Author: [email protected]
Date: Thu May 14 01:55:34 2009
New Revision: 1944
Modified:
branches/bleeding_edge/src/heap.cc
branches/bleeding_edge/src/spaces-inl.h
branches/bleeding_edge/src/spaces.cc
branches/bleeding_edge/src/spaces.h
Log:
Reapply r1900, r1897, r1895 with a fix.
When a paged space shrinks by an even multiple of the chunk size,
ensure that the cached last page in the space is updated.
Review URL: http://codereview.chromium.org/113267
Modified: branches/bleeding_edge/src/heap.cc
==============================================================================
--- branches/bleeding_edge/src/heap.cc (original)
+++ branches/bleeding_edge/src/heap.cc Thu May 14 01:55:34 2009
@@ -538,7 +538,7 @@
// Shared state read by the scavenge collector and set by ScavengeObject.
-static Address promoted_top = NULL;
+static Address promoted_rear = NULL;
#ifdef DEBUG
@@ -554,24 +554,34 @@
}
}
};
-#endif
-void Heap::Scavenge() {
-#ifdef DEBUG
- if (FLAG_enable_slow_asserts) {
- VerifyNonPointerSpacePointersVisitor v;
- HeapObjectIterator it(code_space_);
- while (it.has_next()) {
- HeapObject* object = it.next();
- if (object->IsCode()) {
- Code::cast(object)->ConvertICTargetsFromAddressToObject();
- }
+
+static void VerifyNonPointerSpacePointers() {
+ // Verify that there are no pointers to new space in spaces where we
+ // do not expect them.
+ VerifyNonPointerSpacePointersVisitor v;
+ HeapObjectIterator code_it(Heap::code_space());
+ while (code_it.has_next()) {
+ HeapObject* object = code_it.next();
+ if (object->IsCode()) {
+ Code::cast(object)->ConvertICTargetsFromAddressToObject();
+ object->Iterate(&v);
+ Code::cast(object)->ConvertICTargetsFromObjectToAddress();
+ } else {
+ // If we find non-code objects in code space (e.g., free list
+ // nodes) we want to verify them as well.
object->Iterate(&v);
- if (object->IsCode()) {
- Code::cast(object)->ConvertICTargetsFromObjectToAddress();
- }
}
}
+
+ HeapObjectIterator data_it(Heap::old_data_space());
+ while (data_it.has_next()) data_it.next()->Iterate(&v);
+}
+#endif
+
+void Heap::Scavenge() {
+#ifdef DEBUG
+ if (FLAG_enable_slow_asserts) VerifyNonPointerSpacePointers();
#endif
gc_state_ = SCAVENGE;
@@ -596,72 +606,70 @@
new_space_.Flip();
new_space_.ResetAllocationInfo();
- // We need to sweep newly copied objects which can be in either the to
space
- // or the old space. For to space objects, we use a mark. Newly copied
- // objects lie between the mark and the allocation top. For objects
- // promoted to old space, we write their addresses downward from the top
of
- // the new space. Sweeping newly promoted objects requires an allocation
- // pointer and a mark. Note that the allocation pointer 'top' actually
- // moves downward from the high address in the to space.
+ // We need to sweep newly copied objects which can be either in the
+ // to space or promoted to the old generation. For to-space
+ // objects, we treat the bottom of the to space as a queue. Newly
+ // copied and unswept objects lie between a 'front' mark and the
+ // allocation pointer.
//
- // There is guaranteed to be enough room at the top of the to space for
the
- // addresses of promoted objects: every object promoted frees up its
size in
- // bytes from the top of the new space, and objects are at least one
pointer
- // in size. Using the new space to record promoted addresses makes the
- // scavenge collector agnostic to the allocation strategy (eg, linear or
- // free-list) used in old space.
- Address new_mark = new_space_.ToSpaceLow();
- Address promoted_mark = new_space_.ToSpaceHigh();
- promoted_top = new_space_.ToSpaceHigh();
+ // Promoted objects can go into various old-generation spaces, and
+ // can be allocated internally in the spaces (from the free list).
+ // We treat the top of the to space as a queue of addresses of
+ // promoted objects. The addresses of newly promoted and unswept
+ // objects lie between a 'front' mark and a 'rear' mark that is
+ // updated as a side effect of promoting an object.
+ //
+ // There is guaranteed to be enough room at the top of the to space
+ // for the addresses of promoted objects: every object promoted
+ // frees up its size in bytes from the top of the new space, and
+ // objects are at least one pointer in size.
+ Address new_space_front = new_space_.ToSpaceLow();
+ Address promoted_front = new_space_.ToSpaceHigh();
+ promoted_rear = new_space_.ToSpaceHigh();
ScavengeVisitor scavenge_visitor;
// Copy roots.
IterateRoots(&scavenge_visitor);
- // Copy objects reachable from the old generation. By definition, there
- // are no intergenerational pointers in code or data spaces.
+ // Copy objects reachable from weak pointers.
+ GlobalHandles::IterateWeakRoots(&scavenge_visitor);
+
+ // Copy objects reachable from the old generation. By definition,
+ // there are no intergenerational pointers in code or data spaces.
