Revision: 15621
Author: [email protected]
Date: Thu Jul 11 04:24:38 2013
Log: Perform new space evacuation based on marking bits.
BUG=
[email protected]
Review URL: https://codereview.chromium.org/18531004
http://code.google.com/p/v8/source/detail?r=15621
Modified:
/branches/bleeding_edge/src/mark-compact.cc
/branches/bleeding_edge/src/mark-compact.h
=======================================
--- /branches/bleeding_edge/src/mark-compact.cc Thu Jul 11 02:17:03 2013
+++ /branches/bleeding_edge/src/mark-compact.cc Thu Jul 11 04:24:38 2013
@@ -1987,6 +1987,81 @@
grey_objects >>= (Bitmap::kBitsPerCell - 1);
}
}
+
+
+int MarkCompactCollector::DiscoverAndPromoteBlackObjectsOnPage(
+ NewSpace* new_space,
+ NewSpacePage* p) {
+ ASSERT(strcmp(Marking::kWhiteBitPattern, "00") == 0);
+ ASSERT(strcmp(Marking::kBlackBitPattern, "10") == 0);
+ ASSERT(strcmp(Marking::kGreyBitPattern, "11") == 0);
+ ASSERT(strcmp(Marking::kImpossibleBitPattern, "01") == 0);
+
+ MarkBit::CellType* cells = p->markbits()->cells();
+ int survivors_size = 0;
+
+ int last_cell_index =
+ Bitmap::IndexToCell(
+ Bitmap::CellAlignIndex(
+ p->AddressToMarkbitIndex(p->area_end())));
+
+ Address cell_base = p->area_start();
+ int cell_index = Bitmap::IndexToCell(
+ Bitmap::CellAlignIndex(
+ p->AddressToMarkbitIndex(cell_base)));
+
+ for (;
+ cell_index < last_cell_index;
+ cell_index++, cell_base += 32 * kPointerSize) {
+ ASSERT(static_cast<unsigned>(cell_index) ==
+ Bitmap::IndexToCell(
+ Bitmap::CellAlignIndex(
+ p->AddressToMarkbitIndex(cell_base))));
+
+ MarkBit::CellType current_cell = cells[cell_index];
+ if (current_cell == 0) continue;
+
+ int offset = 0;
+ while (current_cell != 0) {
+ int trailing_zeros =
CompilerIntrinsics::CountTrailingZeros(current_cell);
+ current_cell >>= trailing_zeros;
+ offset += trailing_zeros;
+ Address address = cell_base + offset * kPointerSize;
+ HeapObject* object = HeapObject::FromAddress(address);
+
+ int size = object->Size();
+ survivors_size += size;
+
+ offset++;
+ current_cell >>= 1;
+ // Aggressively promote young survivors to the old space.
+ if (TryPromoteObject(object, size)) {
+ continue;
+ }
+
+ // Promotion failed. Just migrate object to another semispace.
+ MaybeObject* allocation = new_space->AllocateRaw(size);
+ if (allocation->IsFailure()) {
+ if (!new_space->AddFreshPage()) {
+ // Shouldn't happen. We are sweeping linearly, and to-space
+ // has the same number of pages as from-space, so there is
+ // always room.
+ UNREACHABLE();
+ }
+ allocation = new_space->AllocateRaw(size);
+ ASSERT(!allocation->IsFailure());
+ }
+ Object* target = allocation->ToObjectUnchecked();
+
+ MigrateObject(HeapObject::cast(target)->address(),
+ object->address(),
+ size,
+ NEW_SPACE);
+ }
+ cells[cell_index] = 0;
+ }
+ return survivors_size;
+}
static void DiscoverGreyObjectsInSpace(Heap* heap,
@@ -2895,42 +2970,10 @@
// migrate live objects and write forwarding addresses. This stage puts
// new entries in the store buffer and may cause some pages to be marked
// scan-on-scavenge.
- SemiSpaceIterator from_it(from_bottom, from_top);
- for (HeapObject* object = from_it.Next();
- object != NULL;
- object = from_it.Next()) {
- MarkBit mark_bit = Marking::MarkBitFrom(object);
- if (mark_bit.Get()) {
- mark_bit.Clear();
- // Don't bother decrementing live bytes count. We'll discard the
- // entire page at the end.
- int size = object->Size();
- survivors_size += size;
-
- // Aggressively promote young survivors to the old space.
- if (TryPromoteObject(object, size)) {
- continue;
- }
-
- // Promotion failed. Just migrate object to another semispace.
- MaybeObject* allocation = new_space->AllocateRaw(size);
- if (allocation->IsFailure()) {
- if (!new_space->AddFreshPage()) {
- // Shouldn't happen. We are sweeping linearly, and to-space
- // has the same number of pages as from-space, so there is
- // always room.
- UNREACHABLE();
- }
- allocation = new_space->AllocateRaw(size);
- ASSERT(!allocation->IsFailure());
- }
- Object* target = allocation->ToObjectUnchecked();
-
- MigrateObject(HeapObject::cast(target)->address(),
- object->address(),
- size,
- NEW_SPACE);
- }
+ NewSpacePageIterator it(from_bottom, from_top);
+ while (it.has_next()) {
+ NewSpacePage* p = it.next();
+ survivors_size += DiscoverAndPromoteBlackObjectsOnPage(new_space, p);
}
heap_->IncrementYoungSurvivorsCounter(survivors_size);
=======================================
--- /branches/bleeding_edge/src/mark-compact.h Tue Jul 2 08:15:58 2013
+++ /branches/bleeding_edge/src/mark-compact.h Thu Jul 11 04:24:38 2013
@@ -919,6 +919,9 @@
// regions to each space's free list.
void SweepSpaces();
+ int DiscoverAndPromoteBlackObjectsOnPage(NewSpace* new_space,
+ NewSpacePage* p);
+
void EvacuateNewSpace();
void EvacuateLiveObjectsFromPage(Page* p);
--
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