Replacing circular queue by single buffer in CPU Profiler.

BUG=None

Review URL: https://codereview.chromium.org/10871039
Patch from Sergey Rogulenko <rogulenko@google.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12650 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/cpu-profiler-inl.h

@@ -31,7 +31,6 @@
 #include "cpu-profiler.h"
 
 #include <new>
-#include "circular-queue-inl.h"
 #include "profile-generator-inl.h"
 #include "unbound-queue-inl.h"
 
@@ -56,11 +55,18 @@ void SharedFunctionInfoMoveEventRecord::UpdateCodeMap(CodeMap* code_map) {
 }
 
 
-TickSample* ProfilerEventsProcessor::TickSampleEvent() {
+TickSample* ProfilerEventsProcessor::StartTickSampleEvent() {
+  if (!ticks_buffer_is_empty_ || ticks_buffer_is_initialized_) return NULL;
+  ticks_buffer_is_initialized_ = true;
   generator_->Tick();
-  TickSampleEventRecord* evt =
-      new(ticks_buffer_.Enqueue()) TickSampleEventRecord(enqueue_order_);
-  return &evt->sample;
+  ticks_buffer_ = TickSampleEventRecord(enqueue_order_);
+  return &ticks_buffer_.sample;
+}
+
+
+void ProfilerEventsProcessor::FinishTickSampleEvent() {
+  ASSERT(ticks_buffer_is_initialized_ && ticks_buffer_is_empty_);
+  ticks_buffer_is_empty_ = false;
 }
 
 

src/cpu-profiler.cc

@@ -39,9 +39,6 @@
 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;
 
 
@@ -53,9 +50,8 @@ ProfilerEventsProcessor::ProfilerEventsProcessor(ProfileGenerator* generator,
       sampler_(sampler),
       running_(true),
       period_in_useconds_(period_in_useconds),
-      ticks_buffer_(sizeof(TickSampleEventRecord),
-                    kTickSamplesBufferChunkSize,
-                    kTickSamplesBufferChunksCount),
+      ticks_buffer_is_empty_(true),
+      ticks_buffer_is_initialized_(false),
       enqueue_order_(0) {
 }
 
@@ -210,9 +206,8 @@ bool ProfilerEventsProcessor::ProcessCodeEvent(unsigned* dequeue_order) {
 }
 
 
-bool ProfilerEventsProcessor::ProcessTicks(int64_t stop_time,
-                                           unsigned dequeue_order) {
-  while (stop_time == -1 || OS::Ticks() < stop_time) {
+bool ProfilerEventsProcessor::ProcessTicks(unsigned dequeue_order) {
+  while (true) {
     if (!ticks_from_vm_buffer_.IsEmpty()
         && ticks_from_vm_buffer_.Peek()->order == dequeue_order) {
       TickSampleEventRecord record;
@@ -220,35 +215,28 @@ bool ProfilerEventsProcessor::ProcessTicks(int64_t stop_time,
       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) {
+    if (ticks_buffer_is_empty_) return !ticks_from_vm_buffer_.IsEmpty();
+    if (ticks_buffer_.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();
+      if (ticks_buffer_.sample.frames_count < 0
+          || ticks_buffer_.sample.frames_count > TickSample::kMaxFramesCount) {
+        ticks_buffer_.sample.frames_count = 0;
+      }
+      generator_->RecordTickSample(ticks_buffer_.sample);
+      ticks_buffer_is_empty_ = true;
+      ticks_buffer_is_initialized_ = false;
     } 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)) {
+    if (ProcessTicks(*dequeue_order)) {
       // All ticks of the current dequeue_order are processed,
       // proceed to the next code event.
       ProcessCodeEvent(dequeue_order);
@@ -268,11 +256,7 @@ void ProfilerEventsProcessor::Run() {
     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(-1, dequeue_order) && ProcessCodeEvent(&dequeue_order)) {
-  }
+  while (ProcessTicks(dequeue_order) && ProcessCodeEvent(&dequeue_order)) { }
 }
 
