Collect only optimizable function samples....

src/runtime-profiler.cc

 // Copyright 2010 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 50 matching lines @@
  private:
   void Destroy();
   static void WeakCallback(v8::Persistent<v8::Value> object, void* data);
 
   PendingListNode* next_;
   Handle<Object> function_;  // Weak handle.
   int64_t start_;
 };
 
 
+enum SamplerState {
+  IN_NON_JS_STATE = 0,
+  IN_JS_STATE = 1
+};
+
+
 // Optimization sampler constants.
 static const int kSamplerFrameCount = 2;
 static const int kSamplerFrameWeight[kSamplerFrameCount] = { 2, 1 };
 static const int kSamplerWindowSize = 16;
 
-static const int kSamplerTicksDelta = 32;
+static const int kSamplerTicksBetweenThresholdAdjustment = 32;
 
 static const int kSamplerThresholdInit = 3;
 static const int kSamplerThresholdMin = 1;
 static const int kSamplerThresholdDelta = 1;
 
 static const int kSamplerThresholdSizeFactorInit = 3;
 static const int kSamplerThresholdSizeFactorMin = 1;
 static const int kSamplerThresholdSizeFactorDelta = 1;
 
 static const int kSizeLimit = 1500;
 
 static int sampler_threshold = kSamplerThresholdInit;
 static int sampler_threshold_size_factor = kSamplerThresholdSizeFactorInit;
 
+static int sampler_ticks_until_threshold_adjustment =
+    kSamplerTicksBetweenThresholdAdjustment;
+
+// The ratio of ticks spent in JS code in percent.
+static int js_ratio;
 
 // The JSFunctions in the sampler window are not GC safe. Old-space
 // pointers are not cleared during mark-sweep collection and therefore
 // the window might contain stale pointers. The window is updated on
 // scavenges and (parts of it) cleared on mark-sweep and
 // mark-sweep-compact.
 static Object* sampler_window[kSamplerWindowSize] = { NULL, };
 static int sampler_window_position = 0;
 static int sampler_window_weight[kSamplerWindowSize] = { 0, };
 
@@ skipping 159 matching lines @@
   // Run through the JavaScript frames and collect them. If we already
   // have a sample of the function, we mark it for optimizations
   // (eagerly or lazily).
   JSFunction* samples[kSamplerFrameCount];
   int count = 0;
   for (JavaScriptFrameIterator it;
        count < kSamplerFrameCount && !it.done();
        it.Advance()) {
     JavaScriptFrame* frame = it.frame();
     JSFunction* function = JSFunction::cast(frame->function());
-    int function_size = function->shared()->SourceSize();
-    int threshold_size_factor;
-    if (function_size > kSizeLimit) {
-      threshold_size_factor = sampler_threshold_size_factor;
-    } else {
-      threshold_size_factor = 1;
+
+    // Adjust threshold each time we have processed
+    // a certain number of ticks.
+    if (sampler_ticks_until_threshold_adjustment > 0) {
+      sampler_ticks_until_threshold_adjustment--;
+      if (sampler_ticks_until_threshold_adjustment == 0) {
+        // If the threshold is not already at the minimum
+        // modify and reset the ticks until next adjustment.
+        if (sampler_threshold > kSamplerThresholdMin) {
+          sampler_threshold -= kSamplerThresholdDelta;
+          sampler_ticks_until_threshold_adjustment =
+              kSamplerTicksBetweenThresholdAdjustment;
+        }
+      }
     }
 
+    // Do not record non-optimizable functions. If the function
+    // is not marked for recompilation, move on to the next frame.
+    if (!IsOptimizable(function)) {
+      if (!function->IsMarkedForLazyRecompilation()) continue;
+    } else {
+      samples[count++] = function;
+    }
+
+    int function_size = function->shared()->SourceSize();
+    int threshold_size_factor = (function_size > kSizeLimit)
+        ? sampler_threshold_size_factor
+        : 1;
+
     int threshold = sampler_threshold * threshold_size_factor;
-    samples[count++] = function;
+
+    // Adjust threshold depending on the ratio of time spent
+    // in JS code.
+    if (js_ratio < 20) {
+      // If we spent less than 20% of the time in JS, code

[Kasper Lund, 2010/12/09 11:51:51]

spent => spend

[Karl Klose, 2010/12/09 12:49:32]

Done.

