Revision: 19332
Author: [email protected]
Date: Wed Feb 12 15:40:23 2014 UTC
Log: Make prev and next pointer in pages list AtomicWords and access
them using acquire/release semantics.
BUG=
[email protected]
Review URL: https://codereview.chromium.org/150413009
http://code.google.com/p/v8/source/detail?r=19332
Modified:
/branches/bleeding_edge/src/spaces.cc
/branches/bleeding_edge/src/spaces.h
=======================================
--- /branches/bleeding_edge/src/spaces.cc Tue Jan 21 19:30:27 2014 UTC
+++ /branches/bleeding_edge/src/spaces.cc Wed Feb 12 15:40:23 2014 UTC
@@ -560,21 +560,12 @@
void MemoryChunk::InsertAfter(MemoryChunk* other) {
- next_chunk_ = other->next_chunk_;
- prev_chunk_ = other;
+ MemoryChunk* other_next = other->next_chunk();
- // This memory barrier is needed since concurrent sweeper threads may
iterate
- // over the list of pages while a new page is inserted.
- // TODO(hpayer): find a cleaner way to guarantee that the page list can
be
- // expanded concurrently
- MemoryBarrier();
-
- // The following two write operations can take effect in arbitrary order
- // since pages are always iterated by the sweeper threads in LIFO order,
i.e,
- // the inserted page becomes visible for the sweeper threads after
- // other->next_chunk_ = this;
- other->next_chunk_->prev_chunk_ = this;
- other->next_chunk_ = this;
+ set_next_chunk(other_next);
+ set_prev_chunk(other);
+ other_next->set_prev_chunk(this);
+ other->set_next_chunk(this);
}
@@ -583,10 +574,12 @@
heap_->decrement_scan_on_scavenge_pages();
ClearFlag(SCAN_ON_SCAVENGE);
}
- next_chunk_->prev_chunk_ = prev_chunk_;
- prev_chunk_->next_chunk_ = next_chunk_;
- prev_chunk_ = NULL;
- next_chunk_ = NULL;
+ MemoryChunk* next_element = next_chunk();
+ MemoryChunk* prev_element = prev_chunk();
+ next_element->set_prev_chunk(prev_element);
+ prev_element->set_next_chunk(next_element);
+ set_prev_chunk(NULL);
+ set_next_chunk(NULL);
}
=======================================
--- /branches/bleeding_edge/src/spaces.h Mon Feb 3 12:20:15 2014 UTC
+++ /branches/bleeding_edge/src/spaces.h Wed Feb 12 15:40:23 2014 UTC
@@ -313,11 +313,21 @@
bool is_valid() { return address() != NULL; }
- MemoryChunk* next_chunk() const { return next_chunk_; }
- MemoryChunk* prev_chunk() const { return prev_chunk_; }
+ MemoryChunk* next_chunk() const {
+ return reinterpret_cast<MemoryChunk*>(Acquire_Load(&next_chunk_));
+ }
- void set_next_chunk(MemoryChunk* next) { next_chunk_ = next; }
- void set_prev_chunk(MemoryChunk* prev) { prev_chunk_ = prev; }
+ MemoryChunk* prev_chunk() const {
+ return reinterpret_cast<MemoryChunk*>(Acquire_Load(&prev_chunk_));
+ }
+
+ void set_next_chunk(MemoryChunk* next) {
+ Release_Store(&next_chunk_, reinterpret_cast<AtomicWord>(next));
+ }
+
+ void set_prev_chunk(MemoryChunk* prev) {
+ Release_Store(&prev_chunk_, reinterpret_cast<AtomicWord>(prev));
+ }
Space* owner() const {
if ((reinterpret_cast<intptr_t>(owner_) & kFailureTagMask) ==
@@ -536,7 +546,7 @@
static const intptr_t kAlignmentMask = kAlignment - 1;
- static const intptr_t kSizeOffset = kPointerSize + kPointerSize;
+ static const intptr_t kSizeOffset = 0;
static const intptr_t kLiveBytesOffset =
kSizeOffset + kPointerSize + kPointerSize + kPointerSize +
@@ -550,7 +560,8 @@
static const size_t kHeaderSize = kWriteBarrierCounterOffset +
kPointerSize +
kIntSize + kIntSize + kPointerSize +
- 5 * kPointerSize;
+ 5 * kPointerSize +
+ kPointerSize + kPointerSize;
static const int kBodyOffset =
CODE_POINTER_ALIGN(kHeaderSize + Bitmap::kSize);
@@ -622,7 +633,7 @@
inline Heap* heap() { return heap_; }
- static const int kFlagsOffset = kPointerSize * 3;
+ static const int kFlagsOffset = kPointerSize;
bool IsEvacuationCandidate() { return IsFlagSet(EVACUATION_CANDIDATE); }
@@ -671,8 +682,6 @@
static inline void UpdateHighWaterMark(Address mark);
protected:
- MemoryChunk* next_chunk_;
- MemoryChunk* prev_chunk_;
size_t size_;
intptr_t flags_;
@@ -719,6 +728,12 @@
Executability executable,
Space* owner);
+ private:
+ // next_chunk_ holds a pointer of type MemoryChunk
+ AtomicWord next_chunk_;
+ // prev_chunk_ holds a pointer of type MemoryChunk
+ AtomicWord prev_chunk_;
+
friend class MemoryAllocator;
};
--
--
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