Extend the maximum size map space

On 32-bit the maps are now aligned on a 32-byte boundary in order to encode more maps during compacting GC. The actual size of a map on 32-bit is 28 bytes making this change waste 4 bytes per map.

On 64-bit the encoding for compacting GC is now using more than 32-bits and the maps here are still pointer size aligned. The actual size of a map on 64-bit is 48 bytes and this change does not intruduce any waste.

My choice of 16 bits for kMapPageIndexBits for 64-bit should give the same maximum number of pages (8K) for map space. As maps on 64-bit are larger than on 32-bit the total number of maps on 64-bit will be smaller than on 32-bit. We could consider raising this to 17 or 18.

I moved the kPageSizeBits to globals.h as the calculation of the encoding really depended on this.

There are still an #ifdef/#endif in objects.h and this constant could be moved to globaks.h as well, but I kept it together with the related constants.

All the tests run in debug mode with additional options --gc-global --always-compact as well (except for a few tests on which also fails before this change when run with --gc-global --always-compact).

BUG=http://code.google.com/p/v8/issues/detail?id=524
BUG=http://crbug.com/29428
TEST=test/mjsunit/regress/regress-524.js

Review URL: http://codereview.chromium.org/504026

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3481 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/globals.h

@@ -145,6 +145,14 @@ const intptr_t kObjectAlignmentMask = kObjectAlignment - 1;
 const intptr_t kPointerAlignment = (1 << kPointerSizeLog2);
 const intptr_t kPointerAlignmentMask = kPointerAlignment - 1;
 
+// Desired alignment for maps.
+#if V8_HOST_ARCH_64_BIT
+const intptr_t kMapAlignmentBits = kObjectAlignmentBits;
+#else
+const intptr_t kMapAlignmentBits = kObjectAlignmentBits + 3;
+#endif
+const intptr_t kMapAlignment = (1 << kMapAlignmentBits);
+const intptr_t kMapAlignmentMask = kMapAlignment - 1;
 
 // Tag information for Failure.
 const int kFailureTag = 3;
@@ -174,6 +182,11 @@ const Address kFromSpaceZapValue = reinterpret_cast<Address>(0xbeefdad);
 #endif
 
 
+// Number of bits to represent the page size for paged spaces. The value of 13
+// gives 8K bytes per page.
+const int kPageSizeBits = 13;
+
+
 // Constants relevant to double precision floating point numbers.
 
 // Quiet NaNs have bits 51 to 62 set, possibly the sign bit, and no
@@ -450,6 +463,10 @@ enum StateTag {
 #define POINTER_SIZE_ALIGN(value)                               \
   (((value) + kPointerAlignmentMask) & ~kPointerAlignmentMask)
 
+// MAP_SIZE_ALIGN returns the value aligned as a map pointer.
+#define MAP_SIZE_ALIGN(value)                               \
+  (((value) + kMapAlignmentMask) & ~kMapAlignmentMask)
+
 // The expression OFFSET_OF(type, field) computes the byte-offset
 // of the specified field relative to the containing type. This
 // corresponds to 'offsetof' (in stddef.h), except that it doesn't

src/heap-inl.h

@@ -129,6 +129,12 @@ Object* Heap::AllocateRawMap() {
 #endif
   Object* result = map_space_->AllocateRaw(Map::kSize);
   if (result->IsFailure()) old_gen_exhausted_ = true;
+#ifdef DEBUG
+  if (!result->IsFailure()) {
+    // Maps have their own alignment.
+    CHECK((OffsetFrom(result) & kMapAlignmentMask) == kHeapObjectTag);
+  }
+#endif
   return result;
 }
 

src/heap.cc

@@ -1142,6 +1142,13 @@ Object* Heap::AllocateMap(InstanceType instance_type, int instance_size) {
   map->set_unused_property_fields(0);
   map->set_bit_field(0);
   map->set_bit_field2(0);
+
+  // If the map object is aligned fill the padding area with Smi 0 objects.
+  if (Map::kPadStart < Map::kSize) {
+    memset(reinterpret_cast<byte*>(map) + Map::kPadStart - kHeapObjectTag,
+           0,
+           Map::kSize - Map::kPadStart);
+  }
   return map;
 }
 

src/heap.h

@@ -891,7 +891,7 @@ class Heap : public AllStatic {
   // The number of MapSpace pages is limited by the way we pack
   // Map pointers during GC.
   static const int kMaxMapSpaceSize =
-      (1 << MapWord::kMapPageIndexBits) * Page::kPageSize;
+      (1 << (MapWord::kMapPageIndexBits)) * Page::kPageSize;
 
