Changeset 173538 in webkit

Timestamp:

Sep 11, 2014, 1:58:02 PM (12 years ago)

Author:

ggaren@apple.com

Message:

bmalloc should segregate medium-sized objects by line like it does for small-sized objects
​https://bugs.webkit.org/show_bug.cgi?id=136693

Reviewed by Gavin Barraclough.

4% reduction in heap size on the MallocBench *_memory_warning benchmarks.

No throughput change.

We keep an array of medium allocators, just like our array of small
allocators.

In future, we can simplify the allocation fast path by merging the small
and medium allocator arrays. For now, this is the simplest change that
gets the win.

• bmalloc/Allocator.cpp:

(bmalloc::Allocator::Allocator):
(bmalloc::Allocator::scavenge):
(bmalloc::Allocator::allocateMedium):

• bmalloc/Allocator.h:
• bmalloc/Sizes.h:

(bmalloc::Sizes::mediumSizeClassFor):

Location:

trunk/Source/bmalloc

Files:

• ChangeLog (modified) (1 diff)
• bmalloc/Allocator.cpp (modified) (4 diffs)
• bmalloc/Allocator.h (modified) (1 diff)
• bmalloc/Sizes.h (modified) (2 diffs)

trunk/Source/bmalloc/ChangeLog

@@ +1 @@
+2014-09-11  Geoffrey Garen  <ggaren@apple.com>
+
+        bmalloc should segregate medium-sized objects by line like it does for small-sized objects
+        https://bugs.webkit.org/show_bug.cgi?id=136693
+
+        Reviewed by Gavin Barraclough.
+
+        4% reduction in heap size on the MallocBench *_memory_warning benchmarks.
+
+        No throughput change.
+
+        We keep an array of medium allocators, just like our array of small
+        allocators.
+
+        In future, we can simplify the allocation fast path by merging the small
+        and medium allocator arrays. For now, this is the simplest change that
+        gets the win.
+
+        * bmalloc/Allocator.cpp:
+        (bmalloc::Allocator::Allocator):
+        (bmalloc::Allocator::scavenge):
+        (bmalloc::Allocator::allocateMedium):
+        * bmalloc/Allocator.h:
+        * bmalloc/Sizes.h:
+        (bmalloc::Sizes::mediumSizeClassFor):
+
 2014-09-11  Geoffrey Garen  <ggaren@apple.com>
 

trunk/Source/bmalloc/bmalloc/Allocator.cpp

@@ -39 +39 @@
     : m_deallocator(deallocator)
     , m_smallAllocators()
-    , m_mediumAllocator()
+    , m_mediumAllocators()
     , m_smallAllocatorLog()
     , m_mediumAllocatorLog()
@@ -54 +54 @@
     scavenge();
 }
-    
+
 void Allocator::scavenge()
 {
@@ -63 +63 @@
     processSmallAllocatorLog();
 
-    retire(m_mediumAllocator);
-    m_mediumAllocator.clear();
+    for (auto& allocator : m_mediumAllocators) {
+        retire(allocator);
+        allocator.clear();
+    }
     processMediumAllocatorLog();
 }
@@ -130 +132 @@
 void* Allocator::allocateMedium(size_t size)
 {
-    MediumAllocator& allocator = m_mediumAllocator;
+    MediumAllocator& allocator = m_mediumAllocators[mediumSizeClassFor(size)];
     size = roundUpToMultipleOf<alignment>(size);
 

trunk/Source/bmalloc/bmalloc/Allocator.h

@@ -66 +66 @@
 
     std::array<SmallAllocator, smallMax / alignment> m_smallAllocators;
-    MediumAllocator m_mediumAllocator;
+    std::array<MediumAllocator, mediumMax / alignment> m_mediumAllocators;
 
     FixedVector<std::pair<SmallLine*, unsigned char>, smallAllocatorLogCapacity> m_smallAllocatorLog;

trunk/Source/bmalloc/bmalloc/Sizes.h

@@ -72 +72 @@
     static_assert(1 << largeAlignmentShift == largeAlignment, "largeAlignmentShift be log2(largeAlignment).");
     static const size_t largeMax = largeChunkSize * 99 / 100; // Plenty of room for metadata.
-    static const size_t largeMin = 1024;
+    static const size_t largeMin = mediumMax;
 
     static const size_t segregatedFreeListSearchDepth = 16;
@@ -98 +98 @@
         return mask((size - 1ul) / alignment, smallSizeClassMask);
     }
+
+    inline size_t mediumSizeClassFor(size_t size)
+    {
+        static const size_t mediumSizeClassMask = (mediumMax / alignment) - 1;
+        return mask((size - 1ul) / alignment, mediumSizeClassMask);
+    }
 };