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 const double MemoryReducer::kCommittedMemoryFactor = 1.1;
21 const size_t MemoryReducer::kCommittedMemoryDelta = 10 * MB;
22 
MemoryReducer(Heap * heap)23 MemoryReducer::MemoryReducer(Heap* heap)
24     : heap_(heap),
25       taskrunner_(V8::GetCurrentPlatform()->GetForegroundTaskRunner(
26           reinterpret_cast<v8::Isolate*>(heap->isolate()))),
27       state_(kDone, 0, 0.0, 0.0, 0),
28       js_calls_counter_(0),
29       js_calls_sample_time_ms_(0.0) {}
30 
TimerTask(MemoryReducer * memory_reducer)31 MemoryReducer::TimerTask::TimerTask(MemoryReducer* memory_reducer)
32     : CancelableTask(memory_reducer->heap()->isolate()),
33       memory_reducer_(memory_reducer) {}
34 
35 
RunInternal()36 void MemoryReducer::TimerTask::RunInternal() {
37   Heap* heap = memory_reducer_->heap();
38   Event event;
39   double time_ms = heap->MonotonicallyIncreasingTimeInMs();
40   heap->tracer()->SampleAllocation(time_ms, heap->NewSpaceAllocationCounter(),
41                                    heap->OldGenerationAllocationCounter());
42   bool low_allocation_rate = heap->HasLowAllocationRate();
43   bool optimize_for_memory = heap->ShouldOptimizeForMemoryUsage();
44   if (FLAG_trace_gc_verbose) {
45     heap->isolate()->PrintWithTimestamp(
46         "Memory reducer: %s, %s\n",
47         low_allocation_rate ? "low alloc" : "high alloc",
48         optimize_for_memory ? "background" : "foreground");
49   }
50   event.type = kTimer;
51   event.time_ms = time_ms;
52   // The memory reducer will start incremental markig if
53   // 1) mutator is likely idle: js call rate is low and allocation rate is low.
54   // 2) mutator is in background: optimize for memory flag is set.
55   event.should_start_incremental_gc =
56       low_allocation_rate || optimize_for_memory;
57   event.can_start_incremental_gc =
58       heap->incremental_marking()->IsStopped() &&
59       (heap->incremental_marking()->CanBeActivated() || optimize_for_memory);
60   event.committed_memory = heap->CommittedOldGenerationMemory();
61   memory_reducer_->NotifyTimer(event);
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       heap()->isolate()->PrintWithTimestamp("Memory reducer: started GC #%d\n",
74                                             state_.started_gcs);
75     }
76     heap()->StartIdleIncrementalMarking(
77         GarbageCollectionReason::kMemoryReducer,
78         kGCCallbackFlagCollectAllExternalMemory);
79   } else if (state_.action == kWait) {
80     if (!heap()->incremental_marking()->IsStopped() &&
81         heap()->ShouldOptimizeForMemoryUsage()) {
82       // Make progress with pending incremental marking if memory usage has
83       // higher priority than latency. This is important for background tabs
84       // that do not send idle notifications.
85       const int kIncrementalMarkingDelayMs = 500;
86       double deadline = heap()->MonotonicallyIncreasingTimeInMs() +
87                         kIncrementalMarkingDelayMs;
88       heap()->incremental_marking()->AdvanceIncrementalMarking(
89           deadline, IncrementalMarking::NO_GC_VIA_STACK_GUARD,
90           StepOrigin::kTask);
91       heap()->FinalizeIncrementalMarkingIfComplete(
92           GarbageCollectionReason::kFinalizeMarkingViaTask);
93     }
94     // Re-schedule the timer.
95     ScheduleTimer(state_.next_gc_start_ms - event.time_ms);
96     if (FLAG_trace_gc_verbose) {
97       heap()->isolate()->PrintWithTimestamp(
98           "Memory reducer: waiting for %.f ms\n",
99           state_.next_gc_start_ms - event.time_ms);
100     }
101   }
102 }
103 
104 
NotifyMarkCompact(const Event & event)105 void MemoryReducer::NotifyMarkCompact(const Event& event) {
106   DCHECK_EQ(kMarkCompact, event.type);
107   Action old_action = state_.action;
108   state_ = Step(state_, event);
109   if (old_action != kWait && state_.action == kWait) {
110     // If we are transitioning to the WAIT state, start the timer.
