- Do not bump allocate in old-space pages. Always use

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 13 matching lines @@
             "Print free list statistics after a GC");
 
 HeapPage* HeapPage::Initialize(VirtualMemory* memory, bool is_executable) {
   ASSERT(memory->size() > VirtualMemory::PageSize());
   memory->Commit(is_executable);
 
   HeapPage* result = reinterpret_cast<HeapPage*>(memory->address());
   result->memory_ = memory;
   result->next_ = NULL;
   result->used_ = 0;
-  result->top_ = result->first_object_start();
   return result;
 }
 
 
 HeapPage* HeapPage::Allocate(intptr_t size, bool is_executable) {
   VirtualMemory* memory =
       VirtualMemory::ReserveAligned(size, PageSpace::kPageAlignment);
   return Initialize(memory, is_executable);
 }
 
 
 void HeapPage::Deallocate() {
   // The memory for this object will become unavailable after the delete below.
   delete memory_;
 }
 
 
 void HeapPage::VisitObjects(ObjectVisitor* visitor) const {
-  uword obj_addr = first_object_start();
-  uword end_addr = top();
+  uword obj_addr = object_start();
+  uword end_addr = object_end();
   while (obj_addr < end_addr) {
     RawObject* raw_obj = RawObject::FromAddr(obj_addr);
     visitor->VisitObject(raw_obj);
     obj_addr += raw_obj->Size();
   }
   ASSERT(obj_addr == end_addr);
 }
 
 
 void HeapPage::VisitObjectPointers(ObjectPointerVisitor* visitor) const {
-  uword obj_addr = first_object_start();
-  uword end_addr = top();
+  uword obj_addr = object_start();
+  uword end_addr = object_end();
   while (obj_addr < end_addr) {
     RawObject* raw_obj = RawObject::FromAddr(obj_addr);
     obj_addr += raw_obj->VisitPointers(visitor);
   }
   ASSERT(obj_addr == end_addr);
 }
 
 
 RawObject* HeapPage::FindObject(FindObjectVisitor* visitor) const {
-  uword obj_addr = first_object_start();
-  uword end_addr = top();
+  uword obj_addr = object_start();
+  uword end_addr = object_end();
   while (obj_addr < end_addr) {
     RawObject* raw_obj = RawObject::FromAddr(obj_addr);
     if (raw_obj->FindObject(visitor)) {
       return raw_obj;  // Found object, return it.
     }
     obj_addr += raw_obj->Size();
   }
   ASSERT(obj_addr == end_addr);
   return Object::null();
 }
 
 
 void HeapPage::WriteProtect(bool read_only) {
   memory_->Protect(
       read_only ? VirtualMemory::kReadOnly : VirtualMemory::kReadWrite);
 }
 
 
 PageSpace::PageSpace(Heap* heap, intptr_t max_capacity, bool is_executable)
     : freelist_(),
       heap_(heap),
       pages_(NULL),
       pages_tail_(NULL),
       large_pages_(NULL),
-      bump_page_(NULL),
       max_capacity_(max_capacity),
       capacity_(0),
       in_use_(0),
       count_(0),
       is_executable_(is_executable),
       sweeping_(false),
       page_space_controller_(FLAG_heap_growth_space_ratio,
                              FLAG_heap_growth_rate,
                              FLAG_heap_growth_time_ratio) {
 }
 
 
 PageSpace::~PageSpace() {
   FreePages(pages_);
   FreePages(large_pages_);
 }
 
 
 intptr_t PageSpace::LargePageSizeFor(intptr_t size) {
   intptr_t page_size = Utils::RoundUp(size + sizeof(HeapPage),
                                       VirtualMemory::PageSize());
   return page_size;
 }
 
 
-void PageSpace::AllocatePage() {
+HeapPage* PageSpace::AllocatePage() {
   HeapPage* page = HeapPage::Allocate(kPageSize, is_executable_);
   if (pages_ == NULL) {
     pages_ = page;
   } else {
     pages_tail_->set_next(page);
   }
   pages_tail_ = page;
-  bump_page_ = NULL;  // Reenable scanning of pages for bump allocation.
   capacity_ += kPageSize;
+  page->set_object_end(page->memory_->end());
+  return page;
 }
 
 
 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;
+  // Only one object in this page.
+  page->set_object_end(page->object_start() + 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 {
@@ skipping 22 matching lines @@
 void PageSpace::FreePages(HeapPage* pages) {
   HeapPage* page = pages;
   while (page != NULL) {
     HeapPage* next = page->next();
     page->Deallocate();
     page = next;
   }
 }
 
