Support higher CPU profiler sampling rate on posix systems

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 @@
 #include "../include/v8-profiler.h"
 
 namespace v8 {
 namespace internal {
 
 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),
       last_code_event_id_(0), last_processed_code_event_id_(0) {
 }
 
 
 void ProfilerEventsProcessor::Enqueue(const CodeEventsContainer& event) {
   event.generic.order = ++last_code_event_id_;
   events_buffer_.Enqueue(event);
@@ skipping 67 matching lines @@
     // 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();
   }
 }
 
 
+void ProfilerEventsProcessor::ProcessEventsAndDoSample() {
+  int64_t stop_time = OS::Ticks() + period_in_useconds_;
+  // Keep processing existing events until we need to do next sample.
+  while (OS::Ticks() < stop_time) {
+    if (ProcessTicks()) {
+      // All ticks of the current dequeue_order are processed,
+      // proceed to the next code event.
+      ProcessCodeEvent();
+    }
+  }
+  // Schedule next sample. sampler_ is NULL in tests.
+  if (sampler_) sampler_->DoSample();
+}
+
+
+void ProfilerEventsProcessor::ProcessEventsAndYield() {
+  // Process ticks until we have any.
+  if (ProcessTicks()) {
+    // All ticks of the current dequeue_order are processed,
+    // proceed to the next code event.
+    ProcessCodeEvent();
+  }
+  YieldCPU();
+}
+
+
 void ProfilerEventsProcessor::Run() {
   while (running_) {
-    // Process ticks until we have any.
-    if (ProcessTicks()) {
-      // All ticks of the current last_processed_code_event_id_ are processed,
-      // proceed to the next code event.
-      ProcessCodeEvent();
+    if (Sampler::CanSampleOnProfilerEventsProcessorThread()) {
+      ProcessEventsAndDoSample();
+    } else {
+      ProcessEventsAndYield();
     }
-    YieldCPU();
   }
 
   // Process remaining tick events.
   ticks_buffer_.FlushResidualRecords();
   do {
     ProcessTicks();
   } while (ProcessCodeEvent());
 }
 
 
@@ skipping 263 matching lines @@
 }
 
 
 void CpuProfiler::StartProcessorIfNotStarted() {
   if (processor_ == NULL) {
     Logger* logger = isolate_->logger();
     // Disable logging when using the new implementation.
     saved_logging_nesting_ = logger->logging_nesting_;
     logger->logging_nesting_ = 0;
     generator_ = new ProfileGenerator(profiles_);
-    processor_ = new ProfilerEventsProcessor(generator_);
+    Sampler* sampler = logger->sampler();
+    processor_ = new ProfilerEventsProcessor(
+        generator_, sampler, FLAG_cpu_profiler_sampling_interval);
     is_profiling_ = true;
     processor_->StartSynchronously();
     // Enumerate stuff we already have in the heap.
     ASSERT(isolate_->heap()->HasBeenSetUp());
     if (!FLAG_prof_browser_mode) {
       logger->LogCodeObjects();
     }
     logger->LogCompiledFunctions();
     logger->LogAccessorCallbacks();
     LogBuiltins();
     // Enable stack sampling.
-    Sampler* sampler = logger->sampler();
+    if (Sampler::CanSampleOnProfilerEventsProcessorThread()) {
+      sampler->SetHasProcessingThread(true);
+    }
     sampler->IncreaseProfilingDepth();
     if (!sampler->IsActive()) {
       sampler->Start();
       need_to_stop_sampler_ = true;
     }
   }
 }
 
 
 CpuProfile* CpuProfiler::StopProfiling(const char* title) {
@@ skipping 17 matching lines @@
 
 void CpuProfiler::StopProcessorIfLastProfile(const char* title) {
   if (profiles_->IsLastProfile(title)) StopProcessor();
 }
 
 
 void CpuProfiler::StopProcessor() {
   Logger* logger = isolate_->logger();
   Sampler* sampler = reinterpret_cast<Sampler*>(logger->ticker_);
   sampler->DecreaseProfilingDepth();
-  if (need_to_stop_sampler_) {
-    sampler->Stop();
-    need_to_stop_sampler_ = false;
-  }
   is_profiling_ = false;
   processor_->StopSynchronously();
   delete processor_;
   delete generator_;
   processor_ = NULL;
   generator_ = NULL;
+  if (Sampler::CanSampleOnProfilerEventsProcessorThread()) {
+    sampler->SetHasProcessingThread(false);
+  }
+  if (need_to_stop_sampler_) {
+    sampler->Stop();
+    need_to_stop_sampler_ = false;
+  }
   logger->logging_nesting_ = saved_logging_nesting_;
 }
 
 
 void CpuProfiler::LogBuiltins() {
   Builtins* builtins = isolate_->builtins();
   ASSERT(builtins->is_initialized());
   for (int i = 0; i < Builtins::builtin_count; i++) {
     CodeEventsContainer evt_rec(CodeEventRecord::REPORT_BUILTIN);
     ReportBuiltinEventRecord* rec = &evt_rec.ReportBuiltinEventRecord_;
     Builtins::Name id = static_cast<Builtins::Name>(i);
     rec->start = builtins->builtin(id)->address();
     rec->builtin_id = id;
     processor_->Enqueue(evt_rec);
   }
 }
 
 
 } }  // namespace v8::internal