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
13namespace v8 {
14namespace internal {
15
16const int MemoryReducer::kLongDelayMs = 8000;
17const int MemoryReducer::kShortDelayMs = 500;
18const int MemoryReducer::kWatchdogDelayMs = 100000;
19const int MemoryReducer::kMaxNumberOfGCs = 3;
20const double MemoryReducer::kCommittedMemoryFactor = 1.1;
21const size_t MemoryReducer::kCommittedMemoryDelta = 10 * MB;
22
23MemoryReducer::TimerTask::TimerTask(MemoryReducer* memory_reducer)
24    : CancelableTask(memory_reducer->heap()->isolate()),
25      memory_reducer_(memory_reducer) {}
26
27
28void MemoryReducer::TimerTask::RunInternal() {
29  Heap* heap = memory_reducer_->heap();
30  Event event;
31  double time_ms = heap->MonotonicallyIncreasingTimeInMs();
32  heap->tracer()->SampleAllocation(time_ms, heap->NewSpaceAllocationCounter(),
33                                   heap->OldGenerationAllocationCounter());
34  bool low_allocation_rate = heap->HasLowAllocationRate();
35  bool optimize_for_memory = heap->ShouldOptimizeForMemoryUsage();
36  if (FLAG_trace_gc_verbose) {
37    heap->isolate()->PrintWithTimestamp(
38        "Memory reducer: %s, %s\n",
39        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 =
48      low_allocation_rate || optimize_for_memory;
49  event.can_start_incremental_gc =
50      heap->incremental_marking()->IsStopped() &&
51      (heap->incremental_marking()->CanBeActivated() || optimize_for_memory);
52  event.committed_memory = heap->CommittedOldGenerationMemory();
53  memory_reducer_->NotifyTimer(event);
54}
55
56
57void MemoryReducer::NotifyTimer(const Event& event) {
58  DCHECK_EQ(kTimer, event.type);
59  DCHECK_EQ(kWait, state_.action);
60  state_ = Step(state_, event);
61  if (state_.action == kRun) {
62    DCHECK(heap()->incremental_marking()->IsStopped());
63    DCHECK(FLAG_incremental_marking);
64    if (FLAG_trace_gc_verbose) {
65      heap()->isolate()->PrintWithTimestamp("Memory reducer: started GC #%d\n",
66                                            state_.started_gcs);
67    }
68    heap()->StartIdleIncrementalMarking(
69        GarbageCollectionReason::kMemoryReducer);
70  } else if (state_.action == kWait) {
71    if (!heap()->incremental_marking()->IsStopped() &&
72        heap()->ShouldOptimizeForMemoryUsage()) {
73      // Make progress with pending incremental marking if memory usage has
74      // higher priority than latency. This is important for background tabs
75      // that do not send idle notifications.
76      const int kIncrementalMarkingDelayMs = 500;
77      double deadline = heap()->MonotonicallyIncreasingTimeInMs() +
78                        kIncrementalMarkingDelayMs;
79      heap()->incremental_marking()->AdvanceIncrementalMarking(
80          deadline, IncrementalMarking::NO_GC_VIA_STACK_GUARD,
81          IncrementalMarking::FORCE_COMPLETION, StepOrigin::kTask);
82      heap()->FinalizeIncrementalMarkingIfComplete(
83          GarbageCollectionReason::kFinalizeMarkingViaTask);
84    }
85    // Re-schedule the timer.
86    ScheduleTimer(event.time_ms, state_.next_gc_start_ms - event.time_ms);
87    if (FLAG_trace_gc_verbose) {
88      heap()->isolate()->PrintWithTimestamp(
89          "Memory reducer: waiting for %.f ms\n",
90          state_.next_gc_start_ms - event.time_ms);
91    }
92  }
93}
94
95
96void MemoryReducer::NotifyMarkCompact(const Event& event) {
97  DCHECK_EQ(kMarkCompact, event.type);
98  Action old_action = state_.action;
99  state_ = Step(state_, event);
100  if (old_action != kWait && state_.action == kWait) {
101    // If we are transitioning to the WAIT state, start the timer.