 
-uword PageSpace::TryBumpAllocate(intptr_t size) {
-  if (pages_tail_ == NULL) {
-    return 0;
-  }
-  uword result = pages_tail_->TryBumpAllocate(size);
-  if (result != 0) {
-    return result;
-  }
-  if (bump_page_ == NULL) {
-    // The bump page has not yet been used: Start at the beginning of the list.
-    bump_page_ = pages_;
-  }
-  // The last page has already been attempted above.
-  while (bump_page_ != pages_tail_) {
-    ASSERT(bump_page_->next() != NULL);
-    result = bump_page_->TryBumpAllocate(size);
-    if (result != 0) {
-      return result;
-    }
-    bump_page_ = bump_page_->next();
-  }
-  // Ran through all of the pages trying to bump allocate: Give up.
-  return 0;
-}
-
-
 uword PageSpace::TryAllocate(intptr_t size) {
   return TryAllocate(size, kControlGrowth);
 }
 
 
 uword PageSpace::TryAllocate(intptr_t size, GrowthPolicy growth_policy) {
   ASSERT(size >= kObjectAlignment);
   ASSERT(Utils::IsAligned(size, kObjectAlignment));
   uword result = 0;
   if (size < kAllocatablePageSize) {
     result = freelist_.TryAllocate(size);
-    if (result == 0) {
-      result = TryBumpAllocate(size);
-      if ((result == 0) &&
-          (page_space_controller_.CanGrowPageSpace(size) ||
-           growth_policy == kForceGrowth) &&
-          CanIncreaseCapacity(kPageSize)) {
-        AllocatePage();
-        result = TryBumpAllocate(size);
-        ASSERT(result != 0);
-      }
+    if ((result == 0) &&
+        (page_space_controller_.CanGrowPageSpace(size) ||
+         growth_policy == kForceGrowth) &&
+        CanIncreaseCapacity(kPageSize)) {
+      HeapPage* page = AllocatePage();
+      ASSERT(page != NULL);
+      // Start of the newly allocated page is the allocated object.
+      result = page->object_start();
+      // Enqueue the remainder in the free list.
+      uword free_start = result + size;
+      freelist_.Free(free_start, page->object_end() - free_start);
     }
   } else {
     // Large page allocation.
     intptr_t page_size = LargePageSizeFor(size);
     if (page_size < size) {
       // On overflow we fail to allocate.
       return 0;
     }
     if (CanIncreaseCapacity(page_size)) {
       HeapPage* page = AllocateLargePage(size);
       if (page != NULL) {
-        result = page->top();
-        page->set_top(result + size);
+        result = page->object_start();
       }
     }
   }
   if (result != 0) {
     in_use_ += size;
   }
+  ASSERT((result & kObjectAlignmentMask) == kOldObjectAlignmentOffset);
   return result;
 }
 
 
 bool PageSpace::Contains(uword addr) const {
   HeapPage* page = pages_;
   while (page != NULL) {
     if (page->Contains(addr)) {
       return true;
     }
     page = page->next();
   }
 
   page = large_pages_;
   while (page != NULL) {
     if (page->Contains(addr)) {
       return true;
     }
     page = page->next();
   }
   return false;
 }
 
 
 void PageSpace::StartEndAddress(uword* start, uword* end) const {
   ASSERT(pages_ != NULL || large_pages_ != NULL);
   *start = static_cast<uword>(~0);
   *end = 0;
   for (HeapPage* page = pages_; page != NULL; page = page->next()) {
-    *start = Utils::Minimum(*start, page->start());
-    *end = Utils::Maximum(*end, page->end());
+    *start = Utils::Minimum(*start, page->object_start());
+    *end = Utils::Maximum(*end, page->object_end());
   }
   for (HeapPage* page = large_pages_; page != NULL; page = page->next()) {
-    *start = Utils::Minimum(*start, page->start());
-    *end = Utils::Maximum(*end, page->end());
+    *start = Utils::Minimum(*start, page->object_start());
+    *end = Utils::Maximum(*end, page->object_end());
   }
   ASSERT(*start != static_cast<uword>(~0));
   ASSERT(*end != 0);
 }
 
 
 void PageSpace::VisitObjects(ObjectVisitor* visitor) const {
   HeapPage* page = pages_;
   while (page != NULL) {
     page->VisitObjects(visitor);
@@ skipping 102 matching lines @@
   }
   Timer timer(true, "MarkSweep");
   timer.Start();
   int64_t start = OS::GetCurrentTimeMillis();
 
   // Mark all reachable old-gen objects.
   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_);
     HeapPage* next_page = page->next();
@@ skipping 178 matching lines @@
     return 0;
   } else {
     ASSERT(total_time >= gc_time);
     int result= static_cast<int>((static_cast<double>(gc_time) /
                              static_cast<double>(total_time)) * 100);
     return result;
   }
 }
 
 }  // namespace dart