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Faster implementation of Heap::RecordWrites.

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Naive algorithm for to update RSets for a span is rather inefficient
as it performs many unnecessary operations (retrieving a mask, updating
it with the same bit as many pointers go into a single region).

Review URL: http://codereview.chromium.org/2727009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4849 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
antonm@chromium.org 2010-06-11 17:03:19 +00:00
parent 7e13119880
commit 1688876682
3 changed files with 31 additions and 6 deletions
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9
src/heap-inl.h
View File

@ -196,12 +196,9 @@ void Heap::RecordWrite(Address address, int offset) {
void Heap::RecordWrites(Address address, int start, int len) {
if (new_space_.Contains(address)) return;
ASSERT(!new_space_.FromSpaceContains(address));
for (int offset = start;
offset < start + len * kPointerSize;
offset += kPointerSize) {
SLOW_ASSERT(Contains(address + offset));
Page::FromAddress(address)->MarkRegionDirty(address + offset);
}
Page* page = Page::FromAddress(address);
page->SetRegionMarks(page->GetRegionMarks() |
page->GetRegionMaskForSpan(address + start, len * kPointerSize));
}

27
src/spaces-inl.h
View File

@ -152,6 +152,33 @@ uint32_t Page::GetRegionMaskForAddress(Address addr) {
}
uint32_t Page::GetRegionMaskForSpan(Address start, int length_in_bytes) {
uint32_t result = 0;
if (length_in_bytes >= kPageSize) {
result = kAllRegionsDirtyMarks;
} else if (length_in_bytes > 0) {
int start_region = GetRegionNumberForAddress(start);
int end_region =
GetRegionNumberForAddress(start + length_in_bytes - kPointerSize);
uint32_t start_mask = (~0) << start_region;
uint32_t end_mask = ~((~1) << end_region);
result = start_mask & end_mask;
// if end_region < start_region, the mask is ored.
if (result == 0) result = start_mask | end_mask;
}
#ifdef DEBUG
if (FLAG_enable_slow_asserts) {
uint32_t expected = 0;
for (Address a = start; a < start + length_in_bytes; a += kPointerSize) {
expected |= GetRegionMaskForAddress(a);
}
ASSERT(expected == result);
}
#endif
return result;
}
void Page::MarkRegionDirty(Address address) {
SetRegionMarks(GetRegionMarks() | GetRegionMaskForAddress(address));
}

1
src/spaces.h
View File

@ -220,6 +220,7 @@ class Page {
inline void SetRegionMarks(uint32_t dirty);
inline uint32_t GetRegionMaskForAddress(Address addr);
inline uint32_t GetRegionMaskForSpan(Address start, int length_in_bytes);
inline int GetRegionNumberForAddress(Address addr);
inline void MarkRegionDirty(Address addr);