Moving cpu profiling into its own thread.

BUG=None

Review URL: https://codereview.chromium.org/10857035
Patch from Sergey Rogulenko <rogulenko@google.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12649 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/cpu-profiler.cc

@@ -45,10 +45,14 @@ 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),
@@ -206,8 +210,9 @@ bool ProfilerEventsProcessor::ProcessCodeEvent(unsigned* dequeue_order) {
 }
 
 
-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;
@@ -236,6 +241,19 @@ bool ProfilerEventsProcessor::ProcessTicks(unsigned dequeue_order) {
       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);
+    }
+  }
 }
 
 
@@ -243,19 +261,18 @@ 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)) {
+  }
 }
 
 
@@ -486,13 +503,15 @@ 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) {
@@ -505,12 +524,12 @@ void CpuProfiler::StartProcessorIfNotStarted() {
       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();
   }
 }
 
@@ -545,16 +564,16 @@ void CpuProfiler::StopProcessorIfLastProfile(const char* title) {
 
 
 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;

src/cpu-profiler.h

@@ -124,7 +124,9 @@ class TickSampleEventRecord {
 // methods called by event producers: VM and stack sampler threads.
 class ProfilerEventsProcessor : public Thread {
  public:
-  explicit ProfilerEventsProcessor(ProfileGenerator* generator);
+  explicit ProfilerEventsProcessor(ProfileGenerator* generator,
+                                   Sampler* sampler,
+                                   int period_in_useconds);
   virtual ~ProfilerEventsProcessor() {}
 
   // Thread control.
@@ -172,12 +174,16 @@ class ProfilerEventsProcessor : public Thread {
 
   // Called from events processing thread (Run() method.)
   bool ProcessCodeEvent(unsigned* dequeue_order);
-  bool ProcessTicks(unsigned dequeue_order);
+  bool ProcessTicks(int64_t stop_time, unsigned dequeue_order);
+  void ProcessEventsQueue(int64_t stop_time, unsigned* dequeue_order);
 
   INLINE(static bool FilterOutCodeCreateEvent(Logger::LogEventsAndTags tag));
 
   ProfileGenerator* generator_;
+  Sampler* sampler_;
   bool running_;
+  // Sampling period in microseconds.
+  const int period_in_useconds_;
   UnboundQueue<CodeEventsContainer> events_buffer_;
   SamplingCircularQueue ticks_buffer_;
   UnboundQueue<TickSampleEventRecord> ticks_from_vm_buffer_;

src/flag-definitions.h

@@ -335,6 +335,10 @@ DEFINE_bool(compilation_cache, true, "enable compilation cache")
 
 DEFINE_bool(cache_prototype_transitions, true, "cache prototype transitions")
 
+// cpu-profiler.cc
+DEFINE_int(cpu_profiler_sampling_period, 1000,
+           "CPU profiler sampling period in microseconds")
+
 // debug.cc
 DEFINE_bool(trace_debug_json, false, "trace debugging JSON request/response")
 DEFINE_bool(debugger_auto_break, true,

src/platform-cygwin.cc

@@ -768,6 +768,11 @@ Sampler::~Sampler() {
 }
 
 
+void Sampler::DoSample() {
+  // TODO(rogulenko): implement
+}
+
+
 void Sampler::Start() {
   ASSERT(!IsActive());
   SetActive(true);

src/platform-freebsd.cc

@@ -884,6 +884,11 @@ Sampler::~Sampler() {
 }
 
 
+void Sampler::DoSample() {
+  // TODO(rogulenko): implement
+}
+
+
 void Sampler::Start() {
   ASSERT(!IsActive());
   SetActive(true);

src/platform-linux.cc

@@ -1055,13 +1055,70 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
 }
 
 
-class Sampler::PlatformData : public Malloced {
+class CpuProfilerSignalHandler {
  public:
-  PlatformData() : vm_tid_(GetThreadID()) {}
+  static void SetUp() { if (!mutex_) mutex_ = OS::CreateMutex(); }
+  static void TearDown() { delete mutex_; }
 
