Reland r6578 without changing the order of pages in the PageSpace::pages_ list.

runtime/vm/pages.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/pages.h"
 
 #include "platform/assert.h"
 #include "vm/gc_marker.h"
 #include "vm/gc_sweeper.h"
 #include "vm/object.h"
@@ skipping 97 matching lines @@
 HeapPage* PageSpace::AllocateLargePage(intptr_t size) {
   intptr_t page_size = LargePageSizeFor(size);
   HeapPage* page = HeapPage::Allocate(page_size, is_executable_);
   page->set_next(large_pages_);
   large_pages_ = page;
   capacity_ += page_size;
   return page;
 }
 
 
+void PageSpace::FreePage(HeapPage* page, HeapPage* previous_page) {
+  capacity_ -= page->memory_->size();
+  // Remove the page from the list.
+  if (previous_page != NULL) {
+    previous_page->set_next(page->next());
+  } else {
+    pages_ = page->next();
+  }
+  if (page == pages_tail_) {
+    pages_tail_ = previous_page;
+  }
+  // TODO(iposva): Consider adding to a pool of empty pages.
+  page->Deallocate();
+}
+
+
 void PageSpace::FreeLargePage(HeapPage* page, HeapPage* previous_page) {
   capacity_ -= page->memory_->size();
   // Remove the page from the list.
   if (previous_page != NULL) {
     previous_page->set_next(page->next());
   } else {
     large_pages_ = page->next();
   }
   page->Deallocate();
 }
@@ skipping 149 matching lines @@
   GCMarker marker(heap_);
   marker.MarkObjects(isolate, this, invoke_api_callbacks);
 
   // Reset the bump allocation page to unused.
   bump_page_ = NULL;
   // Reset the freelists and setup sweeping.
   freelist_.Reset();
   GCSweeper sweeper(heap_);
   intptr_t in_use = 0;
 
+  HeapPage* prev_page = NULL;
   HeapPage* page = pages_;
   while (page != NULL) {
     intptr_t page_in_use = sweeper.SweepPage(page, &freelist_);
-    in_use += page_in_use;
-    page = page->next();
+    HeapPage* next_page = page->next();
+    if (page_in_use == 0) {
+      FreePage(page, prev_page);
+    } else {
+      in_use += page_in_use;
+      prev_page = page;
+    }
+    // Advance to the next page.
+    page = next_page;
   }
 
-  HeapPage* prev_page = NULL;
+  prev_page = NULL;
   page = large_pages_;
   while (page != NULL) {
     intptr_t page_in_use = sweeper.SweepLargePage(page);
     HeapPage* next_page = page->next();
     if (page_in_use == 0) {
       FreeLargePage(page, prev_page);
     } else {
       in_use += page_in_use;
       prev_page = page;
     }
@@ skipping 22 matching lines @@
     OS::PrintErr(" done.\n");
   }
 
   count_++;
   // Done, reset the marker.
   ASSERT(sweeping_);
   sweeping_ = false;
 }
 
 }  // namespace dart