 #if defined(V8_TARGET_ARCH_X64)
   static const int kMaxObjectSizeInNewSpace = 512*KB;

src/mark-compact.cc

@@ -836,11 +836,8 @@ void MarkCompactCollector::ClearNonLiveTransitions() {
 // space are encoded in their map pointer word (along with an encoding of
 // their map pointers).
 //
-//  31             21 20              10 9               0
-// +-----------------+------------------+-----------------+
-// |forwarding offset|page offset of map|page index of map|
-// +-----------------+------------------+-----------------+
-//  11 bits           11 bits            10 bits
+// The excact encoding is described in the comments for class MapWord in
+// objects.h.
 //
 // An address range [start, end) can have both live and non-live objects.
 // Maximal non-live regions are marked so they can be skipped on subsequent

src/objects-inl.h

@@ -952,14 +952,14 @@ MapWord MapWord::EncodeAddress(Address map_address, int offset) {
   // exceed the object area size of a page.
   ASSERT(0 <= offset && offset < Page::kObjectAreaSize);
 
-  int compact_offset = offset >> kObjectAlignmentBits;
+  uintptr_t compact_offset = offset >> kObjectAlignmentBits;
   ASSERT(compact_offset < (1 << kForwardingOffsetBits));
 
   Page* map_page = Page::FromAddress(map_address);
   ASSERT_MAP_PAGE_INDEX(map_page->mc_page_index);
 
-  int map_page_offset =
-      map_page->Offset(map_address) >> kObjectAlignmentBits;
+  uintptr_t map_page_offset =
+      map_page->Offset(map_address) >> kMapAlignmentBits;
 
   uintptr_t encoding =
       (compact_offset << kForwardingOffsetShift) |
@@ -975,8 +975,8 @@ Address MapWord::DecodeMapAddress(MapSpace* map_space) {
   ASSERT_MAP_PAGE_INDEX(map_page_index);
 
   int map_page_offset = static_cast<int>(
-      ((value_ & kMapPageOffsetMask) >> kMapPageOffsetShift)
-      << kObjectAlignmentBits);
+      ((value_ & kMapPageOffsetMask) >> kMapPageOffsetShift) <<
+      kMapAlignmentBits);
 
   return (map_space->PageAddress(map_page_index) + map_page_offset);
 }

src/objects.h

@@ -892,15 +892,25 @@ class MapWord BASE_EMBEDDED {
   static const int kOverflowBit = 1;  // overflow bit
   static const int kOverflowMask = (1 << kOverflowBit);  // overflow mask
 
-  // Forwarding pointers and map pointer encoding
-  //  31             21 20              10 9               0
+  // Forwarding pointers and map pointer encoding. On 32 bit all the bits are
+  // used.
   // +-----------------+------------------+-----------------+
   // |forwarding offset|page offset of map|page index of map|
   // +-----------------+------------------+-----------------+
-  //  11 bits           11 bits            10 bits
-  static const int kMapPageIndexBits = 10;
-  static const int kMapPageOffsetBits = 11;
-  static const int kForwardingOffsetBits = 11;
+  //          ^                 ^                  ^
+  //          |                 |                  |
+  //          |                 |          kMapPageIndexBits
+  //          |         kMapPageOffsetBits
+  // kForwardingOffsetBits
+  static const int kMapPageOffsetBits = kPageSizeBits - kMapAlignmentBits;
+  static const int kForwardingOffsetBits = kPageSizeBits - kObjectAlignmentBits;
+#ifdef V8_HOST_ARCH_64_BIT
+  static const int kMapPageIndexBits = 16;
+#else
+  // Use all the 32-bits to encode on a 32-bit platform.
+  static const int kMapPageIndexBits =
+      32 - (kMapPageOffsetBits + kForwardingOffsetBits);
+#endif
 
   static const int kMapPageIndexShift = 0;
   static const int kMapPageOffsetShift =
@@ -908,16 +918,12 @@ class MapWord BASE_EMBEDDED {
   static const int kForwardingOffsetShift =
       kMapPageOffsetShift + kMapPageOffsetBits;
 