-  int vm_tid() const { return vm_tid_; }
+  static void InstallSignalHandler() {
+    struct sigaction sa;
+    ScopedLock lock(mutex_);
+    if (signal_handler_installed_counter_ > 0) {
+      signal_handler_installed_counter_++;
+      return;
+    }
+    sa.sa_sigaction = ProfilerSignalHandler;
+    sigemptyset(&sa.sa_mask);
+    sa.sa_flags = SA_RESTART | SA_SIGINFO;
+    if (sigaction(SIGPROF, &sa, &old_signal_handler_) == 0) {
+      signal_handler_installed_counter_++;
+    }
+  }
+
+  static void RestoreSignalHandler() {
+    ScopedLock lock(mutex_);
+    if (signal_handler_installed_counter_ == 0)
+      return;
+    if (signal_handler_installed_counter_ == 1) {
+      sigaction(SIGPROF, &old_signal_handler_, 0);
+    }
+    signal_handler_installed_counter_--;
+  }
+
+  static bool signal_handler_installed() {
+    return signal_handler_installed_counter_ > 0;
+  }
 
  private:
+  static int signal_handler_installed_counter_;
+  static struct sigaction old_signal_handler_;
+  static Mutex* mutex_;
+};
+
+
+int CpuProfilerSignalHandler::signal_handler_installed_counter_ = 0;
+struct sigaction CpuProfilerSignalHandler::old_signal_handler_;
+Mutex* CpuProfilerSignalHandler::mutex_ = NULL;
+
+
+class Sampler::PlatformData : public Malloced {
+ public:
+  PlatformData()
+      : vm_tgid_(getpid()),
+        vm_tid_(GetThreadID()) {}
+
+  void SendProfilingSignal() {
+    if (!CpuProfilerSignalHandler::signal_handler_installed()) return;
+    // Glibc doesn't provide a wrapper for tgkill(2).
+#if defined(ANDROID)
+    syscall(__NR_tgkill, vm_tgid_, vm_tid_, SIGPROF);
+#else
+    syscall(SYS_tgkill, vm_tgid_, vm_tid_, SIGPROF);
+#endif
+  }
+
+ private:
+  const int vm_tgid_;
   const int vm_tid_;
 };
 
@@ -1077,28 +1134,11 @@ class SignalSender : public Thread {
 
   explicit SignalSender(int interval)
       : Thread(Thread::Options("SignalSender", kSignalSenderStackSize)),
-        vm_tgid_(getpid()),
         interval_(interval) {}
 
   static void SetUp() { if (!mutex_) mutex_ = OS::CreateMutex(); }
   static void TearDown() { delete mutex_; }
 
-  static void InstallSignalHandler() {
-    struct sigaction sa;
-    sa.sa_sigaction = ProfilerSignalHandler;
-    sigemptyset(&sa.sa_mask);
-    sa.sa_flags = SA_RESTART | SA_SIGINFO;
-    signal_handler_installed_ =
-        (sigaction(SIGPROF, &sa, &old_signal_handler_) == 0);
-  }
-
-  static void RestoreSignalHandler() {
-    if (signal_handler_installed_) {
-      sigaction(SIGPROF, &old_signal_handler_, 0);
-      signal_handler_installed_ = false;
-    }
-  }
-
   static void AddActiveSampler(Sampler* sampler) {
     ScopedLock lock(mutex_);
     SamplerRegistry::AddActiveSampler(sampler);
@@ -1119,7 +1159,6 @@ class SignalSender : public Thread {
       RuntimeProfiler::StopRuntimeProfilerThreadBeforeShutdown(instance_);
       delete instance_;
       instance_ = NULL;
-      RestoreSignalHandler();
     }
   }
 