 
@@ -327,15 +311,22 @@ CpuProfile* CpuProfiler::FindProfile(Object* security_token, unsigned uid) {
 }
 
 
-TickSample* CpuProfiler::TickSampleEvent(Isolate* isolate) {
+TickSample* CpuProfiler::StartTickSampleEvent(Isolate* isolate) {
   if (CpuProfiler::is_profiling(isolate)) {
-    return isolate->cpu_profiler()->processor_->TickSampleEvent();
+    return isolate->cpu_profiler()->processor_->StartTickSampleEvent();
   } else {
     return NULL;
   }
 }
 
 
+void CpuProfiler::FinishTickSampleEvent(Isolate* isolate) {
+  if (CpuProfiler::is_profiling(isolate)) {
+    isolate->cpu_profiler()->processor_->FinishTickSampleEvent();
+  }
+}
+
+
 void CpuProfiler::DeleteAllProfiles() {
   Isolate* isolate = Isolate::Current();
   ASSERT(isolate->cpu_profiler() != NULL);

src/cpu-profiler.h

@@ -158,11 +158,12 @@ class ProfilerEventsProcessor : public Thread {
   // Puts current stack into tick sample events buffer.
   void AddCurrentStack();
 
-  // Tick sample events are filled directly in the buffer of the circular
-  // queue (because the structure is of fixed width, but usually not all
-  // stack frame entries are filled.) This method returns a pointer to the
-  // next record of the buffer.
-  INLINE(TickSample* TickSampleEvent());
+  // StartTickSampleEvent returns a pointer only if the ticks_buffer_ is empty,
+  // FinishTickSampleEvent marks the ticks_buffer_ as filled.
+  // Finish should be called only after successful Start (returning non-NULL
+  // pointer).
+  INLINE(TickSample* StartTickSampleEvent());
+  INLINE(void FinishTickSampleEvent());
 
  private:
   union CodeEventsContainer {
@@ -174,7 +175,7 @@ class ProfilerEventsProcessor : public Thread {
 
   // Called from events processing thread (Run() method.)
   bool ProcessCodeEvent(unsigned* dequeue_order);
-  bool ProcessTicks(int64_t stop_time, unsigned dequeue_order);
+  bool ProcessTicks(unsigned dequeue_order);
   void ProcessEventsQueue(int64_t stop_time, unsigned* dequeue_order);
 
   INLINE(static bool FilterOutCodeCreateEvent(Logger::LogEventsAndTags tag));
@@ -185,7 +186,9 @@ class ProfilerEventsProcessor : public Thread {
   // Sampling period in microseconds.
   const int period_in_useconds_;
   UnboundQueue<CodeEventsContainer> events_buffer_;
-  SamplingCircularQueue ticks_buffer_;
+  TickSampleEventRecord ticks_buffer_;
+  bool ticks_buffer_is_empty_;
+  bool ticks_buffer_is_initialized_;
   UnboundQueue<TickSampleEventRecord> ticks_from_vm_buffer_;
   unsigned enqueue_order_;
 };
@@ -224,7 +227,10 @@ class CpuProfiler {
   static bool HasDetachedProfiles();
 
   // Invoked from stack sampler (thread or signal handler.)
-  static TickSample* TickSampleEvent(Isolate* isolate);
+  // Finish should be called only after successful Start (returning non-NULL
+  // pointer).
+  static TickSample* StartTickSampleEvent(Isolate* isolate);
+  static void FinishTickSampleEvent(Isolate* isolate);
 
   // Must be called via PROFILE macro, otherwise will crash when
   // profiling is not enabled.

src/platform-cygwin.cc

@@ -692,9 +692,8 @@ class SamplerThread : public 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;
@@ -714,6 +713,7 @@ class SamplerThread : public Thread {
       sampler->SampleStack(sample);
       sampler->Tick(sample);
     }
+    CpuProfiler::FinishTickSampleEvent(sampler->isolate());
     ResumeThread(profiled_thread);
   }
 

src/platform-freebsd.cc

@@ -678,9 +678,8 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
   Sampler* sampler = isolate->logger()->sampler();
   if (sampler == NULL || !sampler->IsActive()) return;
 