-  // 0x000003FF
-  static const uint32_t kMapPageIndexMask =
+  // Bit masks covering the different parts the encoding.
+  static const uintptr_t kMapPageIndexMask =
       (1 << kMapPageOffsetShift) - 1;
-
-  // 0x001FFC00
-  static const uint32_t kMapPageOffsetMask =
+  static const uintptr_t kMapPageOffsetMask =
       ((1 << kForwardingOffsetShift) - 1) & ~kMapPageIndexMask;
-
-  // 0xFFE00000
-  static const uint32_t kForwardingOffsetMask =
+  static const uintptr_t kForwardingOffsetMask =
       ~(kMapPageIndexMask | kMapPageOffsetMask);
 
  private:
@@ -2841,7 +2847,6 @@ class Map: public HeapObject {
   // [stub cache]: contains stubs compiled for this map.
   DECL_ACCESSORS(code_cache, FixedArray)
 
-  // Returns a copy of the map.
   Object* CopyDropDescriptors();
 
   // Returns a copy of the map, with all transitions dropped from the
@@ -2909,7 +2914,8 @@ class Map: public HeapObject {
   static const int kInstanceDescriptorsOffset =
       kConstructorOffset + kPointerSize;
   static const int kCodeCacheOffset = kInstanceDescriptorsOffset + kPointerSize;
-  static const int kSize = kCodeCacheOffset + kPointerSize;
+  static const int kPadStart = kCodeCacheOffset + kPointerSize;
+  static const int kSize = MAP_SIZE_ALIGN(kPadStart);
 
   // Byte offsets within kInstanceSizesOffset.
   static const int kInstanceSizeOffset = kInstanceSizesOffset + 0;

src/serialize.cc

@@ -632,7 +632,7 @@ HeapObject* Deserializer::GetAddressFromStart(int space) {
     return HeapObject::FromAddress(pages_[space][0] + offset);
   }
   ASSERT(SpaceIsPaged(space));
-  int page_of_pointee = offset >> Page::kPageSizeBits;
+  int page_of_pointee = offset >> kPageSizeBits;
   Address object_address = pages_[space][page_of_pointee] +
                            (offset & Page::kPageAlignmentMask);
   return HeapObject::FromAddress(object_address);
@@ -972,8 +972,8 @@ void Serializer::SerializeObject(
     int offset = CurrentAllocationAddress(space) - address;
     bool from_start = true;
     if (SpaceIsPaged(space)) {
-      if ((CurrentAllocationAddress(space) >> Page::kPageSizeBits) ==
-          (address >> Page::kPageSizeBits)) {
+      if ((CurrentAllocationAddress(space) >> kPageSizeBits) ==
+          (address >> kPageSizeBits)) {
         from_start = false;
         address = offset;
       }

src/spaces.cc

@@ -398,7 +398,7 @@ static int PagesInChunk(Address start, size_t size) {
   // start+size.  Page::kPageSize is a power of two so we can divide by
   // shifting.
   return static_cast<int>((RoundDown(start + size, Page::kPageSize)
-      - RoundUp(start, Page::kPageSize)) >> Page::kPageSizeBits);
+      - RoundUp(start, Page::kPageSize)) >> kPageSizeBits);
 }
 
 
@@ -412,7 +412,7 @@ Page* MemoryAllocator::AllocatePages(int requested_pages, int* allocated_pages,
   if (size_ + static_cast<int>(chunk_size) > capacity_) {
     // Request as many pages as we can.
     chunk_size = capacity_ - size_;
-    requested_pages = static_cast<int>(chunk_size >> Page::kPageSizeBits);
+    requested_pages = static_cast<int>(chunk_size >> kPageSizeBits);
 
     if (requested_pages <= 0) return Page::FromAddress(NULL);
   }

src/spaces.h

@@ -65,20 +65,23 @@ namespace internal {
 
 // Some assertion macros used in the debugging mode.
 