+      // do not optimize.
+      if (!function->IsMarkedForLazyRecompilation()) continue;
+    } else if (js_ratio < 75) {
+      // Below 75% of time spent in JS code, only optimize very
+      // frequently used functions.
+      threshold *= 3;
+    }
+
     if (function->IsMarkedForLazyRecompilation()) {

[Kasper Lund, 2010/12/09 11:51:51]

Can't you just move this code up to the !IsOptimizable check and avoid the
repeated IsMarkedForLazyRecompilation checks?

[Karl Klose, 2010/12/09 12:49:32]

Done.

       Code* unoptimized = function->shared()->code();
       int nesting = unoptimized->allow_osr_at_loop_nesting_level();
       if (nesting == 0) AttemptOnStackReplacement(function);
       int new_nesting = Min(nesting + 1, Code::kMaxLoopNestingMarker);
       unoptimized->set_allow_osr_at_loop_nesting_level(new_nesting);
     } else if (LookupSample(function) >= threshold) {
-      if (IsOptimizable(function)) {
-        Optimize(function, false, 0);
-        CompilationCache::MarkForEagerOptimizing(Handle<JSFunction>(function));
-      }
+      Optimize(function, false, 0);
+      CompilationCache::MarkForEagerOptimizing(Handle<JSFunction>(function));
     }
   }
 
   // Add the collected functions as samples. It's important not to do
   // this as part of collecting them because this will interfere with
   // the sample lookup in case of recursive functions.
   for (int i = 0; i < count; i++) {
     AddSample(samples[i], kSamplerFrameWeight[i]);
   }
 }
@@ skipping 33 matching lines @@
 void RuntimeProfiler::Setup() {
   ClearSampleBuffer();
   // If the ticker hasn't already started, make sure to do so to get
   // the ticks for the runtime profiler.
   if (IsEnabled()) Logger::EnsureTickerStarted();
 }
 
 
 void RuntimeProfiler::Reset() {
   sampler_threshold = kSamplerThresholdInit;
+  sampler_ticks_until_threshold_adjustment =
+      kSamplerTicksBetweenThresholdAdjustment;
   sampler_threshold_size_factor = kSamplerThresholdSizeFactorInit;
 }
 
 
 void RuntimeProfiler::TearDown() {
   // Nothing to do.
 }
 
 
 Object** RuntimeProfiler::SamplerWindowAddress() {
   return sampler_window;
 }
 
 
 int RuntimeProfiler::SamplerWindowSize() {
   return kSamplerWindowSize;
 }
 
 
+static void AddStateSample(SamplerState current_state) {
+  static const int kStateWindowSize = 128;
+  static SamplerState state_window[kStateWindowSize];
+  static int state_window_position = 0;
+  static int state_counts[2] = { kStateWindowSize, 0 };
+
+  SamplerState old_state = state_window[state_window_position];
+  state_counts[old_state]--;
+  state_window[state_window_position] = current_state;
+  state_counts[current_state]++;
+  ASSERT(IsPowerOf2(kStateWindowSize));
+  state_window_position = (state_window_position + 1) &
+      (kStateWindowSize - 1);
+  js_ratio = state_counts[IN_JS_STATE]*100 / kStateWindowSize;

[Kasper Lund, 2010/12/09 11:51:51]

Spaces around *. Consider changing the type of js_ratio to Atomic32 and use the
NoBarrier_Store(&js_ratio, ...) here and NoBarrier_Load(&js_ratio, ...) in
OptimizeNow to load it into a local variable.

[Karl Klose, 2010/12/09 12:49:32]

Done.

+}
+
+
 bool RuntimeProfilerRateLimiter::SuspendIfNecessary() {
   static const int kNonJSTicksThreshold = 100;
   // We suspend the runtime profiler thread when not running
   // JavaScript. If the CPU profiler is active we must not do this
   // because it samples both JavaScript and C++ code.
   if (RuntimeProfiler::IsEnabled() &&
       !CpuProfiler::is_profiling() &&
       !(FLAG_prof && FLAG_prof_auto)) {
     if (Top::IsInJSState()) {
+      AddStateSample(IN_JS_STATE);
       non_js_ticks_ = 0;
     } else {
+      AddStateSample(IN_NON_JS_STATE);
       if (non_js_ticks_ < kNonJSTicksThreshold) {
         ++non_js_ticks_;
       } else {
         if (Top::WaitForJSState()) return true;
       }
     }
   }
   return false;
 }
 
 
 } }  // namespace v8::internal