-  TickSample sample_obj;
-  TickSample* sample = CpuProfiler::TickSampleEvent(isolate);
-  if (sample == NULL) sample = &sample_obj;
+  TickSample* sample = CpuProfiler::StartTickSampleEvent(isolate);
+  if (sample == NULL) return;
 
   // Extracting the sample from the context is extremely machine dependent.
   ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(context);
@@ -701,6 +700,7 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
 #endif
   sampler->SampleStack(sample);
   sampler->Tick(sample);
+  CpuProfiler::FinishTickSampleEvent(isolate);
 }
 
 

src/platform-linux.cc

@@ -1015,9 +1015,8 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
   Sampler* sampler = isolate->logger()->sampler();
   if (sampler == NULL || !sampler->IsActive()) return;
 
-  TickSample sample_obj;
-  TickSample* sample = CpuProfiler::TickSampleEvent(isolate);
-  if (sample == NULL) sample = &sample_obj;
+  TickSample* sample = CpuProfiler::StartTickSampleEvent(isolate);
+  if (sample == NULL) return;
 
   // Extracting the sample from the context is extremely machine dependent.
   ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(context);
@@ -1052,6 +1051,7 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
 #endif  // V8_HOST_ARCH_*
   sampler->SampleStack(sample);
   sampler->Tick(sample);
+  CpuProfiler::FinishTickSampleEvent(isolate);
 }
 
 

src/platform-macos.cc

@@ -819,9 +819,8 @@ class SamplerThread : public Thread {
 
   void SampleContext(Sampler* sampler) {
     thread_act_t profiled_thread = sampler->platform_data()->profiled_thread();
-    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;
 
     if (KERN_SUCCESS != thread_suspend(profiled_thread)) return;
 
@@ -858,6 +857,7 @@ class SamplerThread : public Thread {
       sampler->SampleStack(sample);
       sampler->Tick(sample);
     }
+    CpuProfiler::FinishTickSampleEvent(sampler->isolate());
     thread_resume(profiled_thread);
   }
 

src/platform-openbsd.cc

@@ -731,9 +731,8 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
   Sampler* sampler = isolate->logger()->sampler();
   if (sampler == NULL || !sampler->IsActive()) return;
 
-  TickSample sample_obj;
-  TickSample* sample = CpuProfiler::TickSampleEvent(isolate);
-  if (sample == NULL) sample = &sample_obj;
+  TickSample* sample = CpuProfiler::StartTickSampleEvent(isolate);
+  if (sample == NULL) return;
 
   // Extracting the sample from the context is extremely machine dependent.
   sample->state = isolate->current_vm_state();
@@ -762,6 +761,7 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
 #endif  // __NetBSD__
   sampler->SampleStack(sample);
   sampler->Tick(sample);
+  CpuProfiler::FinishTickSampleEvent(isolate);
 }
 
 

src/platform-solaris.cc

@@ -669,9 +669,8 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
   Sampler* sampler = isolate->logger()->sampler();
   if (sampler == NULL || !sampler->IsActive()) return;
 
-  TickSample sample_obj;
-  TickSample* sample = CpuProfiler::TickSampleEvent(isolate);
-  if (sample == NULL) sample = &sample_obj;
+  TickSample* sample = CpuProfiler::StartTickSampleEvent(isolate);
+  if (sample == NULL) return;
 
