Moving cpu profiling into its own thread.

src/cpu-profiler.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 27 matching lines @@
 
 namespace v8 {
 namespace internal {
 
 static const int kEventsBufferSize = 256 * KB;
 static const int kTickSamplesBufferChunkSize = 64 * KB;
 static const int kTickSamplesBufferChunksCount = 16;
 static const int kProfilerStackSize = 64 * KB;
 
 
-ProfilerEventsProcessor::ProfilerEventsProcessor(ProfileGenerator* generator)
+ProfilerEventsProcessor::ProfilerEventsProcessor(ProfileGenerator* generator,
+                                                 Sampler* sampler,
+                                                 int period_in_useconds)
     : Thread(Thread::Options("v8:ProfEvntProc", kProfilerStackSize)),
       generator_(generator),
+      sampler_(sampler),
       running_(true),
+      period_in_useconds_(period_in_useconds),
       ticks_buffer_(sizeof(TickSampleEventRecord),
                     kTickSamplesBufferChunkSize,
                     kTickSamplesBufferChunksCount),
       enqueue_order_(0) {
 }
 
 
 void ProfilerEventsProcessor::CallbackCreateEvent(Logger::LogEventsAndTags tag,
                                                   const char* prefix,
                                                   String* name,
@@ skipping 137 matching lines @@
 #undef PROFILER_TYPE_CASE
       default: return true;  // Skip record.
     }
     *dequeue_order = record.generic.order;
     return true;
   }
   return false;
 }
 
 
-bool ProfilerEventsProcessor::ProcessTicks(unsigned dequeue_order) {
-  while (true) {
+bool ProfilerEventsProcessor::ProcessTicks(int64_t stop_time,
+                                           unsigned dequeue_order) {
+  while (stop_time == -1 || OS::Ticks() < stop_time) {
     if (!ticks_from_vm_buffer_.IsEmpty()
         && ticks_from_vm_buffer_.Peek()->order == dequeue_order) {
       TickSampleEventRecord record;
       ticks_from_vm_buffer_.Dequeue(&record);
       generator_->RecordTickSample(record.sample);
     }
 
     const TickSampleEventRecord* rec =
         TickSampleEventRecord::cast(ticks_buffer_.StartDequeue());
     if (rec == NULL) return !ticks_from_vm_buffer_.IsEmpty();
     // Make a local copy of tick sample record to ensure that it won't
     // be modified as we are processing it. This is possible as the
     // sampler writes w/o any sync to the queue, so if the processor
     // will get far behind, a record may be modified right under its
     // feet.
     TickSampleEventRecord record = *rec;
     if (record.order == dequeue_order) {
       // A paranoid check to make sure that we don't get a memory overrun
       // in case of frames_count having a wild value.
       if (record.sample.frames_count < 0
           || record.sample.frames_count > TickSample::kMaxFramesCount)
         record.sample.frames_count = 0;
       generator_->RecordTickSample(record.sample);
       ticks_buffer_.FinishDequeue();
     } else {
       return true;
     }
   }
+  return false;
+}
+
+
+void ProfilerEventsProcessor::ProcessEventsQueue(int64_t stop_time,
+                                                 unsigned* dequeue_order) {
+  while (OS::Ticks() < stop_time) {
+    if (ProcessTicks(stop_time, *dequeue_order)) {
+      // All ticks of the current dequeue_order are processed,
+      // proceed to the next code event.
+      ProcessCodeEvent(dequeue_order);
+    }
+  }
 }
 
 
 void ProfilerEventsProcessor::Run() {
   unsigned dequeue_order = 0;
 
   while (running_) {
-    // Process ticks until we have any.
-    if (ProcessTicks(dequeue_order)) {
-      // All ticks of the current dequeue_order are processed,
-      // proceed to the next code event.
-      ProcessCodeEvent(&dequeue_order);
+    int64_t stop_time = OS::Ticks() + period_in_useconds_;
+    if (sampler_ != NULL) {
+      sampler_->DoSample();
     }
-    YieldCPU();
+    ProcessEventsQueue(stop_time, &dequeue_order);
   }
 
