Make CPU profiler do not hog 100% of CPU.

Tick event processor should not stay in a tight loop
when there's nothing to do. It can go sleep until next sample event.

LOG=N
BUG=v8:3967

Review URL: https://codereview.chromium.org/1118533003

Cr-Commit-Position: refs/heads/master@{#28211}

src/base/platform/platform-posix.cc

@@ -219,9 +219,8 @@ size_t OS::AllocateAlignment() {
 }
 
 
-void OS::Sleep(int milliseconds) {
-  useconds_t ms = static_cast<useconds_t>(milliseconds);
-  usleep(1000 * ms);
+void OS::Sleep(TimeDelta interval) {
+  usleep(static_cast<useconds_t>(interval.InMicroseconds()));
 }
 
 

src/base/platform/platform-win32.cc

@@ -812,8 +812,8 @@ void OS::Guard(void* address, const size_t size) {
 }
 
 
-void OS::Sleep(int milliseconds) {
-  ::Sleep(milliseconds);
+void OS::Sleep(TimeDelta interval) {
+  ::Sleep(static_cast<DWORD>(interval.InMilliseconds()));
 }
 
 

src/base/platform/platform.h

@@ -190,8 +190,8 @@ class OS {
   // Get the Alignment guaranteed by Allocate().
   static size_t AllocateAlignment();
 
-  // Sleep for a number of milliseconds.
-  static void Sleep(const int milliseconds);
+  // Sleep for a specified time interval.
+  static void Sleep(TimeDelta interval);
 
   // Abort the current process.
   static void Abort();

src/cpu-profiler.cc

@@ -120,16 +120,32 @@ ProfilerEventsProcessor::SampleProcessingResult
 
 void ProfilerEventsProcessor::Run() {
   while (!!base::NoBarrier_Load(&running_)) {
-    base::ElapsedTimer timer;
-    timer.Start();
-    // Keep processing existing events until we need to do next sample.
+    base::TimeTicks nextSampleTime =
+        base::TimeTicks::HighResolutionNow() + period_;
+    base::TimeTicks now;
+    SampleProcessingResult result;
+    // Keep processing existing events until we need to do next sample
+    // or the ticks buffer is empty.
     do {
-      if (FoundSampleForNextCodeEvent == ProcessOneSample()) {
+      result = ProcessOneSample();
+      if (result == FoundSampleForNextCodeEvent) {
         // All ticks of the current last_processed_code_event_id_ are
         // processed, proceed to the next code event.
         ProcessCodeEvent();
       }
-    } while (!timer.HasExpired(period_));
+      now = base::TimeTicks::HighResolutionNow();
+    } while (result != NoSamplesInQueue && now < nextSampleTime);
+
+    if (nextSampleTime > now) {
+#if V8_OS_WIN
+      // Do not use Sleep on Windows as it is very imprecise.
+      // Could be up to 16ms jitter, which is unacceptable for the purpose.
+      while (base::TimeTicks::HighResolutionNow() < nextSampleTime) {
+      }
+#else
+      base::OS::Sleep(nextSampleTime - now);
+#endif
+    }
 
     // Schedule next sample. sampler_ is NULL in tests.
     if (sampler_) sampler_->DoSample();

src/optimizing-compile-dispatcher.cc

@@ -63,7 +63,8 @@ class OptimizingCompileDispatcher::CompileTask : public v8::Task {
       TimerEventScope<TimerEventRecompileConcurrent> timer(isolate_);
 
       if (dispatcher->recompilation_delay_ != 0) {
-        base::OS::Sleep(dispatcher->recompilation_delay_);
+        base::OS::Sleep(base::TimeDelta::FromMilliseconds(
+            dispatcher->recompilation_delay_));
       }
 
       dispatcher->CompileNext(dispatcher->NextInput(true));

src/runtime/runtime-test.cc

@@ -176,7 +176,7 @@ RUNTIME_FUNCTION(Runtime_GetOptimizationStatus) {
       sync_with_compiler_thread) {
     while (function->IsInOptimizationQueue()) {
       isolate->optimizing_compile_dispatcher()->InstallOptimizedFunctions();
-      base::OS::Sleep(50);
+      base::OS::Sleep(base::TimeDelta::FromMilliseconds(50));
     }
   }
   if (FLAG_always_opt) {

src/sampler.cc

@@ -558,7 +558,7 @@ class SamplerThread : public base::Thread {
           sampler->DoSample();
         }
       }
-      base::OS::Sleep(interval_);
+      base::OS::Sleep(base::TimeDelta::FromMilliseconds(interval_));
     }
   }
 

test/cctest/test-api.cc

@@ -13095,10 +13095,12 @@ class RegExpInterruptionThread : public v8::base::Thread {
          v8::base::NoBarrier_Load(&regexp_interruption_data.loop_count) < 7;
          v8::base::NoBarrier_AtomicIncrement(
              &regexp_interruption_data.loop_count, 1)) {
-      v8::base::OS::Sleep(50);  // Wait a bit before requesting GC.
+      // Wait a bit before requesting GC.
+      v8::base::OS::Sleep(v8::base::TimeDelta::FromMilliseconds(50));
       reinterpret_cast<i::Isolate*>(isolate_)->stack_guard()->RequestGC();
     }
-    v8::base::OS::Sleep(50);  // Wait a bit before terminating.
+    // Wait a bit before terminating.
+    v8::base::OS::Sleep(v8::base::TimeDelta::FromMilliseconds(50));
     v8::V8::TerminateExecution(isolate_);
   }
 
@@ -18812,7 +18814,7 @@ class ThreadInterruptTest {
       struct sigaction action;
 
       // Ensure that we'll enter waiting condition
-      v8::base::OS::Sleep(100);
+      v8::base::OS::Sleep(v8::base::TimeDelta::FromMilliseconds(100));
 
       // Setup signal handler
       memset(&action, 0, sizeof(action));
@@ -18823,7 +18825,7 @@ class ThreadInterruptTest {
       kill(getpid(), SIGCHLD);
 
       // Ensure that if wait has returned because of error
-      v8::base::OS::Sleep(100);
+      v8::base::OS::Sleep(v8::base::TimeDelta::FromMilliseconds(100));
 
       // Set value and signal semaphore
       test_->sem_value_ = 1;

test/cctest/test-cpu-profiler.cc

@@ -807,7 +807,7 @@ class TestApiCallbacks {
     double start = v8::base::OS::TimeCurrentMillis();
     double duration = 0;
     while (duration < min_duration_ms_) {
-      v8::base::OS::Sleep(1);
+      v8::base::OS::Sleep(v8::base::TimeDelta::FromMilliseconds(1));
       duration = v8::base::OS::TimeCurrentMillis() - start;
     }
   }

test/cctest/test-log.cc

@@ -190,7 +190,7 @@ class LoopingJsThread : public LoopingThread {
             "var j; for (var i=0; i<10000; ++i) { j = Math.sin(i); }");
       }
       context.Dispose();
-      i::OS::Sleep(1);
+      i::OS::Sleep(v8::base::TimeDelta::FromMilliseconds(1));
     }
   }
 };
@@ -210,7 +210,7 @@ class LoopingNonJsThread : public LoopingThread {
     SignalRunning();
     while (IsRunning()) {
       i = std::sin(i);
-      i::OS::Sleep(1);
+      i::OS::Sleep(v8::base::TimeDelta::FromMilliseconds(1));
     }
   }
 };