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 #include "src/heap/memory-reducer.h"
6
7 #include "src/flags.h"
8 #include "src/heap/gc-tracer.h"
9 #include "src/heap/heap-inl.h"
10 #include "src/utils.h"
11 #include "src/v8.h"
12
13 namespace v8 {
14 namespace internal {
15
16 const int MemoryReducer::kLongDelayMs = 8000;
17 const int MemoryReducer::kShortDelayMs = 500;
18 const int MemoryReducer::kWatchdogDelayMs = 100000;
19 const int MemoryReducer::kMaxNumberOfGCs = 3;
20
TimerTask(MemoryReducer * memory_reducer)21 MemoryReducer::TimerTask::TimerTask(MemoryReducer* memory_reducer)
22 : CancelableTask(memory_reducer->heap()->isolate()),
23 memory_reducer_(memory_reducer) {}
24
25
RunInternal()26 void MemoryReducer::TimerTask::RunInternal() {
27 const double kJsCallsPerMsThreshold = 0.5;
28 Heap* heap = memory_reducer_->heap();
29 Event event;
30 double time_ms = heap->MonotonicallyIncreasingTimeInMs();
31 heap->tracer()->SampleAllocation(time_ms, heap->NewSpaceAllocationCounter(),
32 heap->OldGenerationAllocationCounter());
33 double js_call_rate = memory_reducer_->SampleAndGetJsCallsPerMs(time_ms);
34 bool low_allocation_rate = heap->HasLowAllocationRate();
35 bool is_idle = js_call_rate < kJsCallsPerMsThreshold && low_allocation_rate;
36 bool optimize_for_memory = heap->ShouldOptimizeForMemoryUsage();
37 if (FLAG_trace_gc_verbose) {
38 PrintIsolate(heap->isolate(), "Memory reducer: call rate %.3lf, %s, %s\n",
39 js_call_rate, low_allocation_rate ? "low alloc" : "high alloc",
40 optimize_for_memory ? "background" : "foreground");
41 }
42 event.type = kTimer;
43 event.time_ms = time_ms;
44 // The memory reducer will start incremental markig if
45 // 1) mutator is likely idle: js call rate is low and allocation rate is low.
46 // 2) mutator is in background: optimize for memory flag is set.
47 event.should_start_incremental_gc = is_idle || optimize_for_memory;
48 event.can_start_incremental_gc =
49 heap->incremental_marking()->IsStopped() &&
50 (heap->incremental_marking()->CanBeActivated() || optimize_for_memory);
51 memory_reducer_->NotifyTimer(event);
52 }
53
54
SampleAndGetJsCallsPerMs(double time_ms)55 double MemoryReducer::SampleAndGetJsCallsPerMs(double time_ms) {
56 unsigned int counter = heap()->isolate()->js_calls_from_api_counter();
57 unsigned int call_delta = counter - js_calls_counter_;
58 double time_delta_ms = time_ms - js_calls_sample_time_ms_;
59 js_calls_counter_ = counter;
60 js_calls_sample_time_ms_ = time_ms;
61 return time_delta_ms > 0 ? call_delta / time_delta_ms : 0;
62 }
63
64
NotifyTimer(const Event & event)65 void MemoryReducer::NotifyTimer(const Event& event) {
66 DCHECK_EQ(kTimer, event.type);
67 DCHECK_EQ(kWait, state_.action);
68 state_ = Step(state_, event);
69 if (state_.action == kRun) {
70 DCHECK(heap()->incremental_marking()->IsStopped());
71 DCHECK(FLAG_incremental_marking);
72 if (FLAG_trace_gc_verbose) {
73 PrintIsolate(heap()->isolate(), "Memory reducer: started GC #%d\n",
74 state_.started_gcs);
75 }
76 heap()->StartIdleIncrementalMarking();
77 } else if (state_.action == kWait) {
78 if (!heap()->incremental_marking()->IsStopped() &&
79 heap()->ShouldOptimizeForMemoryUsage()) {
80 // Make progress with pending incremental marking if memory usage has
81 // higher priority than latency. This is important for background tabs
82 // that do not send idle notifications.
83 const int kIncrementalMarkingDelayMs = 500;
84 double deadline = heap()->MonotonicallyIncreasingTimeInMs() +
85 kIncrementalMarkingDelayMs;
86 heap()->incremental_marking()->AdvanceIncrementalMarking(
87 deadline, i::IncrementalMarking::StepActions(
88 i::IncrementalMarking::NO_GC_VIA_STACK_GUARD,
89 i::IncrementalMarking::FORCE_MARKING,
90 i::IncrementalMarking::FORCE_COMPLETION));
91 heap()->FinalizeIncrementalMarkingIfComplete(
92 "Memory reducer: finalize incremental marking");
93 }
94 // Re-schedule the timer.
