Changeset 182878 in webkit

Timestamp:

Apr 15, 2015, 8:40:14 PM (11 years ago)

Author:

akling@apple.com

Message:

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:

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• heap/MarkedBlock.h (modified) (1 diff)
• heap/WeakBlock.h (modified) (1 diff)
• llint/LLIntData.cpp (modified) (1 diff)
• llint/LowLevelInterpreter.asm (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+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:
+
 2015-04-15  Jordan Harband  <ljharb@gmail.com>
 

trunk/Source/JavaScriptCore/heap/MarkedBlock.h

@@ -75 +75 @@
         static const size_t atomSize = 16; // bytes
         static const size_t atomShiftAmount = 4; // log_2(atomSize) FIXME: Change atomSize to 16.
-        static const size_t blockSize = 64 * KB;
+        static const size_t blockSize = 16 * KB;
         static const size_t blockMask = ~(blockSize - 1); // blockSize must be a power of two.
 

trunk/Source/JavaScriptCore/heap/WeakBlock.h

@@ -42 +42 @@
 public:
     friend class WTF::DoublyLinkedListNode<WeakBlock>;
-    static const size_t blockSize = 4 * KB; // 5% of MarkedBlock size
+    static const size_t blockSize = 1 * KB; // 1/16 of MarkedBlock size
 
     struct FreeCell {

trunk/Source/JavaScriptCore/llint/LLIntData.cpp

@@ -154 +154 @@
     ASSERT(ResolveModeAndType::mask == 0xffff);
 
-    ASSERT(MarkedBlock::blockMask == ~static_cast<decltype(MarkedBlock::blockMask)>(0xffff));
+    ASSERT(MarkedBlock::blockMask == ~static_cast<decltype(MarkedBlock::blockMask)>(0x3fff));
 
     // FIXME: make these assertions less horrible.

trunk/Source/JavaScriptCore/llint/LowLevelInterpreter.asm

@@ -197 +197 @@
 const ResolveModeMask = 0xffff
 
-const MarkedBlockSize = 64 * 1024
+const MarkedBlockSize = 16 * 1024
 const MarkedBlockMask = ~(MarkedBlockSize - 1)
 # Constants for checking mark bits.