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      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 
     21 MemoryReducer::TimerTask::TimerTask(MemoryReducer* memory_reducer)
     22     : CancelableTask(memory_reducer->heap()->isolate()),
     23       memory_reducer_(memory_reducer) {}
     24 
     25 
     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 
     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 
     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 
    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 
    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 
    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.
    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 
    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 
    209 void MemoryReducer::TearDown() { state_ = State(kDone, 0, 0, 0.0); }
    210 
    211 }  // namespace internal
    212 }  // namespace v8
    213