IterateRSet(old_pointer_space_, &ScavengePointer);
IterateRSet(map_space_, &ScavengePointer);
lo_space_->IterateRSet(&ScavengePointer);
- bool has_processed_weak_pointers = false;
-
- while (true) {
- ASSERT(new_mark <= new_space_.top());
- ASSERT(promoted_mark >= promoted_top);
-
- // Copy objects reachable from newly copied objects.
- while (new_mark < new_space_.top() || promoted_mark > promoted_top) {
- // Sweep newly copied objects in the to space. The allocation
pointer
- // can change during sweeping.
- Address previous_top = new_space_.top();
- SemiSpaceIterator new_it(new_space(), new_mark);
- while (new_it.has_next()) {
- new_it.next()->Iterate(&scavenge_visitor);
- }
- new_mark = previous_top;
+ do {
+ ASSERT(new_space_front <= new_space_.top());
+ ASSERT(promoted_front >= promoted_rear);
+
+ // The addresses new_space_front and new_space_.top() define a
+ // queue of unprocessed copied objects. Process them until the
+ // queue is empty.
+ while (new_space_front < new_space_.top()) {
+ HeapObject* object = HeapObject::FromAddress(new_space_front);
+ object->Iterate(&scavenge_visitor);
+ new_space_front += object->Size();
+ }
- // Sweep newly copied objects in the old space. The promotion 'top'
- // pointer could change during sweeping.
- previous_top = promoted_top;
- for (Address current = promoted_mark - kPointerSize;
- current >= previous_top;
- current -= kPointerSize) {
- HeapObject* object = HeapObject::cast(Memory::Object_at(current));
- object->Iterate(&scavenge_visitor);
- UpdateRSet(object);
- }
- promoted_mark = previous_top;
+ // The addresses promoted_front and promoted_rear define a queue
+ // of unprocessed addresses of promoted objects. Process them
+ // until the queue is empty.
+ while (promoted_front > promoted_rear) {
+ promoted_front -= kPointerSize;
+ HeapObject* object =
+ HeapObject::cast(Memory::Object_at(promoted_front));
+ object->Iterate(&scavenge_visitor);
+ UpdateRSet(object);
}
- if (has_processed_weak_pointers) break; // We are done.
- // Copy objects reachable from weak pointers.
- GlobalHandles::IterateWeakRoots(&scavenge_visitor);
- has_processed_weak_pointers = true;
- }
+ // Take another spin if there are now unswept objects in new space
+ // (there are currently no more unswept promoted objects).
+ } while (new_space_front < new_space_.top());
// Set age mark.
- new_space_.set_age_mark(new_mark);
+ new_space_.set_age_mark(new_space_.top());
LOG(ResourceEvent("scavenge", "end"));
@@ -882,8 +890,8 @@
if (target_space == Heap::old_pointer_space_) {
// Record the object's address at the top of the to space, to allow
// it to be swept by the scavenger.
- promoted_top -= kPointerSize;
- Memory::Object_at(promoted_top) = *p;
+ promoted_rear -= kPointerSize;
+ Memory::Object_at(promoted_rear) = *p;
} else {
#ifdef DEBUG
// Objects promoted to the data space should not have pointers to
Modified: branches/bleeding_edge/src/spaces-inl.h
==============================================================================
--- branches/bleeding_edge/src/spaces-inl.h (original)
+++ branches/bleeding_edge/src/spaces-inl.h Thu May 14 01:55:34 2009
@@ -64,15 +64,16 @@
// PageIterator
bool PageIterator::has_next() {
- return cur_page_ != stop_page_;
+ return prev_page_ != stop_page_;
}
Page* PageIterator::next() {
ASSERT(has_next());
- Page* result = cur_page_;
- cur_page_ = cur_page_->next_page();
- return result;
+ prev_page_ = (prev_page_ == NULL)
+ ? space_->first_page_
+ : prev_page_->next_page();
+ return prev_page_;
}
Modified: branches/bleeding_edge/src/spaces.cc
==============================================================================
--- branches/bleeding_edge/src/spaces.cc (original)
+++ branches/bleeding_edge/src/spaces.cc Thu May 14 01:55:34 2009
@@ -111,17 +111,26 @@
//
-----------------------------------------------------------------------------
// PageIterator
-PageIterator::PageIterator(PagedSpace* space, Mode mode) {
- cur_page_ = space->first_page_;
+PageIterator::PageIterator(PagedSpace* space, Mode mode) : space_(space) {
+ prev_page_ = NULL;
switch (mode) {
case PAGES_IN_USE:
- stop_page_ = space->AllocationTopPage()->next_page();
+ stop_page_ = space->AllocationTopPage();
break;
case PAGES_USED_BY_MC:
- stop_page_ = space->MCRelocationTopPage()->next_page();
+ stop_page_ = space->MCRelocationTopPage();
break;
case ALL_PAGES:
- stop_page_ = Page::FromAddress(NULL);
+#ifdef DEBUG
+ // Verify that the cached last page in the space is actually the
+ // last page.
