Basic implementation of incremental marking.

src/incremental-marking.h

+// Copyright 2010 the V8 project authors. All rights reserved.

[Erik Corry, 2011/02/22 12:27:19]

2011

+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_INCREMENTAL_MARKING_H_
+#define V8_INCREMENTAL_MARKING_H_
+
+
+#include "execution.h"
+#include "mark-compact.h"
+#include "objects.h"
+
+namespace v8 {
+namespace internal {
+
+
+class IncrementalMarking : public AllStatic {
+ public:
+  enum State {
+    STOPPED,
+    MARKING,
+    COMPLETE
+  };
+
+  static void Start() {

[Erik Corry, 2011/02/22 12:27:19]

I think it would be cleaner to move largish functions that are not inline/not
called very often into the .cc file.  This includes Start() and Hurry().

[Vyacheslav Egorov (Chromium), 2011/02/23 14:31:46]

Done.

+    if (FLAG_trace_incremental_marking) {
+      PrintF("[IncrementalMarking] Start\n");
+    }
+    ASSERT(FLAG_incremental_marking);
+    ASSERT(state_ == STOPPED);
+    state_ = MARKING;
+
+    // Initialize marking stack.
+    marking_stack_.Initialize(Heap::new_space()->FromSpaceLow(),
+                              Heap::new_space()->FromSpaceHigh());
+
+    // Clear markbits.
+    Address new_space_top = Heap::new_space()->top();
+    Address new_space_bottom = Heap::new_space()->bottom();
+
+    Marking::ClearRange(new_space_bottom,
+                        static_cast<int>(new_space_top - new_space_bottom));
+
+    ClearMarkbits();
+
+#ifdef DEBUG
+    VerifyMarkbitsAreClean();
+#endif
+
+    // Mark strong roots grey.
+    RootMarkingVisitor visitor;
+    Heap::IterateStrongRoots(&visitor, VISIT_ONLY_STRONG);
+
+    // Ready to start incremental marking.
+    if (FLAG_trace_incremental_marking) {
+      PrintF("[IncrementalMarking] Running\n");
+    }
+  }
+
+  static State state() {
+    ASSERT(state_ == STOPPED || FLAG_incremental_marking);
+    return state_;
+  }
+
+  static void Stop() {
+    state_ = STOPPED;

[Erik Corry, 2011/02/22 12:27:19]

Fits on one line.

[Vyacheslav Egorov (Chromium), 2011/02/23 14:31:46]

Done.

+  }
+
+  static void Hurry() {
+    if (state() == MARKING) {
+      if (FLAG_trace_incremental_marking) {
+        PrintF("[IncrementalMarking] Hurry\n");
+      }
+      // TODO(gc) hurry can mark objects it encounters black as mutator
+      // was stopped.
+      while (!marking_stack_.is_empty()) {
+        HeapObject* obj = marking_stack_.Pop();
+        obj->Iterate(&visitor_);
+        MarkBlack(obj);
+      }
+      state_ = COMPLETE;
+      if (FLAG_trace_incremental_marking) {
+        PrintF("[IncrementalMarking] Complete (hurry)\n");
+      }
+    }
+  }
+
+  static void Finalize() {
+    Hurry();
+    state_ = STOPPED;
+    ASSERT(marking_stack_.is_empty());
+  }
+
+
+  static void MarkingComplete() {
+    state_ = COMPLETE;
+    // We completed marking.
+    if (FLAG_trace_incremental_marking) {
+      PrintF("[IncrementalMarking] Complete (normal)\n");
+    }
+    StackGuard::RequestGC();
+  }
+
+
+  static const intptr_t kAllocatedThreshold = 1024;
+  static const intptr_t kFactor = 8;

[Erik Corry, 2011/02/22 12:27:19]

Perhaps call this kAllocationMarkingFactor.

[Vyacheslav Egorov (Chromium), 2011/02/23 14:31:46]

Done.