111     ScheduleTimer(state_.next_gc_start_ms - event.time_ms);
112   }
113   if (old_action == kRun) {
114     if (FLAG_trace_gc_verbose) {
115       heap()->isolate()->PrintWithTimestamp(
116           "Memory reducer: finished GC #%d (%s)\n", state_.started_gcs,
117           state_.action == kWait ? "will do more" : "done");
118     }
119   }
120 }
121 
NotifyPossibleGarbage(const Event & event)122 void MemoryReducer::NotifyPossibleGarbage(const Event& event) {
123   DCHECK_EQ(kPossibleGarbage, event.type);
124   Action old_action = state_.action;
125   state_ = Step(state_, event);
126   if (old_action != kWait && state_.action == kWait) {
127     // If we are transitioning to the WAIT state, start the timer.
128     ScheduleTimer(state_.next_gc_start_ms - event.time_ms);
129   }
130 }
131 
132 
WatchdogGC(const State & state,const Event & event)133 bool MemoryReducer::WatchdogGC(const State& state, const Event& event) {
134   return state.last_gc_time_ms != 0 &&
135          event.time_ms > state.last_gc_time_ms + kWatchdogDelayMs;
136 }
137 
138 
139 // For specification of this function see the comment for MemoryReducer class.
Step(const State & state,const Event & event)140 MemoryReducer::State MemoryReducer::Step(const State& state,
141                                          const Event& event) {
142   if (!FLAG_incremental_marking || !FLAG_memory_reducer) {
143     return State(kDone, 0, 0, state.last_gc_time_ms, 0);
144   }
145   switch (state.action) {
146     case kDone:
147       if (event.type == kTimer) {
148         return state;
149       } else if (event.type == kMarkCompact) {
150         if (event.committed_memory <
151             Max(static_cast<size_t>(state.committed_memory_at_last_run *
152                                     kCommittedMemoryFactor),
153                 state.committed_memory_at_last_run + kCommittedMemoryDelta)) {
154           return state;
155         } else {
156           return State(kWait, 0, event.time_ms + kLongDelayMs,
157                        event.type == kMarkCompact ? event.time_ms
158                                                   : state.last_gc_time_ms,
159                        0);
160         }
161       } else {
162         DCHECK_EQ(kPossibleGarbage, event.type);
163         return State(
164             kWait, 0, event.time_ms + kLongDelayMs,
165             event.type == kMarkCompact ? event.time_ms : state.last_gc_time_ms,
166             0);
167       }
168     case kWait:
169       switch (event.type) {
170         case kPossibleGarbage:
171           return state;
172         case kTimer:
173           if (state.started_gcs >= kMaxNumberOfGCs) {
174             return State(kDone, kMaxNumberOfGCs, 0.0, state.last_gc_time_ms,
175                          event.committed_memory);
176           } else if (event.can_start_incremental_gc &&
177                      (event.should_start_incremental_gc ||
178                       WatchdogGC(state, event))) {
179             if (state.next_gc_start_ms <= event.time_ms) {
180               return State(kRun, state.started_gcs + 1, 0.0,
181                            state.last_gc_time_ms, 0);
182             } else {
183               return state;
184             }
185           } else {
186             return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
187                          state.last_gc_time_ms, 0);
188           }
189         case kMarkCompact:
190           return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
191                        event.time_ms, 0);
192       }
193     case kRun:
194       if (event.type != kMarkCompact) {
195         return state;
196       } else {
197         if (state.started_gcs < kMaxNumberOfGCs &&
198             (event.next_gc_likely_to_collect_more || state.started_gcs == 1)) {
199           return State(kWait, state.started_gcs, event.time_ms + kShortDelayMs,
200                        event.time_ms, 0);
201         } else {
202           return State(kDone, kMaxNumberOfGCs, 0.0, event.time_ms,
203                        event.committed_memory);
204         }
205       }
206   }
207   UNREACHABLE();
208 }
209 
ScheduleTimer(double delay_ms)210 void MemoryReducer::ScheduleTimer(double delay_ms) {
211   DCHECK_LT(0, delay_ms);
212   if (heap()->IsTearingDown()) return;
213   // Leave some room for precision error in task scheduler.
214   const double kSlackMs = 100;
215   taskrunner_->PostDelayedTask(
216       base::make_unique<MemoryReducer::TimerTask>(this),
217       (delay_ms + kSlackMs) / 1000.0);
218 }
219 
TearDown()220 void MemoryReducer::TearDown() { state_ = State(kDone, 0, 0, 0.0, 0); }
221 
222 }  // namespace internal
223 }  // namespace v8
224