Shrink new space on compacting collections.

src/spaces.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 933 matching lines @@
 #endif
 
 
 void NewSpace::Flip() {
   SemiSpace tmp = from_space_;
   from_space_ = to_space_;
   to_space_ = tmp;
 }
 
 
-bool NewSpace::Grow() {
+void NewSpace::Grow() {
   ASSERT(Capacity() < MaximumCapacity());
-  // TODO(1240712): Failure to double the from space can result in
-  // semispaces of different sizes.  In the event of that failure, the
-  // to space doubling should be rolled back before returning false.
-  if (!to_space_.Grow() || !from_space_.Grow()) return false;
+  if (to_space_.Grow()) {
+    // Only grow from space if we managed to grow to space.
+    if (!from_space_.Grow()) {
+      // If we managed to grow to space but couldn't grow from space,
+      // attempt to shrink to space.
+      if (!to_space_.ShrinkTo(from_space_.Capacity())) {
+        // We are in an inconsistent state because we could not
+        // commit/uncommit memory from new space.
+        V8::FatalProcessOutOfMemory("Failed to grow new space.");
+      }
+    }
+  }
   allocation_info_.limit = to_space_.high();
   ASSERT_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
-  return true;
+}
+
+
+void NewSpace::Shrink() {
+  int new_capacity = Max(InitialCapacity(), 2 * Size());
+  int rounded_new_capacity = RoundUp(new_capacity, OS::AllocateAlignment());
+  if (rounded_new_capacity < Capacity() &&
+      to_space_.ShrinkTo(rounded_new_capacity))  {
+    // Only shrink from space if we managed to shrink to space.
+    if (!from_space_.ShrinkTo(rounded_new_capacity)) {
+      // If we managed to shrink to space but couldn't shrink from
+      // space, attempt to grow to space again.
+      if (!to_space_.GrowTo(from_space_.Capacity())) {
+        // We are in an inconsistent state because we could not
+        // commit/uncommit memory from new space.
+        V8::FatalProcessOutOfMemory("Failed to shrink new space.");
+      }
+    }
+  }
+  allocation_info_.limit = to_space_.high();
+  ASSERT_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
 }
 
 
 void NewSpace::ResetAllocationInfo() {
   allocation_info_.top = to_space_.low();
   allocation_info_.limit = to_space_.high();
   ASSERT_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
 }
 
 
@@ skipping 78 matching lines @@
 
 bool SemiSpace::Setup(Address start,
                       int initial_capacity,
                       int maximum_capacity) {
   // Creates a space in the young generation. The constructor does not
   // allocate memory from the OS.  A SemiSpace is given a contiguous chunk of
   // memory of size 'capacity' when set up, and does not grow or shrink
   // otherwise.  In the mark-compact collector, the memory region of the from
   // space is used as the marking stack. It requires contiguous memory
   // addresses.
+  initial_capacity_ = initial_capacity;
   capacity_ = initial_capacity;
   maximum_capacity_ = maximum_capacity;
   committed_ = false;
 
   start_ = start;
   address_mask_ = ~(maximum_capacity - 1);
   object_mask_ = address_mask_ | kHeapObjectTag;
   object_expected_ = reinterpret_cast<uintptr_t>(start) | kHeapObjectTag;
   age_mark_ = start_;
 
@@ skipping 13 matching lines @@
   int extra = Min(RoundUp(capacity_, OS::AllocateAlignment()),
                   maximum_extra);
   if (!MemoryAllocator::CommitBlock(high(), extra, executable())) {
     return false;
   }
   capacity_ += extra;
   return true;
 }
 
 
+bool SemiSpace::GrowTo(int new_capacity) {
+  ASSERT(new_capacity <= maximum_capacity_);
+  ASSERT(new_capacity > capacity_);
+  int delta = new_capacity - capacity_;
+  if (!MemoryAllocator::CommitBlock(high(), delta, executable())) {
+    return false;
+  }
+  capacity_ = new_capacity;
+  return true;
+}
+
+
+bool SemiSpace::ShrinkTo(int new_capacity) {
+  ASSERT(new_capacity >= initial_capacity_);
+  ASSERT(new_capacity < capacity_);
+  int delta = capacity_ - new_capacity;
+  if (!MemoryAllocator::UncommitBlock(high() - delta, delta)) {
+    return false;
+  }
+  capacity_ = new_capacity;
+  return true;
+}
+
+
 #ifdef DEBUG
 void SemiSpace::Print() { }
 
 
 void SemiSpace::Verify() { }
 #endif
 
 
 // -----------------------------------------------------------------------------
 // SemiSpaceIterator implementation.
@@ skipping 1497 matching lines @@
                      reinterpret_cast<Object**>(object->address()
                                                 + Page::kObjectAreaSize),
                      allocation_top);
       PrintF("\n");
     }
   }
 }
 #endif  // DEBUG
 
 } }  // namespace v8::internal