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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/182878">182878</a></dd>
<dt>Author</dt> <dd>akling@apple.com</dd>
<dt>Date</dt> <dd>2015-04-15 20:40:14 -0700 (Wed, 15 Apr 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>Make MarkedBlock and WeakBlock 4x smaller.
<https://webkit.org/b/143802>
Reviewed by Mark Hahnenberg.
To reduce GC heap fragmentation and generally use less memory, reduce the size of MarkedBlock
and its buddy WeakBlock by 4x, bringing them from 64kB+4kB to 16kB+1kB.
In a sampling of cool web sites, I'm seeing ~8% average reduction in overall GC heap size.
Some examples:
apple.com: 6.3MB -> 5.5MB (14.5% smaller)
reddit.com: 4.5MB -> 4.1MB ( 9.7% smaller)
twitter.com: 23.2MB -> 21.4MB ( 8.4% smaller)
cuteoverload.com: 24.5MB -> 23.6MB ( 3.8% smaller)
Benchmarks look mostly neutral.
Some small slowdowns on Octane, some slightly bigger speedups on Kraken and SunSpider.
* heap/MarkedBlock.h:
* heap/WeakBlock.h:
* llint/LLIntData.cpp:
(JSC::LLInt::Data::performAssertions):
* llint/LowLevelInterpreter.asm:</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreheapMarkedBlockh">trunk/Source/JavaScriptCore/heap/MarkedBlock.h</a></li>
<li><a href="#trunkSourceJavaScriptCoreheapWeakBlockh">trunk/Source/JavaScriptCore/heap/WeakBlock.h</a></li>
<li><a href="#trunkSourceJavaScriptCorellintLLIntDatacpp">trunk/Source/JavaScriptCore/llint/LLIntData.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCorellintLowLevelInterpreterasm">trunk/Source/JavaScriptCore/llint/LowLevelInterpreter.asm</a></li>
</ul>
</div>
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<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (182877 => 182878)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2015-04-16 02:53:44 UTC (rev 182877)
+++ trunk/Source/JavaScriptCore/ChangeLog 2015-04-16 03:40:14 UTC (rev 182878)
</span><span class="lines">@@ -1,3 +1,30 @@
</span><ins>+2015-04-15 Andreas Kling <akling@apple.com>
+
+ Make MarkedBlock and WeakBlock 4x smaller.
+ <https://webkit.org/b/143802>
+
+ Reviewed by Mark Hahnenberg.
+
+ To reduce GC heap fragmentation and generally use less memory, reduce the size of MarkedBlock
+ and its buddy WeakBlock by 4x, bringing them from 64kB+4kB to 16kB+1kB.
+
+ In a sampling of cool web sites, I'm seeing ~8% average reduction in overall GC heap size.
+ Some examples:
+
+ apple.com: 6.3MB -> 5.5MB (14.5% smaller)
+ reddit.com: 4.5MB -> 4.1MB ( 9.7% smaller)
+ twitter.com: 23.2MB -> 21.4MB ( 8.4% smaller)
+ cuteoverload.com: 24.5MB -> 23.6MB ( 3.8% smaller)
+
+ Benchmarks look mostly neutral.
+ Some small slowdowns on Octane, some slightly bigger speedups on Kraken and SunSpider.
+
+ * heap/MarkedBlock.h:
+ * heap/WeakBlock.h:
+ * llint/LLIntData.cpp:
+ (JSC::LLInt::Data::performAssertions):
+ * llint/LowLevelInterpreter.asm:
+
</ins><span class="cx"> 2015-04-15 Jordan Harband <ljharb@gmail.com>
</span><span class="cx">
</span><span class="cx"> String.prototype.startsWith/endsWith/includes have wrong length in r182673
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreheapMarkedBlockh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/heap/MarkedBlock.h (182877 => 182878)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/heap/MarkedBlock.h 2015-04-16 02:53:44 UTC (rev 182877)
+++ trunk/Source/JavaScriptCore/heap/MarkedBlock.h 2015-04-16 03:40:14 UTC (rev 182878)
</span><span class="lines">@@ -74,7 +74,7 @@
</span><span class="cx"> public:
</span><span class="cx"> static const size_t atomSize = 16; // bytes
</span><span class="cx"> static const size_t atomShiftAmount = 4; // log_2(atomSize) FIXME: Change atomSize to 16.
</span><del>- static const size_t blockSize = 64 * KB;
</del><ins>+ static const size_t blockSize = 16 * KB;
</ins><span class="cx"> static const size_t blockMask = ~(blockSize - 1); // blockSize must be a power of two.
</span><span class="cx">
</span><span class="cx"> static const size_t atomsPerBlock = blockSize / atomSize;
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreheapWeakBlockh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/heap/WeakBlock.h (182877 => 182878)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/heap/WeakBlock.h 2015-04-16 02:53:44 UTC (rev 182877)
+++ trunk/Source/JavaScriptCore/heap/WeakBlock.h 2015-04-16 03:40:14 UTC (rev 182878)
</span><span class="lines">@@ -41,7 +41,7 @@
</span><span class="cx"> class WeakBlock : public DoublyLinkedListNode<WeakBlock> {
</span><span class="cx"> public:
</span><span class="cx"> friend class WTF::DoublyLinkedListNode<WeakBlock>;
</span><del>- static const size_t blockSize = 4 * KB; // 5% of MarkedBlock size
</del><ins>+ static const size_t blockSize = 1 * KB; // 1/16 of MarkedBlock size
</ins><span class="cx">
</span><span class="cx"> struct FreeCell {
</span><span class="cx"> FreeCell* next;
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorellintLLIntDatacpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/llint/LLIntData.cpp (182877 => 182878)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/llint/LLIntData.cpp 2015-04-16 02:53:44 UTC (rev 182877)
+++ trunk/Source/JavaScriptCore/llint/LLIntData.cpp 2015-04-16 03:40:14 UTC (rev 182878)
</span><span class="lines">@@ -153,7 +153,7 @@
</span><span class="cx">
</span><span class="cx"> ASSERT(ResolveModeAndType::mask == 0xffff);
</span><span class="cx">
</span><del>- ASSERT(MarkedBlock::blockMask == ~static_cast<decltype(MarkedBlock::blockMask)>(0xffff));
</del><ins>+ ASSERT(MarkedBlock::blockMask == ~static_cast<decltype(MarkedBlock::blockMask)>(0x3fff));
</ins><span class="cx">
</span><span class="cx"> // FIXME: make these assertions less horrible.
</span><span class="cx"> #if !ASSERT_DISABLED
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorellintLowLevelInterpreterasm"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/llint/LowLevelInterpreter.asm (182877 => 182878)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/llint/LowLevelInterpreter.asm 2015-04-16 02:53:44 UTC (rev 182877)
+++ trunk/Source/JavaScriptCore/llint/LowLevelInterpreter.asm 2015-04-16 03:40:14 UTC (rev 182878)
</span><span class="lines">@@ -196,7 +196,7 @@
</span><span class="cx">
</span><span class="cx"> const ResolveModeMask = 0xffff
</span><span class="cx">
</span><del>-const MarkedBlockSize = 64 * 1024
</del><ins>+const MarkedBlockSize = 16 * 1024
</ins><span class="cx"> const MarkedBlockMask = ~(MarkedBlockSize - 1)
</span><span class="cx"> # Constants for checking mark bits.
</span><span class="cx"> const AtomNumberShift = 3
</span></span></pre>
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