Reland "Replace reduce-memory mode in idle notification with delayed clean-up GC."

src/heap/memory-reducer.cc

+// 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::kMaxNumberOfGCs = 3;
+
+
+void MemoryReducer::TimerTask::Run() {
+  Heap* heap = memory_reducer_->heap();
+  Event event;
+  event.type = kTimer;
+  event.time_ms = heap->MonotonicallyIncreasingTimeInMs();
+  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_EQ(kTimer, event.type);
+  DCHECK_EQ(kWait, state_.action);
+  state_ = Step(state_, event);
+  if (state_.action == kRun) {
+    DCHECK(heap()->incremental_marking()->IsStopped());
+    DCHECK(FLAG_incremental_marking);
+    heap()->StartIdleIncrementalMarking();
+    if (FLAG_trace_gc_verbose) {
+      PrintIsolate(heap()->isolate(), "Memory reducer: started GC #%d\n",
+                   state_.started_gcs);
+    }
+  } else if (state_.action == kWait) {
+    // 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);
+  }
+}
+
+
+// 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);
+  }
+  switch (state.action) {
+    case kDone:
+      if (event.type == kTimer) {
+        return state;
+      } else {
+        DCHECK(event.type == kContextDisposed || event.type == kMarkCompact);
+        return State(kWait, 0, event.time_ms + kLongDelayMs);
+      }
+    case kWait:
+      if (event.type == kContextDisposed) {
+        return state;
+      } else if (event.type == kTimer && event.can_start_incremental_gc &&
+                 event.low_allocation_rate) {
+        if (state.next_gc_start_ms <= event.time_ms) {
+          return State(kRun, state.started_gcs + 1, 0.0);
+        } else {
+          return state;
+        }
+      } else {
+        return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs);
+      }
+    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);
+        } else {
+          return State(kDone, 0, 0.0);
+        }
+      }
+  }
+  UNREACHABLE();
+  return State(kDone, 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());
+  V8::GetCurrentPlatform()->CallDelayedOnForegroundThread(
+      isolate, new MemoryReducer::TimerTask(this),
+      (delay_ms + kSlackMs) / 1000.0);
+}
+
+}  // internal
+}  // v8