+
+  static void Step(intptr_t allocated) {
+    if (state_ == MARKING) {
+      allocated_ += allocated;
+
+      if (allocated_ >= kAllocatedThreshold) {
+        intptr_t bytes_to_process = allocated_ * kFactor;
+        int count = 0;
+        double start = 0;
+        if (FLAG_trace_incremental_marking) {
+          PrintF("[IncrementalMarking] Marking %d bytes\n", bytes_to_process);
+          start = OS::TimeCurrentMillis();
+        }
+        while (!marking_stack_.is_empty() && bytes_to_process > 0) {
+          HeapObject* obj = marking_stack_.Pop();
+          ASSERT(IsGrey(obj));
+          Map* map = obj->map();
+          int size = obj->SizeFromMap(map);
+          bytes_to_process -= size;
+          if (IsWhite(map)) WhiteToGrey(map);
+          obj->IterateBody(map->instance_type(), size, &visitor_);
+          MarkBlack(obj);
+          count++;
+        }
+        if (FLAG_trace_incremental_marking) {
+          double end = OS::TimeCurrentMillis();
+          PrintF("[IncrementalMarking]     %d objects marked, spent %d ms\n",
+                 count,
+                 static_cast<int>(end - start));
+        }
+        allocated_ = 0;
+        if (marking_stack_.is_empty()) MarkingComplete();
+      }
+    }
+  }
+
+  static void RecordWrite(HeapObject* obj, Object* value) {
+    if (state_ != STOPPED && value->IsHeapObject()) {
+      if (IsBlack(obj) && IsWhite(HeapObject::cast(value))) {
+        BlackToGrey(obj);
+        if (state_ == COMPLETE) {
+          state_ = MARKING;
+          if (FLAG_trace_incremental_marking) {
+            PrintF("[IncrementalMarking] Restarting (new grey objects)\n");
+          }
+        }
+      }
+    }
+  }
+
+  static void RecordWriteOf(HeapObject* value) {
+    if (state_ != STOPPED) {
+      if (IsWhite(value)) {
+        WhiteToGrey(value);
+        if (state_ == COMPLETE) {
+          state_ = MARKING;
+          if (FLAG_trace_incremental_marking) {
+            PrintF("[IncrementalMarking] Restarting (new grey objects)\n");
+          }
+        }
+      }
+    }
+  }
+
+
+  static void RecordWrites(HeapObject* obj) {
+    if (state_ != STOPPED) {
+      if (IsBlack(obj)) {
+        BlackToGrey(obj);
+        if (state_ == COMPLETE) {
+          state_ = MARKING;
+          if (FLAG_trace_incremental_marking) {
+            PrintF("[IncrementalMarking] Restarting (new grey objects)\n");
+          }
+        }
+      }
+    }
+  }
+
+
+  // Black markbits: 10
+  static inline bool IsBlack(HeapObject* obj) {
+    return Marking::IsMarked(obj->address());

[Erik Corry, 2011/02/22 12:27:19]

Assert that the other bit is not marked?

+  }
+
+  // White markbits: 00
+  static inline bool IsWhite(HeapObject* obj) {
+    return !Marking::IsMarked(obj->address()) &&
+        !Marking::IsMarked(obj->address() + kPointerSize);
+  }
+
+  // Grey markbits: 01

[Erik Corry, 2011/02/22 12:27:19]

Probably should be 11 when we handle overflow.

[Vyacheslav Egorov (Chromium), 2011/02/23 14:31:46]

Yes. Will investigate when we start handling overflow.

+  static inline bool IsGrey(HeapObject* obj) {
+    return Marking::IsMarked(obj->address() + kPointerSize);

[Erik Corry, 2011/02/22 12:27:19]

Assert that the other bit is not marked?

+  }
+
+  static inline void BlackToGrey(HeapObject* obj) {
+    ASSERT(IsBlack(obj));
+    Marking::ClearMark(obj->address());
+    Marking::SetMark(obj->address() + kPointerSize);
+    ASSERT(IsGrey(obj));
+
+    marking_stack_.Push(obj);
+    ASSERT(!marking_stack_.overflowed());
+  }
+
+  static inline void WhiteToGrey(HeapObject* obj) {
+    ASSERT(IsWhite(obj));
+    Marking::SetMark(obj->address() + kPointerSize);
+    ASSERT(IsGrey(obj));
+
+    marking_stack_.Push(obj);
+    ASSERT(!marking_stack_.overflowed());
+  }
+
+  static inline void MarkBlack(HeapObject* obj) {
+    Marking::SetMark(obj->address());
+    Marking::ClearMark(obj->address() + kPointerSize);
+    ASSERT(IsBlack(obj));
+  }
+
+  static inline const char* ColorStr(HeapObject* obj) {
+    if (IsBlack(obj)) return "black";
+    if (IsWhite(obj)) return "white";
+    if (IsGrey(obj)) return "grey";
+    return "???";

[Erik Corry, 2011/02/22 12:27:19]

UNREACHABLE()?

