Replacing circular queue by single buffer in CPU Profiler.

src/platform-cygwin.cc

 // 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 674 matching lines @@
   }
 
   void SampleContext(Sampler* sampler) {
     HANDLE profiled_thread = sampler->platform_data()->profiled_thread();
     if (profiled_thread == NULL) return;
 
     // Context used for sampling the register state of the profiled thread.
     CONTEXT context;
     memset(&context, 0, sizeof(context));
 
-    TickSample sample_obj;
-    TickSample* sample = CpuProfiler::TickSampleEvent(sampler->isolate());
-    if (sample == NULL) sample = &sample_obj;
+    TickSample* sample = CpuProfiler::StartTickSampleEvent(sampler->isolate());
+    if (sample == NULL) return;
 
     static const DWORD kSuspendFailed = static_cast<DWORD>(-1);
     if (SuspendThread(profiled_thread) == kSuspendFailed) return;
     sample->state = sampler->isolate()->current_vm_state();
 
     context.ContextFlags = CONTEXT_FULL;
     if (GetThreadContext(profiled_thread, &context) != 0) {
 #if V8_HOST_ARCH_X64
       sample->pc = reinterpret_cast<Address>(context.Rip);
       sample->sp = reinterpret_cast<Address>(context.Rsp);
       sample->fp = reinterpret_cast<Address>(context.Rbp);
 #else
       sample->pc = reinterpret_cast<Address>(context.Eip);
       sample->sp = reinterpret_cast<Address>(context.Esp);
       sample->fp = reinterpret_cast<Address>(context.Ebp);
 #endif
       sampler->SampleStack(sample);
       sampler->Tick(sample);
     }
+    CpuProfiler::FinishTickSampleEvent(sampler->isolate());
     ResumeThread(profiled_thread);
   }
 
   const int interval_;
   RuntimeProfilerRateLimiter rate_limiter_;
 
   // Protects the process wide state below.
   static Mutex* mutex_;
   static SamplerThread* instance_;
 
@@ skipping 54 matching lines @@
 
 
 void Sampler::Stop() {
   ASSERT(IsActive());
   SamplerThread::RemoveActiveSampler(this);
   SetActive(false);
 }
 
 
 } }  // namespace v8::internal