@@ -1128,67 +1167,21 @@ class SignalSender : public Thread {
     SamplerRegistry::State state;
     while ((state = SamplerRegistry::GetState()) !=
            SamplerRegistry::HAS_NO_SAMPLERS) {
-      bool cpu_profiling_enabled =
-          (state == SamplerRegistry::HAS_CPU_PROFILING_SAMPLERS);
-      bool runtime_profiler_enabled = RuntimeProfiler::IsEnabled();
-      if (cpu_profiling_enabled && !signal_handler_installed_) {
-        InstallSignalHandler();
-      } else if (!cpu_profiling_enabled && signal_handler_installed_) {
-        RestoreSignalHandler();
-      }
-      // When CPU profiling is enabled both JavaScript and C++ code is
-      // profiled. We must not suspend.
-      if (!cpu_profiling_enabled) {
-        if (rate_limiter_.SuspendIfNecessary()) continue;
-      }
-      if (cpu_profiling_enabled && runtime_profiler_enabled) {
-        if (!SamplerRegistry::IterateActiveSamplers(&DoCpuProfile, this)) {
-          return;
-        }
-        Sleep(HALF_INTERVAL);
+      if (rate_limiter_.SuspendIfNecessary()) continue;
+      if (RuntimeProfiler::IsEnabled()) {
         if (!SamplerRegistry::IterateActiveSamplers(&DoRuntimeProfile, NULL)) {
           return;
         }
-        Sleep(HALF_INTERVAL);
-      } else {
-        if (cpu_profiling_enabled) {
-          if (!SamplerRegistry::IterateActiveSamplers(&DoCpuProfile,
-                                                      this)) {
-            return;
-          }
-        }
-        if (runtime_profiler_enabled) {
-          if (!SamplerRegistry::IterateActiveSamplers(&DoRuntimeProfile,
-                                                      NULL)) {
-            return;
-          }
-        }
-        Sleep(FULL_INTERVAL);
       }
+      Sleep(FULL_INTERVAL);
     }
   }
 
-  static void DoCpuProfile(Sampler* sampler, void* raw_sender) {
-    if (!sampler->IsProfiling()) return;
-    SignalSender* sender = reinterpret_cast<SignalSender*>(raw_sender);
-    sender->SendProfilingSignal(sampler->platform_data()->vm_tid());
-  }
-
   static void DoRuntimeProfile(Sampler* sampler, void* ignored) {
     if (!sampler->isolate()->IsInitialized()) return;
     sampler->isolate()->runtime_profiler()->NotifyTick();
   }
 
-  void SendProfilingSignal(int tid) {
-    if (!signal_handler_installed_) return;
-    // Glibc doesn't provide a wrapper for tgkill(2).
-#if defined(ANDROID)
-    syscall(__NR_tgkill, vm_tgid_, tid, SIGPROF);
-#else
-    syscall(SYS_tgkill, vm_tgid_, tid, SIGPROF);
-#endif
-  }
-
   void Sleep(SleepInterval full_or_half) {
     // Convert ms to us and subtract 100 us to compensate delays
     // occuring during signal delivery.
@@ -1211,15 +1204,12 @@ class SignalSender : public Thread {
 #endif  // ANDROID
   }
 
-  const int vm_tgid_;
   const int interval_;
   RuntimeProfilerRateLimiter rate_limiter_;
 
   // Protects the process wide state below.
   static Mutex* mutex_;
   static SignalSender* instance_;
-  static bool signal_handler_installed_;
-  static struct sigaction old_signal_handler_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SignalSender);
@@ -1228,8 +1218,6 @@ class SignalSender : public Thread {
 
 Mutex* SignalSender::mutex_ = NULL;
 SignalSender* SignalSender::instance_ = NULL;
-struct sigaction SignalSender::old_signal_handler_;
-bool SignalSender::signal_handler_installed_ = false;
 
 
 void OS::SetUp() {
@@ -1257,11 +1245,13 @@ void OS::SetUp() {
   }
 #endif
   SignalSender::SetUp();
+  CpuProfilerSignalHandler::SetUp();
 }
 
 
 void OS::TearDown() {
   SignalSender::TearDown();
+  CpuProfilerSignalHandler::TearDown();
   delete limit_mutex;
 }
 
