Changeset 262362 in webkit for trunk/Source/JavaScriptCore/assembler/AssemblerBuffer.h

Timestamp:

May 31, 2020, 7:56:06 AM (5 years ago)

Author:

[email protected]

Message:

Consider a Thread Specific Cache for AssemblerBuffers
​https://bugs.webkit.org/show_bug.cgi?id=212562

Reviewed by Filip Pizlo.

This patch creates a thread local cache of AssemblerData in the hopes that it will reduce
memory allocation churn. The cache is cleared when a thread is destroyed.
If an AssemblerData is destroyed in another thread, its storage is cached by the
destroying thread.

Made a few changes described below to facilite the swap as well as returning a
clear()'ed AssemblerData back to its original state.

Reviewed by Filip Pizlo.

• assembler/AssemblerBuffer.cpp:

(JSC::threadSpecificAssemblerData):
(JSC::clearAssembleDataThreadSpecificCache):

• assembler/AssemblerBuffer.h:

(JSC::AssemblerData::AssemblerData):
(JSC::AssemblerData::operator=):
The copy constructor and assignment operator now perform complete AssemblerBuffer swaps.

(JSC::AssemblerData::takeBufferIfLarger):
A new method that will conditionally copy the enclosed buffer of the argument to "this"
if the argument's buffer is larger than the current buffer of "this".

(JSC::AssemblerData::~AssemblerData):
(JSC::AssemblerData::clear):
The destructor now calls clear which has been changed to reset the buffer to one with
inline capacity.

(JSC::AssemblerBuffer::AssemblerBuffer):
Take the cached out of line buffer if there is one.

(JSC::AssemblerBuffer::~AssemblerBuffer):
Cache the enclosed out of line buffer if it is larger than the currently cached one.

(JSC::AssemblerBuffer::getThreadSpecificAssemblerData):

• dfg/DFGWorklist.cpp:
• jit/JITWorklist.cpp:
• wasm/WasmWorklist.cpp:

File:

• trunk/Source/JavaScriptCore/assembler/AssemblerBuffer.h (modified) (5 diffs)

trunk/Source/JavaScriptCore/assembler/AssemblerBuffer.h

@@ -38 +38 @@
 #endif
 #include <wtf/StdLibExtras.h>
+#include <wtf/ThreadSpecific.h>
 #include <wtf/UnalignedAccess.h>
 
 namespace JSC {
+    class AssemblerData;
+
+    typedef ThreadSpecific<AssemblerData, WTF::CanBeGCThread::True> ThreadSpecificAssemblerData;
+
+    JS_EXPORT_PRIVATE ThreadSpecificAssemblerData& threadSpecificAssemblerData();
+    void clearAssembleDataThreadSpecificCache();
 
     class LinkBuffer;
@@ -100 +107 @@
             m_capacity = other.m_capacity;
 
-            other.m_buffer = nullptr;
-            other.m_capacity = 0;
+            other.m_buffer = other.m_inlineBuffer;
+            other.m_capacity = InlineCapacity;
         }
 
@@ -117 +124 @@
             m_capacity = other.m_capacity;
 
-            other.m_buffer = nullptr;
-            other.m_capacity = 0;
+            other.m_buffer = other.m_inlineBuffer;
+            other.m_capacity = InlineCapacity;
             return *this;
         }
 
-        ~AssemblerData()
-        {
+        void takeBufferIfLarger(AssemblerData&& other)
+        {
+            if (other.isInlineBuffer())
+                return;
+
+            if (m_capacity >= other.m_capacity)
+                return;
+
             if (m_buffer && !isInlineBuffer())
                 AssemblerDataMalloc::free(m_buffer);
+
+            m_buffer = other.m_buffer;
+            m_capacity = other.m_capacity;
+
+            other.m_buffer = other.m_inlineBuffer;
+            other.m_capacity = InlineCapacity;
+        }
+
+        ~AssemblerData()
+        {
+            clear();
+        }
+
+        void clear()
+        {
+            if (m_buffer && !isInlineBuffer()) {
+                AssemblerDataMalloc::free(m_buffer);
+                m_capacity = InlineCapacity;
+                m_buffer = m_inlineBuffer;
+            }
         }
 
@@ -178 +211 @@
             , m_index(0)
         {
+            auto& threadSpecific = getThreadSpecificAssemblerData();
+            m_storage.takeBufferIfLarger(WTFMove(*threadSpecific));
+        }
+
+        ~AssemblerBuffer()
+        {
+            auto& threadSpecific = getThreadSpecificAssemblerData();
+            threadSpecific->takeBufferIfLarger(WTFMove(m_storage));
         }
 
@@ -294 +335 @@
 
     protected:
+        ThreadSpecificAssemblerData& getThreadSpecificAssemblerData()
+        {
+            auto& threadSpecific = threadSpecificAssemblerData();
+
+            if (!threadSpecific.isSet()) {
+                void* ptr = static_cast<AssemblerData*>(threadSpecific);
+                new (ptr) AssemblerData();
+            }
+
+            return threadSpecific;
+        }
+        
         template<typename IntegralType>
         void putIntegral(IntegralType value)