X64: Move remembered set to a safe location on x64 platform.
Review URL: http://codereview.chromium.org/151148 git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2331 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
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@ -93,17 +93,21 @@ Address Page::AllocationTop() {
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void Page::ClearRSet() {
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#ifndef V8_HOST_ARCH_64_BIT
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// This method can be called in all rset states.
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memset(RSetStart(), 0, kRSetEndOffset - kRSetStartOffset);
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#endif
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}
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// Give an address a (32-bits):
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// Given a 32-bit address, separate its bits into:
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// | page address | words (6) | bit offset (5) | pointer alignment (2) |
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// The rset address is computed as:
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// The address of the rset word containing the bit for this word is computed as:
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// page_address + words * 4
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// For a 64-bit address, if it is:
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// | page address | quadwords(5) | bit offset(5) | pointer alignment (3) |
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// The address of the rset word containing the bit for this word is computed as:
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// page_address + quadwords * 4 + kRSetOffset.
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// The rset is accessed as 32-bit words, and bit offsets in a 32-bit word,
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// even on the X64 architecture.
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Address Page::ComputeRSetBitPosition(Address address, int offset,
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uint32_t* bitmask) {
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@ -115,7 +119,7 @@ Address Page::ComputeRSetBitPosition(Address address, int offset,
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*bitmask = 1 << (bit_offset % kBitsPerInt);
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Address rset_address =
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page->address() + (bit_offset / kBitsPerInt) * kIntSize;
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page->address() + kRSetOffset + (bit_offset / kBitsPerInt) * kIntSize;
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// The remembered set address is either in the normal remembered set range
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// of a page or else we have a large object page.
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ASSERT((page->RSetStart() <= rset_address && rset_address < page->RSetEnd())
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@ -131,8 +135,10 @@ Address Page::ComputeRSetBitPosition(Address address, int offset,
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// of the object:
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// (rset_address - page->ObjectAreaStart()).
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// Ie, we can just add the object size.
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// In the X64 architecture, the remembered set ends before the object start,
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// so we need to add an additional offset, from rset end to object start
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ASSERT(HeapObject::FromAddress(address)->IsFixedArray());
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rset_address +=
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rset_address += kObjectStartOffset - kRSetEndOffset +
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FixedArray::SizeFor(Memory::int_at(page->ObjectAreaStart()
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+ Array::kLengthOffset));
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}
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@ -160,14 +166,9 @@ void Page::UnsetRSet(Address address, int offset) {
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bool Page::IsRSetSet(Address address, int offset) {
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#ifdef V8_HOST_ARCH_64_BIT
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// TODO(X64): Reenable when RSet works.
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return true;
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#else // V8_HOST_ARCH_64_BIT
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uint32_t bitmask = 0;
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Address rset_address = ComputeRSetBitPosition(address, offset, &bitmask);
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return (Memory::uint32_at(rset_address) & bitmask) != 0;
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#endif // V8_HOST_ARCH_64_BIT
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}
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19
src/spaces.h
19
src/spaces.h
@ -93,13 +93,14 @@ class AllocationInfo;
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// bytes are used as remembered set, and the rest of the page is the object
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// area.
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//
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// Pointers are aligned to the pointer size (4 bytes), only 1 bit is needed
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// Pointers are aligned to the pointer size (4), only 1 bit is needed
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// for a pointer in the remembered set. Given an address, its remembered set
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// bit position (offset from the start of the page) is calculated by dividing
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// its page offset by 32. Therefore, the object area in a page starts at the
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// 256th byte (8K/32). Bytes 0 to 255 do not need the remembered set, so that
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// the first two words (64 bits) in a page can be used for other purposes.
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// TODO(X64): This description only represents the 32-bit layout.
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// On the 64-bit platform, we add an offset to the start of the remembered set.
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//
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// The mark-compact collector transforms a map pointer into a page index and a
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// page offset. The map space can have up to 1024 pages, and 8M bytes (1024 *
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@ -217,16 +218,24 @@ class Page {
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// Page size mask.
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static const intptr_t kPageAlignmentMask = (1 << kPageSizeBits) - 1;
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// The offset of the remembered set in a page, in addition to the empty words
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// formed as the remembered bits of the remembered set itself.
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#ifdef V8_TARGET_ARCH_X64
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static const int kRSetOffset = 4 * kPointerSize; // Room for four pointers.
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#else
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static const int kRSetOffset = 0;
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#endif
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// The end offset of the remembered set in a page
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// (heaps are aligned to pointer size).
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static const int kRSetEndOffset= kPageSize / kBitsPerPointer;
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// The start offset of the remembered set in a page.
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static const int kRSetStartOffset = kRSetEndOffset / kBitsPerPointer;
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static const int kRSetEndOffset = kRSetOffset + kPageSize / kBitsPerPointer;
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// The start offset of the object area in a page.
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static const int kObjectStartOffset = kRSetEndOffset;
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// The start offset of the remembered set in a page.
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static const int kRSetStartOffset = kRSetOffset +
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kObjectStartOffset / kBitsPerPointer;
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// Object area size in bytes.
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static const int kObjectAreaSize = kPageSize - kObjectStartOffset;
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