   // Process remaining tick events.
   ticks_buffer_.FlushResidualRecords();
   // Perform processing until we have tick events, skip remaining code events.
-  while (ProcessTicks(dequeue_order) && ProcessCodeEvent(&dequeue_order)) { }
+  while (ProcessTicks(-1, dequeue_order) && ProcessCodeEvent(&dequeue_order)) {
+  }
 }
 
 
 void CpuProfiler::StartProfiling(const char* title) {
   ASSERT(Isolate::Current()->cpu_profiler() != NULL);
   Isolate::Current()->cpu_profiler()->StartCollectingProfile(title);
 }
 
 
 void CpuProfiler::StartProfiling(String* title) {
@@ skipping 210 matching lines @@
 
 void CpuProfiler::StartCollectingProfile(String* title) {
   StartCollectingProfile(profiles_->GetName(title));
 }
 
 
 void CpuProfiler::StartProcessorIfNotStarted() {
   if (processor_ == NULL) {
     Isolate* isolate = Isolate::Current();
 
+    Sampler* sampler = isolate->logger()->sampler();
     // Disable logging when using the new implementation.
     saved_logging_nesting_ = isolate->logger()->logging_nesting_;
     isolate->logger()->logging_nesting_ = 0;
     generator_ = new ProfileGenerator(profiles_);
-    processor_ = new ProfilerEventsProcessor(generator_);
+    processor_ = new ProfilerEventsProcessor(generator_,
+                                             sampler,
+                                             FLAG_cpu_profiler_sampling_period);
     NoBarrier_Store(&is_profiling_, true);
-    processor_->Start();
     // Enumerate stuff we already have in the heap.
     if (isolate->heap()->HasBeenSetUp()) {
       if (!FLAG_prof_browser_mode) {
         bool saved_log_code_flag = FLAG_log_code;
         FLAG_log_code = true;
         isolate->logger()->LogCodeObjects();
         FLAG_log_code = saved_log_code_flag;
       }
       isolate->logger()->LogCompiledFunctions();
       isolate->logger()->LogAccessorCallbacks();
     }
     // Enable stack sampling.
-    Sampler* sampler = reinterpret_cast<Sampler*>(isolate->logger()->ticker_);
     if (!sampler->IsActive()) {
       sampler->Start();
       need_to_stop_sampler_ = true;
     }
     sampler->IncreaseProfilingDepth();
+    processor_->Start();
   }
 }
 
 
 CpuProfile* CpuProfiler::StopCollectingProfile(const char* title) {
   const double actual_sampling_rate = generator_->actual_sampling_rate();
   StopProcessorIfLastProfile(title);
   CpuProfile* result =
       profiles_->StopProfiling(TokenEnumerator::kNoSecurityToken,
                                title,
@@ skipping 14 matching lines @@
   return profiles_->StopProfiling(token, profile_title, actual_sampling_rate);
 }
 
 
 void CpuProfiler::StopProcessorIfLastProfile(const char* title) {
   if (profiles_->IsLastProfile(title)) StopProcessor();
 }
 
 
 void CpuProfiler::StopProcessor() {
+  NoBarrier_Store(&is_profiling_, false);
+  processor_->Stop();
+  processor_->Join();
   Logger* logger = Isolate::Current()->logger();
-  Sampler* sampler = reinterpret_cast<Sampler*>(logger->ticker_);
+  Sampler* sampler = logger->sampler();
   sampler->DecreaseProfilingDepth();
   if (need_to_stop_sampler_) {
     sampler->Stop();
     need_to_stop_sampler_ = false;
   }
-  NoBarrier_Store(&is_profiling_, false);
-  processor_->Stop();
-  processor_->Join();
   delete processor_;
   delete generator_;
   processor_ = NULL;
   generator_ = NULL;
   logger->logging_nesting_ = saved_logging_nesting_;
 }
 
 
 void CpuProfiler::SetUp() {
   Isolate* isolate = Isolate::Current();
   if (isolate->cpu_profiler() == NULL) {
     isolate->set_cpu_profiler(new CpuProfiler());
   }
 }
 
 
 void CpuProfiler::TearDown() {
   Isolate* isolate = Isolate::Current();
   if (isolate->cpu_profiler() != NULL) {
     delete isolate->cpu_profiler();
   }
   isolate->set_cpu_profiler(NULL);
 }
 
 } }  // namespace v8::internal