@@ -1282,8 +1272,14 @@ Sampler::~Sampler() {
 }
 
 
+void Sampler::DoSample() {
+  platform_data()->SendProfilingSignal();
+}
+
+
 void Sampler::Start() {
   ASSERT(!IsActive());
+  CpuProfilerSignalHandler::InstallSignalHandler();
   SetActive(true);
   SignalSender::AddActiveSampler(this);
 }
@@ -1291,6 +1287,7 @@ void Sampler::Start() {
 
 void Sampler::Stop() {
   ASSERT(IsActive());
+  CpuProfilerSignalHandler::RestoreSignalHandler();
   SignalSender::RemoveActiveSampler(this);
   SetActive(false);
 }

src/platform-macos.cc

@@ -910,6 +910,11 @@ Sampler::~Sampler() {
 }
 
 
+void Sampler::DoSample() {
+  // TODO(rogulenko): implement
+}
+
+
 void Sampler::Start() {
   ASSERT(!IsActive());
   SetActive(true);

src/platform-openbsd.cc

@@ -964,6 +964,11 @@ Sampler::~Sampler() {
 }
 
 
+void Sampler::DoSample() {
+  // TODO(rogulenko): implement
+}
+
+
 void Sampler::Start() {
   ASSERT(!IsActive());
   SetActive(true);

src/platform-solaris.cc

@@ -887,6 +887,11 @@ Sampler::~Sampler() {
 }
 
 
+void Sampler::DoSample() {
+  // TODO(rogulenko): implement
+}
+
+
 void Sampler::Start() {
   ASSERT(!IsActive());
   SetActive(true);

src/platform-win32.cc

@@ -2114,6 +2114,11 @@ Sampler::~Sampler() {
 }
 
 
+void Sampler::DoSample() {
+  // TODO(rogulenko): implement
+}
+
+
 void Sampler::Start() {
   ASSERT(!IsActive());
   SetActive(true);

src/platform.h

@@ -741,6 +741,9 @@ class Sampler {
     IncSamplesTaken();
   }
 
+  // Performs platform-specific stack sampling.
+  void DoSample();
+
   // This method is called for each sampling period with the current
   // program counter.
   virtual void Tick(TickSample* sample) = 0;

test/cctest/test-cpu-profiler.cc

@@ -20,7 +20,7 @@ using i::TokenEnumerator;
 TEST(StartStop) {
   CpuProfilesCollection profiles;
   ProfileGenerator generator(&profiles);
-  ProfilerEventsProcessor processor(&generator);
+  ProfilerEventsProcessor processor(&generator, NULL, 1000);
   processor.Start();
   processor.Stop();
   processor.Join();
@@ -81,7 +81,7 @@ TEST(CodeEvents) {
   CpuProfilesCollection profiles;
   profiles.StartProfiling("", 1);
   ProfileGenerator generator(&profiles);
-  ProfilerEventsProcessor processor(&generator);
+  ProfilerEventsProcessor processor(&generator, NULL, 1000);
   processor.Start();
 
   // Enqueue code creation events.
@@ -142,7 +142,7 @@ TEST(TickEvents) {
   CpuProfilesCollection profiles;
   profiles.StartProfiling("", 1);
   ProfileGenerator generator(&profiles);
-  ProfilerEventsProcessor processor(&generator);
+  ProfilerEventsProcessor processor(&generator, NULL, 1000);
   processor.Start();
 
   processor.CodeCreateEvent(i::Logger::BUILTIN_TAG,
@@ -232,7 +232,7 @@ TEST(Issue1398) {
   CpuProfilesCollection profiles;
   profiles.StartProfiling("", 1);
   ProfileGenerator generator(&profiles);
-  ProfilerEventsProcessor processor(&generator);
+  ProfilerEventsProcessor processor(&generator, NULL, 1000);
   processor.Start();
 
   processor.CodeCreateEvent(i::Logger::BUILTIN_TAG,