1 files changed, 241 insertions, 0 deletions
diff --git a/deps/v8/src/heap/memory-reducer.cc b/deps/v8/src/heap/memory-reducer.cc
new file mode 100644
index 0000000000..e226f09a04
--- /dev/null
+++ b/deps/v8/src/heap/memory-reducer.cc
@@ -0,0 +1,241 @@
+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/heap/memory-reducer.h"
+
+#include "src/flags.h"
+#include "src/heap/heap.h"
+#include "src/utils.h"
+#include "src/v8.h"
+
+namespace v8 {
+namespace internal {
+
+const int MemoryReducer::kLongDelayMs = 5000;
+const int MemoryReducer::kShortDelayMs = 500;
+const int MemoryReducer::kWatchdogDelayMs = 100000;
+const int MemoryReducer::kMaxNumberOfGCs = 3;
+
+
+void MemoryReducer::TimerTask::Run() {
+  if (heap_is_torn_down_) return;
+  Heap* heap = memory_reducer_->heap();
+  Event event;
+  double time_ms = heap->MonotonicallyIncreasingTimeInMs();
+  heap->tracer()->SampleAllocation(time_ms, heap->NewSpaceAllocationCounter(),
+                                   heap->OldGenerationAllocationCounter());
+  event.type = kTimer;
+  event.time_ms = time_ms;
+  event.low_allocation_rate = heap->HasLowAllocationRate();
+  event.can_start_incremental_gc =
+      heap->incremental_marking()->IsStopped() &&
+      heap->incremental_marking()->CanBeActivated();
+  memory_reducer_->NotifyTimer(event);
+}
+
+
+void MemoryReducer::NotifyTimer(const Event& event) {
+  DCHECK(nullptr != pending_task_);
+  DCHECK_EQ(kTimer, event.type);
+  DCHECK_EQ(kWait, state_.action);
+  pending_task_ = nullptr;
+  state_ = Step(state_, event);
+  if (state_.action == kRun) {
+    DCHECK(heap()->incremental_marking()->IsStopped());
+    DCHECK(FLAG_incremental_marking);
+    if (FLAG_trace_gc_verbose) {
+      PrintIsolate(heap()->isolate(), "Memory reducer: started GC #%d\n",
+                   state_.started_gcs);
+    }
+    if (heap()->ShouldOptimizeForMemoryUsage()) {
+      // Do full GC if memory usage has higher priority than latency. This is
+      // important for background tabs that do not send idle notifications.
+      heap()->CollectAllGarbage(Heap::kReduceMemoryFootprintMask,
+                                "memory reducer");
+    } else {
+      heap()->StartIdleIncrementalMarking();
+    }
+  } else if (state_.action == kWait) {
+    if (!heap()->incremental_marking()->IsStopped() &&
+        heap()->ShouldOptimizeForMemoryUsage()) {
+      // Make progress with pending incremental marking if memory usage has
+      // higher priority than latency. This is important for background tabs
+      // that do not send idle notifications.
+      const int kIncrementalMarkingDelayMs = 500;
+      double deadline = heap()->MonotonicallyIncreasingTimeInMs() +
+                        kIncrementalMarkingDelayMs;
+      heap()->AdvanceIncrementalMarking(
+          0, deadline, i::IncrementalMarking::StepActions(
+                           i::IncrementalMarking::NO_GC_VIA_STACK_GUARD,
+                           i::IncrementalMarking::FORCE_MARKING,
+                           i::IncrementalMarking::FORCE_COMPLETION));
+      heap()->FinalizeIncrementalMarkingIfComplete(
+          "Memory reducer: finalize incremental marking");
+    }
+    // Re-schedule the timer.
+    ScheduleTimer(state_.next_gc_start_ms - event.time_ms);
+    if (FLAG_trace_gc_verbose) {
+      PrintIsolate(heap()->isolate(), "Memory reducer: waiting for %.f ms\n",
+                   state_.next_gc_start_ms - event.time_ms);
+    }
+  }
+}
+
+
+void MemoryReducer::NotifyMarkCompact(const Event& event) {
+  DCHECK_EQ(kMarkCompact, event.type);
+  Action old_action = state_.action;
+  state_ = Step(state_, event);
+  if (old_action != kWait && state_.action == kWait) {
+    // If we are transitioning to the WAIT state, start the timer.
+    ScheduleTimer(state_.next_gc_start_ms - event.time_ms);
+  }
+  if (old_action == kRun) {
+    if (FLAG_trace_gc_verbose) {
+      PrintIsolate(heap()->isolate(), "Memory reducer: finished GC #%d (%s)\n",
+                   state_.started_gcs,
+                   state_.action == kWait ? "will do more" : "done");
+    }
+  }
+}
+
+
+void MemoryReducer::NotifyContextDisposed(const Event& event) {
+  DCHECK_EQ(kContextDisposed, event.type);
+  Action old_action = state_.action;
+  state_ = Step(state_, event);
+  if (old_action != kWait && state_.action == kWait) {
+    // If we are transitioning to the WAIT state, start the timer.
