Don't unlink evacuation candidates before sweeping, move them to the end of their list of pages.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/256743004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@21042 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mark-compact.cc

@@ -3176,7 +3176,6 @@ void MarkCompactCollector::EvacuatePages() {
           slots_buffer_allocator_.DeallocateChain(page->slots_buffer_address());
           page->ClearEvacuationCandidate();
           page->SetFlag(Page::RESCAN_ON_EVACUATION);
-          page->InsertAfter(static_cast<PagedSpace*>(page->owner())->anchor());
         }
         return;
       }
@@ -3667,14 +3666,14 @@ void MarkCompactCollector::EvacuateNewSpaceAndCandidates() {
 }
 
 
-void MarkCompactCollector::UnlinkEvacuationCandidates() {
+void MarkCompactCollector::MoveEvacuationCandidatesToEndOfPagesList() {
   int npages = evacuation_candidates_.length();
   for (int i = 0; i < npages; i++) {
     Page* p = evacuation_candidates_[i];
     if (!p->IsEvacuationCandidate()) continue;
     p->Unlink();
-    p->ClearSweptPrecisely();
-    p->ClearSweptConservatively();
+    PagedSpace* space = static_cast<PagedSpace*>(p->owner());
+    p->InsertAfter(space->LastPage());
   }
 }
 
@@ -3689,7 +3688,7 @@ void MarkCompactCollector::ReleaseEvacuationCandidates() {
     p->set_scan_on_scavenge(false);
     slots_buffer_allocator_.DeallocateChain(p->slots_buffer_address());
     p->ResetLiveBytes();
-    space->ReleasePage(p, false);
+    space->ReleasePage(p);
   }
   evacuation_candidates_.Rewind(0);
   compacting_ = false;
@@ -4113,6 +4112,7 @@ void MarkCompactCollector::SweepInParallel(PagedSpace* space) {
       free_list->Concatenate(&private_free_list);
       p->set_parallel_sweeping(MemoryChunk::PARALLEL_SWEEPING_FINALIZE);
     }
+    if (p == space->end_of_unswept_pages()) break;
   }
 }
 
@@ -4123,6 +4123,10 @@ void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
                                       sweeper == CONCURRENT_CONSERVATIVE);
   space->ClearStats();
 
+  // We defensively initialize end_of_unswept_pages_ here with the first page
+  // of the pages list.
+  space->set_end_of_unswept_pages(space->FirstPage());
+
   PageIterator it(space);
 
   int pages_swept = 0;
@@ -4131,15 +4135,14 @@ void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
 
   while (it.has_next()) {
     Page* p = it.next();
-
     ASSERT(p->parallel_sweeping() == MemoryChunk::PARALLEL_SWEEPING_DONE);
-    ASSERT(!p->IsEvacuationCandidate());
 
     // Clear sweeping flags indicating that marking bits are still intact.
     p->ClearSweptPrecisely();
     p->ClearSweptConservatively();
 
-    if (p->IsFlagSet(Page::RESCAN_ON_EVACUATION)) {
+    if (p->IsFlagSet(Page::RESCAN_ON_EVACUATION) ||
+        p->IsEvacuationCandidate()) {
       // Will be processed in EvacuateNewSpaceAndCandidates.
       ASSERT(evacuation_candidates_.length() > 0);
       continue;
@@ -4155,7 +4158,7 @@ void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
         // Adjust unswept free bytes because releasing a page expects said
         // counter to be accurate for unswept pages.
         space->IncreaseUnsweptFreeBytes(p);
-        space->ReleasePage(p, true);
+        space->ReleasePage(p);
         continue;
       }
       unused_page_present = true;
@@ -4189,6 +4192,7 @@ void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
           p->set_parallel_sweeping(MemoryChunk::PARALLEL_SWEEPING_PENDING);
           space->IncreaseUnsweptFreeBytes(p);
         }
+        space->set_end_of_unswept_pages(p);
         break;
       }
       case PRECISE: {
@@ -4238,9 +4242,7 @@ void MarkCompactCollector::SweepSpaces() {
   }
   if (sweep_precisely_) how_to_sweep = PRECISE;
 
-  // Unlink evacuation candidates before sweeper threads access the list of
-  // pages to avoid race condition.
-  UnlinkEvacuationCandidates();
+  MoveEvacuationCandidatesToEndOfPagesList();
 
   // Noncompacting collections simply sweep the spaces to clear the mark
   // bits and free the nonlive blocks (for old and map spaces).  We sweep

src/mark-compact.h

@@ -704,9 +704,6 @@ class MarkCompactCollector {
   void RemoveDeadInvalidatedCode();
   void ProcessInvalidatedCode(ObjectVisitor* visitor);
 
-  void UnlinkEvacuationCandidates();
-  void ReleaseEvacuationCandidates();
-
   void StartSweeperThreads();
 