102    ScheduleTimer(event.time_ms, state_.next_gc_start_ms - event.time_ms);
103  }
104  if (old_action == kRun) {
105    if (FLAG_trace_gc_verbose) {
106      heap()->isolate()->PrintWithTimestamp(
107          "Memory reducer: finished GC #%d (%s)\n", state_.started_gcs,
108          state_.action == kWait ? "will do more" : "done");
109    }
110  }
111}
112
113void MemoryReducer::NotifyPossibleGarbage(const Event& event) {
114  DCHECK_EQ(kPossibleGarbage, event.type);
115  Action old_action = state_.action;
116  state_ = Step(state_, event);
117  if (old_action != kWait && state_.action == kWait) {
118    // If we are transitioning to the WAIT state, start the timer.
119    ScheduleTimer(event.time_ms, state_.next_gc_start_ms - event.time_ms);
120  }
121}
122
123
124bool MemoryReducer::WatchdogGC(const State& state, const Event& event) {
125  return state.last_gc_time_ms != 0 &&
126         event.time_ms > state.last_gc_time_ms + kWatchdogDelayMs;
127}
128
129
130// For specification of this function see the comment for MemoryReducer class.
131MemoryReducer::State MemoryReducer::Step(const State& state,
132                                         const Event& event) {
133  if (!FLAG_incremental_marking || !FLAG_memory_reducer) {
134    return State(kDone, 0, 0, state.last_gc_time_ms, 0);
135  }
136  switch (state.action) {
137    case kDone:
138      if (event.type == kTimer) {
139        return state;
140      } else if (event.type == kMarkCompact) {
141        if (event.committed_memory <
142            Max(static_cast<size_t>(state.committed_memory_at_last_run *
143                                    kCommittedMemoryFactor),
144                state.committed_memory_at_last_run + kCommittedMemoryDelta)) {
145          return state;
146        } else {
147          return State(kWait, 0, event.time_ms + kLongDelayMs,
148                       event.type == kMarkCompact ? event.time_ms
149                                                  : state.last_gc_time_ms,
150                       0);
151        }
152      } else {
153        DCHECK_EQ(kPossibleGarbage, event.type);
154        return State(
155            kWait, 0, event.time_ms + kLongDelayMs,
156            event.type == kMarkCompact ? event.time_ms : state.last_gc_time_ms,
157            0);
158      }
159    case kWait:
160      switch (event.type) {
161        case kPossibleGarbage:
162          return state;
163        case kTimer:
164          if (state.started_gcs >= kMaxNumberOfGCs) {
165            return State(kDone, kMaxNumberOfGCs, 0.0, state.last_gc_time_ms,
166                         event.committed_memory);
167          } else if (event.can_start_incremental_gc &&
168                     (event.should_start_incremental_gc ||
169                      WatchdogGC(state, event))) {
170            if (state.next_gc_start_ms <= event.time_ms) {
171              return State(kRun, state.started_gcs + 1, 0.0,
172                           state.last_gc_time_ms, 0);
173            } else {
174              return state;
175            }
176          } else {
177            return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
178                         state.last_gc_time_ms, 0);
179          }
180        case kMarkCompact:
181          return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
182                       event.time_ms, 0);
183      }
184    case kRun:
185      if (event.type != kMarkCompact) {
186        return state;
187      } else {
188        if (state.started_gcs < kMaxNumberOfGCs &&
189            (event.next_gc_likely_to_collect_more || state.started_gcs == 1)) {
190          return State(kWait, state.started_gcs, event.time_ms + kShortDelayMs,
191                       event.time_ms, 0);
192        } else {
193          return State(kDone, kMaxNumberOfGCs, 0.0, event.time_ms,
194                       event.committed_memory);
195        }
196      }
197  }
198  UNREACHABLE();
199  return State(kDone, 0, 0, 0.0, 0);  // Make the compiler happy.
200}
201
202
203void MemoryReducer::ScheduleTimer(double time_ms, double delay_ms) {
204  DCHECK(delay_ms > 0);
205  // Leave some room for precision error in task scheduler.
206  const double kSlackMs = 100;
207  v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(heap()->isolate());
208  auto timer_task = new MemoryReducer::TimerTask(this);
209  V8::GetCurrentPlatform()->CallDelayedOnForegroundThread(
210      isolate, timer_task, (delay_ms + kSlackMs) / 1000.0);
211}
212
213void MemoryReducer::TearDown() { state_ = State(kDone, 0, 0, 0.0, 0); }
214
215}  // namespace internal
216}  // namespace v8
217