-#define ASSERT_PAGE_ALIGNED(address)                  \
+#define ASSERT_PAGE_ALIGNED(address)                                           \
   ASSERT((OffsetFrom(address) & Page::kPageAlignmentMask) == 0)
 
-#define ASSERT_OBJECT_ALIGNED(address)                \
+#define ASSERT_OBJECT_ALIGNED(address)                                         \
   ASSERT((OffsetFrom(address) & kObjectAlignmentMask) == 0)
 
-#define ASSERT_OBJECT_SIZE(size)                      \
+#define ASSERT_MAP_ALIGNED(address)                                            \
+  ASSERT((OffsetFrom(address) & kMapAlignmentMask) == 0)
+
+#define ASSERT_OBJECT_SIZE(size)                                               \
   ASSERT((0 < size) && (size <= Page::kMaxHeapObjectSize))
 
-#define ASSERT_PAGE_OFFSET(offset)                    \
-  ASSERT((Page::kObjectStartOffset <= offset)         \
+#define ASSERT_PAGE_OFFSET(offset)                                             \
+  ASSERT((Page::kObjectStartOffset <= offset)                                  \
       && (offset <= Page::kPageSize))
 
-#define ASSERT_MAP_PAGE_INDEX(index)                            \
+#define ASSERT_MAP_PAGE_INDEX(index)                                           \
   ASSERT((0 <= index) && (index <= MapSpace::kMaxMapPageIndex))
 
 
@@ -106,11 +109,8 @@ class AllocationInfo;
 // For this reason we add an offset to get room for the Page data at the start.
 //
 // The mark-compact collector transforms a map pointer into a page index and a
-// page offset. The map space can have up to 1024 pages, and 8M bytes (1024 *
-// 8K) in total.  Because a map pointer is aligned to the pointer size (4
-// bytes), 11 bits are enough to encode the page offset. 21 bits (10 for the
-// page index + 11 for the offset in the page) are required to encode a map
-// pointer.
+// page offset. The excact encoding is described in the comments for
+// class MapWord in objects.h.
 //
 // The only way to get a page pointer is by calling factory methods:
 //   Page* p = Page::FromAddress(addr); or
@@ -212,9 +212,6 @@ class Page {
   static void set_rset_state(RSetState state) { rset_state_ = state; }
 #endif
 
-  // 8K bytes per page.
-  static const int kPageSizeBits = 13;
-
   // Page size in bytes.  This must be a multiple of the OS page size.
   static const int kPageSize = 1 << kPageSizeBits;
 
@@ -514,7 +511,7 @@ class MemoryAllocator : public AllStatic {
 #endif
 
   // Due to encoding limitation, we can only have 8K chunks.
-  static const int kMaxNofChunks = 1 << Page::kPageSizeBits;
+  static const int kMaxNofChunks = 1 << kPageSizeBits;
   // If a chunk has at least 16 pages, the maximum heap size is about
   // 8K * 8K * 16 = 1G bytes.
 #ifdef V8_TARGET_ARCH_X64

test/mjsunit/mjsunit.status

@@ -45,6 +45,8 @@ array-constructor: PASS || TIMEOUT
 # Very slow on ARM, contains no architecture dependent code.
 unicode-case-overoptimization: PASS, TIMEOUT if ($arch == arm)
 
+# Skip long running test in debug.
+regress/regress-524: PASS, SKIP if $mode == debug
 
 [ $arch == arm ]
 

test/mjsunit/regress/regress-524.js

+// Copyright 2009 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Test allocation of a large number of maps.
+
+var i = 500000
+var a = new Array(i)
+for (var j = 0; j < i; j++) { var o = {}; o.x = 42; delete o.x; a[j] = o; }