Changeset 120568 in webkit for trunk/Source/JavaScriptCore/heap/MarkStack.cpp

Timestamp:

Jun 17, 2012, 9:35:21 PM (13 years ago)

Author:

[email protected]

Message:

GC copy phase spends needless cycles zero-filling blocks
​https://bugs.webkit.org/show_bug.cgi?id=89128

Reviewed by Gavin Barraclough.

We only need to zero-fill when we're allocating memory that might not
get fully initialized before GC.

• heap/CopiedBlock.h:

(JSC::CopiedBlock::createNoZeroFill):
(JSC::CopiedBlock::create): Added a way to create without zero-filling.
This is our optimization.

(JSC::CopiedBlock::zeroFillToEnd):
(JSC::CopiedBlock::CopiedBlock): Split zero-filling out from creation,
so we can sometimes create without zero-filling.

• heap/CopiedSpace.cpp:

(JSC::CopiedSpace::init):
(JSC::CopiedSpace::tryAllocateSlowCase):
(JSC::CopiedSpace::doneCopying): Renamed addNewBlock to allocateBlock()
to clarify that the new block is always newly-allocated.

(JSC::CopiedSpace::doneFillingBlock): Make sure to zero-fill to the end
of a block that might be used in the future for allocation. (Most of the
time, this is a no-op, since we've already filled the block completely.)

(JSC::CopiedSpace::getFreshBlock): Removed this function because the
abstraction of "allocation must succeed" is no longer useful.

• heap/CopiedSpace.h: Updated declarations to match.

• heap/CopiedSpaceInlineMethods.h:

(JSC::CopiedSpace::allocateBlockForCopyingPhase): New function, which
knows that it can skip zero-filling.

Added tighter scoping to our lock, to improve parallelism.

(JSC::CopiedSpace::allocateBlock): Folded getFreshBlock functionality
into this function, for simplicity.

• heap/MarkStack.cpp:

(JSC::SlotVisitor::startCopying):
(JSC::SlotVisitor::allocateNewSpace): Use our new zero-fill-free helper
function for great good.

File:

• trunk/Source/JavaScriptCore/heap/MarkStack.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/heap/MarkStack.cpp

@@ -496 +496 @@
 {
     ASSERT(!m_copyBlock);
-    if (!m_shared.m_copiedSpace->borrowBlock(&m_copyBlock))
-        CRASH();
+    m_copyBlock = m_shared.m_copiedSpace->allocateBlockForCopyingPhase();
 }    
 
@@ -518 +517 @@
         // call doneCopying() because this thread is considered active.
         m_shared.m_copiedSpace->doneFillingBlock(m_copyBlock);
-        if (!m_shared.m_copiedSpace->borrowBlock(&m_copyBlock))
-            CRASH();
+        m_copyBlock = m_shared.m_copiedSpace->allocateBlockForCopyingPhase();
     }
     return CopiedSpace::allocateFromBlock(m_copyBlock, bytes);