   // Extracting the sample from the context is extremely machine dependent.
   ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(context);
@@ -684,6 +683,7 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
 
   sampler->SampleStack(sample);
   sampler->Tick(sample);
+  CpuProfiler::FinishTickSampleEvent(isolate);
 }
 
 class Sampler::PlatformData : public Malloced {

src/platform-win32.cc

@@ -2038,9 +2038,8 @@ class SamplerThread : public 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;
@@ -2060,6 +2059,7 @@ class SamplerThread : public Thread {
       sampler->SampleStack(sample);
       sampler->Tick(sample);
     }
+    CpuProfiler::FinishTickSampleEvent(sampler->isolate());
     ResumeThread(profiled_thread);
   }
 

test/cctest/test-cpu-profiler.cc

@@ -5,6 +5,7 @@
 #include "v8.h"
 #include "cpu-profiler-inl.h"
 #include "cctest.h"
+#include "platform.h"
 #include "../include/v8-profiler.h"
 
 using i::CodeEntry;
@@ -38,11 +39,13 @@ static inline i::Address ToAddress(int n) {
   return reinterpret_cast<i::Address>(n);
 }
 
-static void EnqueueTickSampleEvent(ProfilerEventsProcessor* proc,
-                                   i::Address frame1,
-                                   i::Address frame2 = NULL,
-                                   i::Address frame3 = NULL) {
-  i::TickSample* sample = proc->TickSampleEvent();
+static void AddTickSampleEvent(ProfilerEventsProcessor* processor,
+                               i::Address frame1,
+                               i::Address frame2 = NULL,
+                               i::Address frame3 = NULL) {
+  i::TickSample* sample;
+  i::OS::Sleep(20);
+  while ((sample = processor->StartTickSampleEvent()) == NULL) i::OS::Sleep(20);
   sample->pc = frame1;
   sample->tos = frame1;
   sample->frames_count = 0;
@@ -54,6 +57,7 @@ static void EnqueueTickSampleEvent(ProfilerEventsProcessor* proc,
     sample->stack[1] = frame3;
     sample->frames_count = 2;
   }
+  processor->FinishTickSampleEvent();
 }
 
 namespace {
@@ -108,8 +112,8 @@ TEST(CodeEvents) {
   processor.CodeMoveEvent(ToAddress(0x1400), ToAddress(0x1500));
   processor.CodeCreateEvent(i::Logger::STUB_TAG, 3, ToAddress(0x1600), 0x10);
   processor.CodeCreateEvent(i::Logger::STUB_TAG, 4, ToAddress(0x1605), 0x10);
-  // Enqueue a tick event to enable code events processing.
-  EnqueueTickSampleEvent(&processor, ToAddress(0x1000));
+  // Add a tick event to enable code events processing.
+  AddTickSampleEvent(&processor, ToAddress(0x1000));
 
   processor.Stop();
   processor.Join();
@@ -154,12 +158,12 @@ TEST(TickEvents) {
                             "ddd",
                             ToAddress(0x1400),
                             0x80);
-  EnqueueTickSampleEvent(&processor, ToAddress(0x1210));
-  EnqueueTickSampleEvent(&processor, ToAddress(0x1305), ToAddress(0x1220));
-  EnqueueTickSampleEvent(&processor,
-                         ToAddress(0x1404),
-                         ToAddress(0x1305),
-                         ToAddress(0x1230));
+  AddTickSampleEvent(&processor, ToAddress(0x1210));
+  AddTickSampleEvent(&processor, ToAddress(0x1305), ToAddress(0x1220));
+  AddTickSampleEvent(&processor,
+                     ToAddress(0x1404),
+                     ToAddress(0x1305),
+                     ToAddress(0x1230));
 
   processor.Stop();
   processor.Join();
@@ -240,13 +244,14 @@ TEST(Issue1398) {
                             ToAddress(0x1200),
                             0x80);
 
-  i::TickSample* sample = processor.TickSampleEvent();
+  i::TickSample* sample = processor.StartTickSampleEvent();
   sample->pc = ToAddress(0x1200);
   sample->tos = 0;
   sample->frames_count = i::TickSample::kMaxFramesCount;
   for (int i = 0; i < sample->frames_count; ++i) {
     sample->stack[i] = ToAddress(0x1200);
   }
+  processor.FinishTickSampleEvent();
 
   processor.Stop();
   processor.Join();