+    ScheduleTimer(state_.next_gc_start_ms - event.time_ms);
+  }
+}
+
+
+void MemoryReducer::NotifyBackgroundIdleNotification(const Event& event) {
+  DCHECK_EQ(kBackgroundIdleNotification, event.type);
+  Action old_action = state_.action;
+  int old_started_gcs = state_.started_gcs;
+  state_ = Step(state_, event);
+  if (old_action == kWait && state_.action == kWait &&
+      old_started_gcs + 1 == state_.started_gcs) {
+    DCHECK(heap()->incremental_marking()->IsStopped());
+    // TODO(ulan): Replace it with incremental marking GC once
+    // chromium:490559 is fixed.
+    if (event.time_ms > state_.last_gc_time_ms + kLongDelayMs) {
+      heap()->CollectAllGarbage(Heap::kReduceMemoryFootprintMask,
+                                "memory reducer background GC");
+    } else {
+      DCHECK(FLAG_incremental_marking);
+      heap()->StartIdleIncrementalMarking();
+      if (FLAG_trace_gc_verbose) {
+        PrintIsolate(heap()->isolate(),
+                     "Memory reducer: started GC #%d"
+                     " (background idle)\n",
+                     state_.started_gcs);
+      }
+    }
+  }
+}
+
+
+bool MemoryReducer::WatchdogGC(const State& state, const Event& event) {
+  return state.last_gc_time_ms != 0 &&
+         event.time_ms > state.last_gc_time_ms + kWatchdogDelayMs;
+}
+
+
+// For specification of this function see the comment for MemoryReducer class.
+MemoryReducer::State MemoryReducer::Step(const State& state,
+                                         const Event& event) {
+  if (!FLAG_incremental_marking) {
+    return State(kDone, 0, 0, state.last_gc_time_ms);
+  }
+  switch (state.action) {
+    case kDone:
+      if (event.type == kTimer || event.type == kBackgroundIdleNotification) {
+        return state;
+      } else {
+        DCHECK(event.type == kContextDisposed || event.type == kMarkCompact);
+        return State(
+            kWait, 0, event.time_ms + kLongDelayMs,
+            event.type == kMarkCompact ? event.time_ms : state.last_gc_time_ms);
+      }
+    case kWait:
+      switch (event.type) {
+        case kContextDisposed:
+          return state;
+        case kTimer:
+          if (state.started_gcs >= kMaxNumberOfGCs) {
+            return State(kDone, kMaxNumberOfGCs, 0.0, state.last_gc_time_ms);
+          } else if (event.can_start_incremental_gc &&
+                     (event.low_allocation_rate || WatchdogGC(state, event))) {
+            if (state.next_gc_start_ms <= event.time_ms) {
+              return State(kRun, state.started_gcs + 1, 0.0,
+                           state.last_gc_time_ms);
+            } else {
+              return state;
+            }
+          } else {
+            return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
+                         state.last_gc_time_ms);
+          }
+        case kBackgroundIdleNotification:
+          if (event.can_start_incremental_gc &&
+              state.started_gcs < kMaxNumberOfGCs) {
+            return State(kWait, state.started_gcs + 1,
+                         event.time_ms + kLongDelayMs, state.last_gc_time_ms);
+          } else {
+            return state;
+          }
+        case kMarkCompact:
+          return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
+                       event.time_ms);
+      }
+    case kRun:
+      if (event.type != kMarkCompact) {
+        return state;
+      } else {
+        if (state.started_gcs < kMaxNumberOfGCs &&
+            (event.next_gc_likely_to_collect_more || state.started_gcs == 1)) {
+          return State(kWait, state.started_gcs, event.time_ms + kShortDelayMs,
+                       event.time_ms);
+        } else {
+          return State(kDone, kMaxNumberOfGCs, 0.0, event.time_ms);
+        }
+      }
+  }
+  UNREACHABLE();
+  return State(kDone, 0, 0, 0.0);  // Make the compiler happy.
+}
+
+
+void MemoryReducer::ScheduleTimer(double delay_ms) {
+  DCHECK(delay_ms > 0);
+  // Leave some room for precision error in task scheduler.
+  const double kSlackMs = 100;
+  v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(heap()->isolate());
+  DCHECK(nullptr == pending_task_);
+  pending_task_ = new MemoryReducer::TimerTask(this);
+  V8::GetCurrentPlatform()->CallDelayedOnForegroundThread(
+      isolate, pending_task_, (delay_ms + kSlackMs) / 1000.0);
+}
+
+
+void MemoryReducer::ClearTask(v8::Task* task) {
+  if (pending_task_ == task) {
+    pending_task_ = nullptr;
+  }
+}
+
+
+void MemoryReducer::TearDown() {
+  if (pending_task_ != nullptr) {
+    pending_task_->NotifyHeapTearDown();
+    pending_task_ = nullptr;
+  }
+  state_ = State(kDone, 0, 0, 0.0);
+}
+
+}  // internal
+}  // v8