the incoming event.
124 : static State Step(const State& state, const Event& event);
125 : // Posts a timer task that will call NotifyTimer after the given delay.
126 : void ScheduleTimer(double delay_ms);
127 : void TearDown();
128 : static const int kLongDelayMs;
129 : static const int kShortDelayMs;
130 : static const int kWatchdogDelayMs;
131 : static const int kMaxNumberOfGCs;
132 : // The committed memory has to increase by at least this factor since the
133 : // last run in order to trigger a new run after mark-compact.
134 : static const double kCommittedMemoryFactor;
135 : // The committed memory has to increase by at least this amount since the
136 : // last run in order to trigger a new run after mark-compact.
137 : static const size_t kCommittedMemoryDelta;
138 :
139 : Heap* heap() { return heap_; }
140 :
141 : bool ShouldGrowHeapSlowly() {
142 70028 : return state_.action == kDone && state_.started_gcs > 0;
143 : }
144 :
145 : private:
146 5026 : class TimerTask : public v8::internal::CancelableTask {
147 : public:
148 : explicit TimerTask(MemoryReducer* memory_reducer);
149 :
150 : private:
151 : // v8::internal::CancelableTask overrides.
152 : void RunInternal() override;
153 : MemoryReducer* memory_reducer_;
154 : DISALLOW_COPY_AND_ASSIGN(TimerTask);
155 : };
156 :
157 : void NotifyTimer(const Event& event);
158 :
159 : static bool WatchdogGC(const State& state, const Event& event);
160 :
161 : Heap* heap_;
162 : std::shared_ptr<v8::TaskRunner> taskrunner_;
163 : State state_;
164 : unsigned int js_calls_counter_;
165 : double js_calls_sample_time_ms_;
166 :
167 : // Used in cctest.
168 : friend class heap::HeapTester;
169 : DISALLOW_COPY_AND_ASSIGN(MemoryReducer);
170 : };
171 :
172 : } // namespace internal
173 : } // namespace v8
174 :
175 : #endif // V8_HEAP_MEMORY_REDUCER_H_
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