Changeset 56435 in webkit for trunk/JavaScriptCore/runtime

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.

Location:

trunk/JavaScriptCore/runtime

Files:

• Collector.cpp (modified) (2 diffs)
• Collector.h (modified) (1 diff)

trunk/JavaScriptCore/runtime/Collector.cpp

@@ -981 +981 @@
 }
 
-void Heap::unprotect(JSValue k)
+bool Heap::unprotect(JSValue k)
 {
     ASSERT(k);
@@ -987 +987 @@
 
     if (!k.isCell())
-        return;
-
-    m_protectedValues.remove(k.asCell());
+        return false;
+
+    return m_protectedValues.remove(k.asCell());
 }
 

trunk/JavaScriptCore/runtime/Collector.h

@@ -96 +96 @@
 
         void protect(JSValue);
-        void unprotect(JSValue);
+        // Returns true if the value is no longer protected by any protect pointers
+        // (though it may still be alive due to heap/stack references).
+        bool unprotect(JSValue);
 
         static Heap* heap(JSValue); // 0 for immediate values