Revision: 4849
Author: [email protected]
Date: Fri Jun 11 10:03:19 2010
Log: Faster implementation of Heap::RecordWrites.
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
http://code.google.com/p/v8/source/detail?r=4849
Modified:
/branches/bleeding_edge/src/heap-inl.h
/branches/bleeding_edge/src/spaces-inl.h
/branches/bleeding_edge/src/spaces.h
=======================================
--- /branches/bleeding_edge/src/heap-inl.h Tue Jun 8 02:35:47 2010
+++ /branches/bleeding_edge/src/heap-inl.h Fri Jun 11 10:03:19 2010
@@ -196,12 +196,9 @@
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));
}
=======================================
--- /branches/bleeding_edge/src/spaces-inl.h Thu May 27 05:30:45 2010
+++ /branches/bleeding_edge/src/spaces-inl.h Fri Jun 11 10:03:19 2010
@@ -150,6 +150,33 @@
uint32_t Page::GetRegionMaskForAddress(Address addr) {
return 1 << GetRegionNumberForAddress(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) {
=======================================
--- /branches/bleeding_edge/src/spaces.h Thu May 27 05:30:45 2010
+++ /branches/bleeding_edge/src/spaces.h Fri Jun 11 10:03:19 2010
@@ -220,6 +220,7 @@
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);
--
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