 #ifdef DEBUG
@@ -895,6 +892,12 @@ class MarkCompactCollector {
 
   void EvacuateNewSpaceAndCandidates();
 
+  void ReleaseEvacuationCandidates();
+
+  // Moves the pages of the evacuation_candidates_ list to the end of their
+  // corresponding space pages list.
+  void MoveEvacuationCandidatesToEndOfPagesList();
+
   void SweepSpace(PagedSpace* space, SweeperType sweeper);
 
   // Finalizes the parallel sweeping phase. Marks all the pages that were

src/spaces.cc

@@ -559,10 +559,6 @@ void MemoryChunk::InsertAfter(MemoryChunk* other) {
 
 
 void MemoryChunk::Unlink() {
-  if (!InNewSpace() && IsFlagSet(SCAN_ON_SCAVENGE)) {
-    heap_->decrement_scan_on_scavenge_pages();
-    ClearFlag(SCAN_ON_SCAVENGE);
-  }
   MemoryChunk* next_element = next_chunk();
   MemoryChunk* prev_element = prev_chunk();
   next_element->set_prev_chunk(prev_element);
@@ -930,7 +926,8 @@ PagedSpace::PagedSpace(Heap* heap,
     : Space(heap, id, executable),
       free_list_(this),
       was_swept_conservatively_(false),
-      unswept_free_bytes_(0) {
+      unswept_free_bytes_(0),
+      end_of_unswept_pages_(NULL) {
   if (id == CODE_SPACE) {
     area_size_ = heap->isolate()->memory_allocator()->
         CodePageAreaSize();
@@ -1103,7 +1100,7 @@ void PagedSpace::IncreaseCapacity(int size) {
 }
 
 
-void PagedSpace::ReleasePage(Page* page, bool unlink) {
+void PagedSpace::ReleasePage(Page* page) {
   ASSERT(page->LiveBytes() == 0);
   ASSERT(AreaSize() == page->area_size());
 
@@ -1115,6 +1112,11 @@ void PagedSpace::ReleasePage(Page* page, bool unlink) {
     DecreaseUnsweptFreeBytes(page);
   }
 
+  if (page->IsFlagSet(MemoryChunk::SCAN_ON_SCAVENGE)) {
+    heap()->decrement_scan_on_scavenge_pages();
+    page->ClearFlag(MemoryChunk::SCAN_ON_SCAVENGE);
+  }
+
   ASSERT(!free_list_.ContainsPageFreeListItems(page));
 
   if (Page::FromAllocationTop(allocation_info_.top()) == page) {
@@ -1122,9 +1124,7 @@ void PagedSpace::ReleasePage(Page* page, bool unlink) {
     allocation_info_.set_limit(NULL);
   }
 
-  if (unlink) {
-    page->Unlink();
-  }
+  page->Unlink();
   if (page->IsFlagSet(MemoryChunk::CONTAINS_ONLY_DATA)) {
     heap()->isolate()->memory_allocator()->Free(page);
   } else {

src/spaces.h

@@ -1831,7 +1831,7 @@ class PagedSpace : public Space {
   void IncreaseCapacity(int size);
 
   // Releases an unused page and shrinks the space.
-  void ReleasePage(Page* page, bool unlink);
+  void ReleasePage(Page* page);
 
   // The dummy page that anchors the linked list of pages.
   Page* anchor() { return &anchor_; }
@@ -1891,6 +1891,20 @@ class PagedSpace : public Space {
     unswept_free_bytes_ = 0;
   }
 
+  // This function tries to steal size_in_bytes memory from the sweeper threads
+  // free-lists. If it does not succeed stealing enough memory, it will wait
+  // for the sweeper threads to finish sweeping.
+  // It returns true when sweeping is completed and false otherwise.
+  bool EnsureSweeperProgress(intptr_t size_in_bytes);
+
+  void set_end_of_unswept_pages(Page* page) {
+    end_of_unswept_pages_ = page;
+  }
+
+  Page* end_of_unswept_pages() {
+    return end_of_unswept_pages_;
+  }
+
   Page* FirstPage() { return anchor_.next_page(); }
   Page* LastPage() { return anchor_.prev_page(); }
 
@@ -1935,6 +1949,11 @@ class PagedSpace : public Space {
   // sweeping is done conservatively.
   intptr_t unswept_free_bytes_;
 
+  // The sweeper threads iterate over the list of pointer and data space pages
+  // and sweep these pages concurrently. They will stop sweeping after the
+  // end_of_unswept_pages_ page.
+  Page* end_of_unswept_pages_;
+
   // Expands the space by allocating a fixed number of pages. Returns false if
   // it cannot allocate requested number of pages from OS, or if the hard heap
   // size limit has been hit.