[heap] Add page evacuation mode for new->new

src/heap/spaces.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/spaces.h"
 
 #include "src/base/bits.h"
 #include "src/base/platform/platform.h"
 #include "src/base/platform/semaphore.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 1368 matching lines @@
     DeleteArray(promoted_histogram_);
     promoted_histogram_ = NULL;
   }
 
   allocation_info_.Reset(nullptr, nullptr);
 
   to_space_.TearDown();
   from_space_.TearDown();
 }
 
-
 void NewSpace::Flip() { SemiSpace::Swap(&from_space_, &to_space_); }
 
 
 void NewSpace::Grow() {
   // Double the semispace size but only up to maximum capacity.
   DCHECK(TotalCapacity() < MaximumCapacity());
   int new_capacity =
       Min(MaximumCapacity(),
           FLAG_semi_space_growth_factor * static_cast<int>(TotalCapacity()));
   if (to_space_.GrowTo(new_capacity)) {
@@ skipping 25 matching lines @@
       if (!to_space_.GrowTo(from_space_.current_capacity())) {
         // We are in an inconsistent state because we could not
         // commit/uncommit memory from new space.
         CHECK(false);
       }
     }
   }
   DCHECK_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
 }
 
+bool NewSpace::Rebalance() {
+  CHECK(heap()->promotion_queue()->is_empty());
+  // Order here is important to make use of the page pool.
+  return to_space_.EnsureCurrentCapacity() &&
+         from_space_.EnsureCurrentCapacity();
+}
+
+bool SemiSpace::EnsureCurrentCapacity() {
+  if (is_committed()) {
+    const int expected_pages = current_capacity_ / Page::kPageSize;
+    int actual_pages = 0;
+    Page* current_page = anchor()->next_page();
+    while (current_page != anchor()) {
+      actual_pages++;
+      current_page = current_page->next_page();
+      if (actual_pages > expected_pages) {
+        Page* to_remove = current_page->prev_page();
+        to_remove->Unlink();

[ulan, 2016/06/14 15:38:51]

Please add dcheck that we discussed offline.

[Michael Lippautz, 2016/06/15 06:49:30]

Done.

+        heap()->memory_allocator()->Free<MemoryAllocator::kPooledAndQueue>(
+            to_remove);
+      }
+    }
+    while (actual_pages < expected_pages) {
+      actual_pages++;
+      current_page =
+          heap()->memory_allocator()->AllocatePage<MemoryAllocator::kPooled>(
+              Page::kAllocatableMemory, this, executable());
+      if (current_page == nullptr) return false;
+      DCHECK_NOT_NULL(current_page);
+      current_page->InsertAfter(anchor());
+      Bitmap::Clear(current_page);
+      current_page->SetFlags(anchor()->prev_page()->GetFlags(),
+                             Page::kCopyAllFlags);
+      heap()->CreateFillerObjectAt(current_page->area_start(),
+                                   current_page->area_size(),
+                                   ClearRecordedSlots::kNo);
+    }
+  }
+  return true;
+}
 
 void LocalAllocationBuffer::Close() {
   if (IsValid()) {
     heap_->CreateFillerObjectAt(
         allocation_info_.top(),
         static_cast<int>(allocation_info_.limit() - allocation_info_.top()),
         ClearRecordedSlots::kNo);
   }
 }
 
@@ skipping 422 matching lines @@
            page->IsFlagSet(MemoryChunk::IN_FROM_SPACE));
   }
 }
 
 
 void SemiSpace::Reset() {
   DCHECK_NE(anchor_.next_page(), &anchor_);
   current_page_ = anchor_.next_page();
 }
 
-bool SemiSpace::ReplaceWithEmptyPage(Page* old_page) {
-  // TODO(mlippautz): We do not have to get a new page here when the semispace
-  // is uncommitted later on.
-  Page* new_page = heap()->memory_allocator()->AllocatePage(
-      Page::kAllocatableMemory, this, executable());
-  if (new_page == nullptr) return false;
-  Bitmap::Clear(new_page);
-  new_page->SetFlags(old_page->GetFlags(), Page::kCopyAllFlags);
-  new_page->set_next_page(old_page->next_page());
-  new_page->set_prev_page(old_page->prev_page());
-  old_page->next_page()->set_prev_page(new_page);
-  old_page->prev_page()->set_next_page(new_page);
-  heap()->CreateFillerObjectAt(new_page->area_start(), new_page->area_size(),
-                               ClearRecordedSlots::kNo);
-  return true;
+void SemiSpace::RemovePage(Page* page) {
+  if (current_page_ == page) {
+    current_page_ = page->prev_page();
+  }
+  page->Unlink();
+}
+
+void SemiSpace::PrependPage(Page* page) {
+  page->SetFlags(current_page()->GetFlags(), Page::kCopyAllFlags);
+  page->set_owner(this);
+  page->InsertAfter(anchor());
 }
 
 void SemiSpace::Swap(SemiSpace* from, SemiSpace* to) {
   // We won't be swapping semispaces without data in them.
   DCHECK_NE(from->anchor_.next_page(), &from->anchor_);
   DCHECK_NE(to->anchor_.next_page(), &to->anchor_);
 
   intptr_t saved_to_space_flags = to->current_page()->GetFlags();
 
   // We swap all properties but id_.
@@ skipping 1318 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 }  // namespace internal
 }  // namespace v8