Changeset 43619 in webkit for trunk/JavaScriptCore/bytecode/SamplingTool.h

Timestamp:

May 13, 2009, 2:10:02 AM (16 years ago)

Author:

[email protected]

Message:

2009-05-12 Gavin Barraclough <​[email protected]>

Reviewed by Oliver Hunt.

Add SamplingCounter tool to provide a simple mechanism for counting events in JSC
(enabled using ENABLE(SAMPLING_COUNTERS)). To count events within a single function
use the class 'SamplingCounter', where the counter may be incremented from multiple
functions 'GlobalSamplingCounter' may be convenient; all other counters (stack or
heap allocated, rather than statically declared) should use the DeletableSamplingCounter.
Further description of these classes is provided alongside their definition in
SamplingTool.h.

Counters may be incremented from c++ by calling the 'count()' method on the counter,
or may be incremented by JIT code by using the 'emitCount()' method within the JIT.

This patch also fixes CODEBLOCK_SAMPLING, which was missing a null pointer check.

• JavaScriptCore.exp:
• assembler/MacroAssemblerX86.h: (JSC::MacroAssemblerX86::addWithCarry32): (JSC::MacroAssemblerX86::and32): (JSC::MacroAssemblerX86::or32):
• assembler/MacroAssemblerX86Common.h: (JSC::MacroAssemblerX86Common::and32): (JSC::MacroAssemblerX86Common::or32):
• assembler/MacroAssemblerX86_64.h: (JSC::MacroAssemblerX86_64::and32): (JSC::MacroAssemblerX86_64::or32): (JSC::MacroAssemblerX86_64::addPtr):
• assembler/X86Assembler.h: (JSC::X86Assembler::): (JSC::X86Assembler::adcl_im): (JSC::X86Assembler::addq_im): (JSC::X86Assembler::andl_im): (JSC::X86Assembler::orl_im):
• bytecode/SamplingTool.cpp: (JSC::AbstractSamplingCounter::dump):
• bytecode/SamplingTool.h: (JSC::AbstractSamplingCounter::count): (JSC::GlobalSamplingCounter::name): (JSC::SamplingCounter::SamplingCounter):
• jit/JIT.h:
• jit/JITCall.cpp: (JSC::):
• jit/JITInlineMethods.h: (JSC::JIT::setSamplingFlag): (JSC::JIT::clearSamplingFlag): (JSC::JIT::emitCount):
• jsc.cpp: (runWithScripts):
• parser/Nodes.cpp: (JSC::ScopeNode::ScopeNode):
• wtf/Platform.h:

File:

• trunk/JavaScriptCore/bytecode/SamplingTool.h (modified) (1 diff)

trunk/JavaScriptCore/bytecode/SamplingTool.h

@@ -273 +273 @@
     };
 
