Changeset 56435 in webkit for trunk/JavaScriptCore/wtf/HashCountedSet.h

Timestamp:

Mar 24, 2010, 12:11:51 AM (15 years ago)

Author:

[email protected]

Message:

Bug 36519 - JSGlobalContextRelease is unnecessarily slow

Reviewed by Oliver Hunt.

Since [ ​http://trac.webkit.org/changeset/35917 ], calling
JSGlobalContextRelease always triggers a GC heap collection
(if not a full destroy). As per 35917's changelog "This is
only really necessary when the (JSGlobalObject's) last
reference is released, but there is no way to determine that,
and no harm in collecting slightly more often."

Well, we now know of cases of API clients who are harmed by
the performance penalty of collecting too often, so it's time
to add a way to determine whether a call to JSGlobalContextRelease
is removing the last protect from it's global object. If further
protects are retaining the global object (likely from other
JSGlobalContextRefs), then don't trigger a GC collection.

• API/JSContextRef.cpp:
• runtime/Collector.cpp:

(JSC::Heap::unprotect): return a boolean indicating that the value is now unprotected.

• runtime/Collector.h:
• wtf/HashCountedSet.h:

(WTF::::remove): return a boolean indicating whether the value was removed from the set.

File:

• trunk/JavaScriptCore/wtf/HashCountedSet.h (modified) (3 diffs)

trunk/JavaScriptCore/wtf/HashCountedSet.h

@@ -44 +44 @@
         bool isEmpty() const;
         
-        // iterators iterate over pairs of values and counts
+        // Iterators iterate over pairs of values and counts.
         iterator begin();
         iterator end();
@@ -55 +55 @@
         unsigned count(const ValueType&) const;
 
-        // increases the count if an equal value is already present
-        // the return value is a pair of an interator to the new value's location, 
-        // and a bool that is true if an new entry was added
+        // Increases the count if an equal value is already present
+        // the return value is a pair of an interator to the new value's 
+        // location, and a bool that is true if an new entry was added.
         std::pair<iterator, bool> add(const ValueType&);
         
-        // reduces the count of the value, and removes it if count
-        // goes down to zero
-        void remove(const ValueType&);
-        void remove(iterator);
+        // Reduces the count of the value, and removes it if count
+        // goes down to zero, returns true if the value is removed.
+        bool remove(const ValueType&);
+        bool remove(iterator);
  
-        // removes the value, regardless of its count
+        // Removes the value, regardless of its count.
         void removeAll(iterator);
         void removeAll(const ValueType&);
 
-        // clears the whole set
+        // Clears the whole set.
         void clear();
 
@@ -151 +151 @@
     
     template<typename Value, typename HashFunctions, typename Traits>
-    inline void HashCountedSet<Value, HashFunctions, Traits>::remove(const ValueType& value)
-    {
-        remove(find(value));
-    }
-    
-    template<typename Value, typename HashFunctions, typename Traits>
-    inline void HashCountedSet<Value, HashFunctions, Traits>::remove(iterator it)
+    inline bool HashCountedSet<Value, HashFunctions, Traits>::remove(const ValueType& value)
+    {
+        return remove(find(value));
+    }
+    
+    template<typename Value, typename HashFunctions, typename Traits>
+    inline bool HashCountedSet<Value, HashFunctions, Traits>::remove(iterator it)
     {
         if (it == end())
-            return;
+            return false;
 
         unsigned oldVal = it->second;
-        ASSERT(oldVal != 0);
+        ASSERT(oldVal);
         unsigned newVal = oldVal - 1;
-        if (newVal == 0)
-            m_impl.remove(it);
-        else
+        if (newVal) {
             it->second = newVal;
+            return false;
+        }
+
+        m_impl.remove(it);
+        return true;
     }