+ for (Page* p = space->first_page_; p->is_valid(); p =
p->next_page()) {
+ if (!p->next_page()->is_valid()) {
+ ASSERT(space->last_page_ == p);
+ }
+ }
+#endif
+ stop_page_ = space->last_page_;
break;
default:
UNREACHABLE();
@@ -496,8 +505,11 @@
accounting_stats_.ExpandSpace(num_pages * Page::kObjectAreaSize);
ASSERT(Capacity() <= max_capacity_);
+ // Sequentially initialize remembered sets in the newly allocated
+ // pages and cache the current last page in the space.
for (Page* p = first_page_; p->is_valid(); p = p->next_page()) {
p->ClearRSet();
+ last_page_ = p;
}
// Use first_page_ for allocation.
@@ -676,9 +688,11 @@
MemoryAllocator::SetNextPage(last_page, p);
- // Clear remembered set of new pages.
+ // Sequentially clear remembered set of new pages and and cache the
+ // new last page in the space.
while (p->is_valid()) {
p->ClearRSet();
+ last_page_ = p;
p = p->next_page();
}
@@ -723,10 +737,13 @@
Page* p = MemoryAllocator::FreePages(last_page_to_keep->next_page());
MemoryAllocator::SetNextPage(last_page_to_keep, p);
- // Since pages are only freed in whole chunks, we may have kept more than
- // pages_to_keep.
+ // Since pages are only freed in whole chunks, we may have kept more
+ // than pages_to_keep. Count the extra pages and cache the new last
+ // page in the space.
+ last_page_ = last_page_to_keep;
while (p->is_valid()) {
pages_to_keep++;
+ last_page_ = p;
p = p->next_page();
}
Modified: branches/bleeding_edge/src/spaces.h
==============================================================================
--- branches/bleeding_edge/src/spaces.h (original)
+++ branches/bleeding_edge/src/spaces.h Thu May 14 01:55:34 2009
@@ -511,11 +511,22 @@
//
// A HeapObjectIterator iterates objects from a given address to the
// top of a space. The given address must be below the current
-// allocation pointer (space top). If the space top changes during
-// iteration (because of allocating new objects), the iterator does
-// not iterate new objects. The caller function must create a new
-// iterator starting from the old top in order to visit these new
-// objects. Heap::Scavenage() is such an example.
+// allocation pointer (space top). There are some caveats.
+//
+// (1) If the space top changes upward during iteration (because of
+// allocating new objects), the iterator does not iterate objects
+// above the original space top. The caller must create a new
+// iterator starting from the old top in order to visit these new
+// objects.
+//
+// (2) If new objects are allocated below the original allocation top
+// (e.g., free-list allocation in paged spaces), the new objects
+// may or may not be iterated depending on their position with
+// respect to the current point of iteration.
+//
+// (3) The space top should not change downward during iteration,
+// otherwise the iterator will return not-necessarily-valid
+// objects.
class HeapObjectIterator: public ObjectIterator {
public:
@@ -559,17 +570,35 @@
//
-----------------------------------------------------------------------------
-// A PageIterator iterates pages in a space.
+// A PageIterator iterates the pages in a paged space.
//
// The PageIterator class provides three modes for iterating pages in a
space:
-// PAGES_IN_USE iterates pages that are in use by the allocator;
-// PAGES_USED_BY_GC iterates pages that hold relocated objects during a
-// mark-compact collection;
+// PAGES_IN_USE iterates pages containing allocated objects.
+// PAGES_USED_BY_MC iterates pages that hold relocated objects during a
+// mark-compact collection.
// ALL_PAGES iterates all pages in the space.
+//
+// There are some caveats.
+//
+// (1) If the space expands during iteration, new pages will not be
+// returned by the iterator in any mode.
+//
+// (2) If new objects are allocated during iteration, they will appear
+// in pages returned by the iterator. Allocation may cause the
+// allocation pointer or MC allocation pointer in the last page to
+// change between constructing the iterator and iterating the last
+// page.
+//
+// (3) The space should not shrink during iteration, otherwise the
+// iterator will return deallocated pages.
class PageIterator BASE_EMBEDDED {
public:
- enum Mode {PAGES_IN_USE, PAGES_USED_BY_MC, ALL_PAGES};
+ enum Mode {
+ PAGES_IN_USE,
+ PAGES_USED_BY_MC,
+ ALL_PAGES
+ };
PageIterator(PagedSpace* space, Mode mode);
@@ -577,8 +606,9 @@
inline Page* next();
private:
- Page* cur_page_; // next page to return
- Page* stop_page_; // page where to stop
+ PagedSpace* space_;
+ Page* prev_page_; // Previous page returned.
+ Page* stop_page_; // Page to stop at (last page returned by the
iterator).
};
@@ -808,6 +838,10 @@
// The first page in this space.
Page* first_page_;
+
+ // The last page in this space. Initially set in Setup, updated in
+ // Expand and Shrink.
+ Page* last_page_;
// Normal allocation information.
AllocationInfo allocation_info_;
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