+    // AbstractSamplingCounter:
+    //
+    // Implements a named set of counters, printed on exit if ENABLE(SAMPLING_COUNTERS).
+    // See subclasses below, SamplingCounter, GlobalSamplingCounter and DeletableSamplingCounter.
+    class AbstractSamplingCounter {
+        friend class JIT;
+        friend class DeletableSamplingCounter;
+    public:
+        void count(uint32_t count = 1)
+        {
+            m_counter += count;
+        }
+
+        static void dump();
+
+    protected:
+        // Effectively the contructor, however called lazily in the case of GlobalSamplingCounter.
+        void init(const char* name)
+        {
+            m_counter = 0;
+            m_name = name;
+
+            // Set m_next to point to the head of the chain, and inform whatever is
+            // currently at the head that this node will now hold the pointer to it.
+            m_next = s_abstractSamplingCounterChain;
+            s_abstractSamplingCounterChain->m_referer = &m_next;
+            // Add this node to the head of the list.
+            s_abstractSamplingCounterChain = this;
+            m_referer = &s_abstractSamplingCounterChain;
+        }
+
+        int64_t m_counter;
+        const char* m_name;
+        AbstractSamplingCounter* m_next;
+        // This is a pointer to the pointer to this node in the chain; used to
+        // allow fast linked list deletion.
+        AbstractSamplingCounter** m_referer;
+        // Null object used to detect end of static chain.
+        static AbstractSamplingCounter s_abstractSamplingCounterChainEnd;
+        static AbstractSamplingCounter* s_abstractSamplingCounterChain;
+        static bool s_completed;
+    };
+
+#if ENABLE(SAMPLING_COUNTERS)
+    // SamplingCounter:
+    //
+    // This class is suitable and (hopefully!) convenient for cases where a counter is
+    // required within the scope of a single function.  It can be instantiated as a
+    // static variable since it contains a constructor but not a destructor (static
+    // variables in WebKit cannot have destructors).
+    //
+    // For example:
+    //
+    // void someFunction()
+    // {
+    //     static SamplingCounter countMe("This is my counter.  There are many like it, but this one is mine.");
+    //     countMe.count();
+    //     // ...
+    // }
+    //
+    class SamplingCounter : public AbstractSamplingCounter {
+    public:
+        SamplingCounter(const char* name) { init(name); }
+    };
+
+    // GlobalSamplingCounter:
+    //
+    // This class is suitable for use where a counter is to be declared globally,
+    // since it contains neither a constructor nor destructor.  Instead, ensure
+    // that 'name()' is called to provide the counter with a name (and also to
+    // allow it to be printed out on exit).
+    //
+    // GlobalSamplingCounter globalCounter;
+    //
+    // void firstFunction()
+    // {
+    //     // Put this within a function that is definitely called!
+    //     // (Or alternatively alongside all calls to 'count()').
+    //     globalCounter.name("I Name You Destroyer.");
+    //     globalCounter.count();
+    //     // ...
+    // }
+    //
+    // void secondFunction()
+    // {
+    //     globalCounter.count();
+    //     // ...
+    // }
+    //
+    class GlobalSamplingCounter : public AbstractSamplingCounter {
+    public:
+        void name(const char* name)
+        {
+            // Global objects should be mapped in zero filled memory, so this should
+            // be a safe (albeit not necessarily threadsafe) check for 'first call'.
+            if (!m_next)
+                init(name);
+        }
+    };
+
+    // DeletableSamplingCounter:
+    //
+    // The above classes (SamplingCounter, GlobalSamplingCounter), are intended for
+    // use within a global or static scope, and as such cannot have a destructor.
+    // This means there is no convenient way for them to remove themselves from the
+    // static list of counters, and should an instance of either class be freed
+    // before 'dump()' has walked over the list it will potentially walk over an
+    // invalid pointer.
+    //
+    // This class is intended for use where the counter may possibly be deleted before
+    // the program exits.  Should this occur, the counter will print it's value to
+    // stderr, and remove itself from the static list.  Example:
+    //
+    // DeletableSamplingCounter* counter = new DeletableSamplingCounter("The Counter With No Name");
+    // counter->count();
+    // delete counter;
+    //
+    class DeletableSamplingCounter : public AbstractSamplingCounter {
+    public:
+        DeletableSamplingCounter(const char* name) { init(name); }
+
+        ~DeletableSamplingCounter()
+        {
+            if (!s_completed)
+                fprintf(stderr, "DeletableSamplingCounter \"%s\" deleted early (with count %lld)\n", m_name, m_counter);
+            // Our m_referer pointer should know where the pointer to this node is,
+            // and m_next should know that this node is the previous node in the list.
+            ASSERT(*m_referer == this);
+            ASSERT(m_next->m_referer == &m_next);
+            // Remove this node from the list, and inform m_next that we have done so.
+            m_next->m_referer = m_referer;
+            *m_referer = m_next;
+        }
+    };
+#endif
+
 } // namespace JSC