[Vyacheslav Egorov (Chromium), 2011/02/23 14:31:46]

Done.

+  }
+
+ private:
+  static intptr_t allocated_;
+  static State state_;
+  static MarkingStack marking_stack_;
+
+  class MarkingVisitor : public ObjectVisitor {
+   public:
+    void VisitPointer(Object** p) {
+      MarkObjectByPointer(p);
+    }
+
+    void VisitPointers(Object** start, Object** end) {
+      for (Object** p = start; p < end; p++) MarkObjectByPointer(p);
+    }
+
+   private:
+    // Mark object pointed to by p.
+    INLINE(static void MarkObjectByPointer(Object** p)) {
+      if ((*p)->IsHeapObject()) {
+        HeapObject* object = HeapObject::cast(*p);
+        if (IsWhite(object)) WhiteToGrey(object);
+      }
+    }
+  };
+
+
+  class RootMarkingVisitor : public ObjectVisitor {
+   public:
+    void VisitPointer(Object** p) {
+      MarkObjectByPointer(p);
+    }
+
+    void VisitPointers(Object** start, Object** end) {
+      for (Object** p = start; p < end; p++) MarkObjectByPointer(p);
+    }
+
+   private:
+    void MarkObjectByPointer(Object** p) {
+      if (!(*p)->IsHeapObject()) return;
+
+      HeapObject* object = HeapObject::cast(*p);
+      if (!IsWhite(object)) return;
+
+      Map* map = object->map();
+
+      WhiteToGrey(object);

[Erik Corry, 2011/02/22 12:27:19]

This pushes the object onto the stack.  When it is popped the map will be
marked.

[Vyacheslav Egorov (Chromium), 2011/02/23 14:31:46]

Done.

+
+      if (IsWhite(map)) WhiteToGrey(map);

[Erik Corry, 2011/02/22 12:27:19]

Here we also mark the map.  Aren't we doing it twice?

[Vyacheslav Egorov (Chromium), 2011/02/23 14:31:46]

Done.

+    }
+  };
+
+
+  static void ClearMarkbits(PagedSpace* space) {
+    PageIterator it(space, PageIterator::PAGES_IN_USE);
+
+    while (it.has_next()) {
+      Page* p = it.next();
+      p->markbits()->Clear();
+    }
+  }
+
+
+  static void ClearMarkbits() {
+    // We are sweeping code and map spaces precisely so clearing is not required.

[Erik Corry, 2011/02/22 12:27:19]

lint?

[Vyacheslav Egorov (Chromium), 2011/02/23 14:31:46]

Done.

+    ClearMarkbits(Heap::old_pointer_space());
+    ClearMarkbits(Heap::old_data_space());
+    ClearMarkbits(Heap::cell_space());
+  }
+
+
+#ifdef DEBUG
+  static void VerifyMarkbitsAreClean(PagedSpace* space) {
+    PageIterator it(space, PageIterator::PAGES_IN_USE);
+
+    while (it.has_next()) {
+      Page* p = it.next();
+      ASSERT(p->markbits()->IsClean());
+    }
+  }
+
+  static void VerifyMarkbitsAreClean() {
+    VerifyMarkbitsAreClean(Heap::old_pointer_space());
+    VerifyMarkbitsAreClean(Heap::old_data_space());
+    VerifyMarkbitsAreClean(Heap::code_space());
+    VerifyMarkbitsAreClean(Heap::cell_space());
+    VerifyMarkbitsAreClean(Heap::map_space());
+  }
+#endif
+
+  static MarkingVisitor visitor_;
+};
+
+} }  // namespace v8::internal
+
+#endif  // V8_INCREMENTAL_MARKING_H_