v8/src/global-handles.h
antonm@chromium.org 20938fc53c Attempt to collect more garbage before panicking with out of memory.
Currently weak handles retain an object for another GC round (oftem times,
major GC round.)  Instrumenting Chromium shows that navigation leaves
many global objects which are only collected in next go.  Let's
attempt to collect more garbage when approacing OOM condition.

This is a better version of rolled out r5455: now it's correctly
rebuilds object groups between additional GCs.

Review URL: http://codereview.chromium.org/4295004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5761 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
2010-11-03 13:00:28 +00:00

182 lines
6.9 KiB
C++

// Copyright 2007-2008 the V8 project authors. All rights reserved.
// 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_GLOBAL_HANDLES_H_
#define V8_GLOBAL_HANDLES_H_
#include "list-inl.h"
namespace v8 {
namespace internal {
// Structure for tracking global handles.
// A single list keeps all the allocated global handles.
// Destroyed handles stay in the list but is added to the free list.
// At GC the destroyed global handles are removed from the free list
// and deallocated.
// Callback function on handling weak global handles.
// typedef bool (*WeakSlotCallback)(Object** pointer);
// An object group is treated like a single JS object: if one of object in
// the group is alive, all objects in the same group are considered alive.
// An object group is used to simulate object relationship in a DOM tree.
class ObjectGroup : public Malloced {
public:
ObjectGroup() : objects_(4) {}
explicit ObjectGroup(size_t capacity)
: objects_(static_cast<int>(capacity)) { }
List<Object**> objects_;
};
typedef void (*WeakReferenceGuest)(Object* object, void* parameter);
class GlobalHandles : public AllStatic {
public:
// Creates a new global handle that is alive until Destroy is called.
static Handle<Object> Create(Object* value);
// Destroy a global handle.
static void Destroy(Object** location);
// Make the global handle weak and set the callback parameter for the
// handle. When the garbage collector recognizes that only weak global
// handles point to an object the handles are cleared and the callback
// function is invoked (for each handle) with the handle and corresponding
// parameter as arguments. Note: cleared means set to Smi::FromInt(0). The
// reason is that Smi::FromInt(0) does not change during garage collection.
static void MakeWeak(Object** location,
void* parameter,
WeakReferenceCallback callback);
// Returns the current number of weak handles.
static int NumberOfWeakHandles() { return number_of_weak_handles_; }
static void RecordStats(HeapStats* stats);
// Returns the current number of weak handles to global objects.
// These handles are also included in NumberOfWeakHandles().
static int NumberOfGlobalObjectWeakHandles() {
return number_of_global_object_weak_handles_;
}
// Clear the weakness of a global handle.
static void ClearWeakness(Object** location);
// Tells whether global handle is near death.
static bool IsNearDeath(Object** location);
// Tells whether global handle is weak.
static bool IsWeak(Object** location);
// Process pending weak handles.
// Returns true if next major GC is likely to collect more garbage.
static bool PostGarbageCollectionProcessing();
// Iterates over all strong handles.
static void IterateStrongRoots(ObjectVisitor* v);
// Iterates over all handles.
static void IterateAllRoots(ObjectVisitor* v);
// Iterates over all weak roots in heap.
static void IterateWeakRoots(ObjectVisitor* v);
// Iterates over weak roots that are bound to a given callback.
static void IterateWeakRoots(WeakReferenceGuest f,
WeakReferenceCallback callback);
// Find all weak handles satisfying the callback predicate, mark
// them as pending.
static void IdentifyWeakHandles(WeakSlotCallback f);
// Add an object group.
// Should only used in GC callback function before a collection.
// All groups are destroyed after a mark-compact collection.
static void AddGroup(Object*** handles, size_t length);
// Returns the object groups.
static List<ObjectGroup*>* ObjectGroups();
// Remove bags, this should only happen after GC.
static void RemoveObjectGroups();
// Tear down the global handle structure.
static void TearDown();
#ifdef DEBUG
static void PrintStats();
static void Print();
#endif
class Pool;
private:
// Internal node structure, one for each global handle.
class Node;
// Field always containing the number of weak and near-death handles.
static int number_of_weak_handles_;
// Field always containing the number of weak and near-death handles
// to global objects. These objects are also included in
// number_of_weak_handles_.
static int number_of_global_object_weak_handles_;
// Global handles are kept in a single linked list pointed to by head_.
static Node* head_;
static Node* head() { return head_; }
static void set_head(Node* value) { head_ = value; }
// Free list for DESTROYED global handles not yet deallocated.
static Node* first_free_;
static Node* first_free() { return first_free_; }
static void set_first_free(Node* value) { first_free_ = value; }
// List of deallocated nodes.
// Deallocated nodes form a prefix of all the nodes and
// |first_deallocated| points to last deallocated node before
// |head|. Those deallocated nodes are additionally linked
// by |next_free|:
// 1st deallocated head
// | |
// V V
// node node ... node node
// .next -> .next -> .next ->
// <- .next_free <- .next_free <- .next_free
static Node* first_deallocated_;
static Node* first_deallocated() { return first_deallocated_; }
static void set_first_deallocated(Node* value) {
first_deallocated_ = value;
}
};
} } // namespace v8::internal
#endif // V8_GLOBAL_HANDLES_H_