Less aggressive polling when concurrently compiling for OSR.

src/optimizing-compiler-thread.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 35 matching lines @@
 class OptimizingCompilerThread : public Thread {
  public:
   explicit OptimizingCompilerThread(Isolate *isolate) :
       Thread("OptimizingCompilerThread"),
 #ifdef DEBUG
       thread_id_(0),
 #endif
       isolate_(isolate),
       stop_semaphore_(0),
       input_queue_semaphore_(0),
-      osr_candidates_(2),
-      ready_for_osr_(2),
+      osr_cursor_(0),
       osr_hits_(0),
       osr_attempts_(0) {
     NoBarrier_Store(&stop_thread_, static_cast<AtomicWord>(CONTINUE));
     NoBarrier_Store(&queue_length_, static_cast<AtomicWord>(0));
+    if (FLAG_concurrent_osr) {
+      osr_buffer_size_ = FLAG_concurrent_recompilation_queue_length + 4;
+      osr_buffer_ = NewArray<OptimizingCompiler*>(osr_buffer_size_);
+      for (int i = 0; i < osr_buffer_size_; i++) osr_buffer_[i] = NULL;
+    }
   }
-  ~OptimizingCompilerThread() {}
+
+  ~OptimizingCompilerThread() {
+    if (FLAG_concurrent_osr) DeleteArray(osr_buffer_);
+  }
 
   void Run();
   void Stop();
   void Flush();
   void QueueForOptimization(OptimizingCompiler* optimizing_compiler);
   void InstallOptimizedFunctions();
   OptimizingCompiler* FindReadyOSRCandidate(Handle<JSFunction> function,
                                             uint32_t osr_pc_offset);
   bool IsQueuedForOSR(Handle<JSFunction> function, uint32_t osr_pc_offset);
 
@@ skipping 13 matching lines @@
     return (current_length < FLAG_concurrent_recompilation_queue_length);
   }
 
 #ifdef DEBUG
   bool IsOptimizerThread();
 #endif
 
  private:
   enum StopFlag { CONTINUE, STOP, FLUSH };
 
-  // Remove the oldest OSR candidates that are ready so that we
-  // only have |limit| left waiting.
-  void RemoveStaleOSRCandidates(int limit = kReadyForOSRLimit);
-
   void FlushInputQueue(bool restore_function_code);
   void FlushOutputQueue(bool restore_function_code);
+  void FlushOsrBuffer(bool restore_function_code);
   void CompileNext();
 
+  // Add a recompilation task for OSR to the cyclic buffer, awaiting OSR entry.
+  // Tasks evicted from the cyclic buffer are discarded.
+  void AddToOsrBuffer(OptimizingCompiler* compiler);
+  void AdvanceOsrCursor() {
+    osr_cursor_ = (osr_cursor_ + 1) % osr_buffer_size_;
+  }
+
 #ifdef DEBUG
   int thread_id_;
   Mutex thread_id_mutex_;
 #endif
 
   Isolate* isolate_;
   Semaphore stop_semaphore_;
   Semaphore input_queue_semaphore_;
 
   // Queue of incoming recompilation tasks (including OSR).
   UnboundQueue<OptimizingCompiler*> input_queue_;
   // Queue of recompilation tasks ready to be installed (excluding OSR).
   UnboundQueue<OptimizingCompiler*> output_queue_;
-  // List of recompilation tasks for OSR in the input queue.
-  List<OptimizingCompiler*> osr_candidates_;
-  // List of recompilation tasks ready for OSR.
-  List<OptimizingCompiler*> ready_for_osr_;
+  // Cyclic buffer of recompilation tasks for OSR.
+  // TODO(yangguo): This may keep zombie tasks indefinitely, holding on to
+  //                a lot of memory.  Fix this.
+  OptimizingCompiler** osr_buffer_;
+  // Cursor for the cyclic buffer.
+  int osr_cursor_;
+  int osr_buffer_size_;
 
   volatile AtomicWord stop_thread_;
   volatile Atomic32 queue_length_;
   TimeDelta time_spent_compiling_;
   TimeDelta time_spent_total_;
 
   // TODO(yangguo): remove this once the memory leak has been figured out.
   Mutex queue_mutex_;
-  Mutex osr_list_mutex_;
   int osr_hits_;
   int osr_attempts_;
-
-  static const int kReadyForOSRLimit = 4;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OPTIMIZING_COMPILER_THREAD_H_