Moving cpu profiling into its own thread.

src/platform-linux.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 1062 matching lines @@
     FULL_INTERVAL
   };
 
   static const int kSignalSenderStackSize = 64 * KB;
 
   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 SetUp() {
+    if (!mutex_) mutex_ = OS::CreateMutex();
+    InstallSignalHandler();

[caseq, 2012/08/16 14:39:22]

So SignalSender has nothing to do with CPU profiling after your change, yet you
install/remove signal handler within SignalSender.

+  }
+  static void TearDown() {
+    RestoreSignalHandler();
+    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);
   }
 
@@ skipping 26 matching lines @@
       instance_ = NULL;
       RestoreSignalHandler();
     }
   }
 
   // Implement Thread::Run().
   virtual void Run() {
     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 (runtime_profiler_enabled) {
         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.
     useconds_t interval = interval_ * 1000 - 100;
     if (full_or_half == HALF_INTERVAL) interval /= 2;
 #if defined(ANDROID)
     usleep(interval);
 #else
     int result = usleep(interval);
 #ifdef DEBUG
@@ skipping 87 matching lines @@
 }
 
 
 void Sampler::Stop() {
   ASSERT(IsActive());
   SignalSender::RemoveActiveSampler(this);
   SetActive(false);
 }
 
 
+CpuProfilerThread::CpuProfilerThread(Sampler* sampler)
+    : Thread(Thread::Options("CpuProfiler", kCpuProfilerThreadStackSize)),
+      vm_tgid_(getpid()),
+      sampler_(sampler) {
+}
+
+
+void CpuProfilerThread::DoCpuProfile() {

[caseq, 2012/08/16 14:39:22]

DoCpuProfile -> DoSample?

+  int tid = sampler_->platform_data()->vm_tid();
+  if (!SignalSender::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
+}
+
+
 } }  // namespace v8::internal