95 ScheduleTimer(event.time_ms, state_.next_gc_start_ms - event.time_ms);
96 if (FLAG_trace_gc_verbose) {
97 PrintIsolate(heap()->isolate(), "Memory reducer: waiting for %.f ms\n",
98 state_.next_gc_start_ms - event.time_ms);
99 }
100 }
101 }
102
103
NotifyMarkCompact(const Event & event)104 void MemoryReducer::NotifyMarkCompact(const Event& event) {
105 DCHECK_EQ(kMarkCompact, event.type);
106 Action old_action = state_.action;
107 state_ = Step(state_, event);
108 if (old_action != kWait && state_.action == kWait) {
109 // If we are transitioning to the WAIT state, start the timer.
110 ScheduleTimer(event.time_ms, state_.next_gc_start_ms - event.time_ms);
111 }
112 if (old_action == kRun) {
113 if (FLAG_trace_gc_verbose) {
114 PrintIsolate(heap()->isolate(), "Memory reducer: finished GC #%d (%s)\n",
115 state_.started_gcs,
116 state_.action == kWait ? "will do more" : "done");
117 }
118 }
119 }
120
NotifyPossibleGarbage(const Event & event)121 void MemoryReducer::NotifyPossibleGarbage(const Event& event) {
122 DCHECK_EQ(kPossibleGarbage, event.type);
123 Action old_action = state_.action;
124 state_ = Step(state_, event);
125 if (old_action != kWait && state_.action == kWait) {
126 // If we are transitioning to the WAIT state, start the timer.
127 ScheduleTimer(event.time_ms, state_.next_gc_start_ms - event.time_ms);
128 }
129 }
130
131
WatchdogGC(const State & state,const Event & event)132 bool MemoryReducer::WatchdogGC(const State& state, const Event& event) {
133 return state.last_gc_time_ms != 0 &&
134 event.time_ms > state.last_gc_time_ms + kWatchdogDelayMs;
135 }
136
137
138 // For specification of this function see the comment for MemoryReducer class.
Step(const State & state,const Event & event)139 MemoryReducer::State MemoryReducer::Step(const State& state,
140 const Event& event) {
141 if (!FLAG_incremental_marking || !FLAG_memory_reducer) {
142 return State(kDone, 0, 0, state.last_gc_time_ms);
143 }
144 switch (state.action) {
145 case kDone:
146 if (event.type == kTimer) {
147 return state;
148 } else {
149 DCHECK(event.type == kPossibleGarbage || event.type == kMarkCompact);
150 return State(
151 kWait, 0, event.time_ms + kLongDelayMs,
152 event.type == kMarkCompact ? event.time_ms : state.last_gc_time_ms);
153 }
154 case kWait:
155 switch (event.type) {
156 case kPossibleGarbage:
157 return state;
158 case kTimer:
159 if (state.started_gcs >= kMaxNumberOfGCs) {
160 return State(kDone, kMaxNumberOfGCs, 0.0, state.last_gc_time_ms);
161 } else if (event.can_start_incremental_gc &&
162 (event.should_start_incremental_gc ||
163 WatchdogGC(state, event))) {
164 if (state.next_gc_start_ms <= event.time_ms) {
165 return State(kRun, state.started_gcs + 1, 0.0,
166 state.last_gc_time_ms);
167 } else {
168 return state;
169 }
170 } else {
171 return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
172 state.last_gc_time_ms);
173 }
174 case kMarkCompact:
175 return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
176 event.time_ms);
177 }
178 case kRun:
179 if (event.type != kMarkCompact) {
180 return state;
181 } else {
182 if (state.started_gcs < kMaxNumberOfGCs &&
183 (event.next_gc_likely_to_collect_more || state.started_gcs == 1)) {
184 return State(kWait, state.started_gcs, event.time_ms + kShortDelayMs,
185 event.time_ms);
186 } else {
187 return State(kDone, kMaxNumberOfGCs, 0.0, event.time_ms);
188 }
189 }
190 }
191 UNREACHABLE();
192 return State(kDone, 0, 0, 0.0); // Make the compiler happy.
193 }
194
195
ScheduleTimer(double time_ms,double delay_ms)196 void MemoryReducer::ScheduleTimer(double time_ms, double delay_ms) {
197 DCHECK(delay_ms > 0);
198 // Record the time and the js call counter.
199 SampleAndGetJsCallsPerMs(time_ms);
200 // Leave some room for precision error in task scheduler.
201 const double kSlackMs = 100;
202 v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(heap()->isolate());
203 auto timer_task = new MemoryReducer::TimerTask(this);
204 V8::GetCurrentPlatform()->CallDelayedOnForegroundThread(
205 isolate, timer_task, (delay_ms + kSlackMs) / 1000.0);
206 }
207
208
TearDown()209 void MemoryReducer::TearDown() { state_ = State(kDone, 0, 0, 0.0); }
210
211 } // namespace internal
212 } // namespace v8
213