Collect only optimizable function samples....

src/runtime-profiler.cc

Index: src/runtime-profiler.cc
===================================================================
--- src/runtime-profiler.cc	(revision 5952)
+++ src/runtime-profiler.cc	(working copy)
@@ -68,12 +68,18 @@
 };
 
 
+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;
@@ -88,7 +94,12 @@
 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 Atomic32 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
@@ -267,28 +278,58 @@
        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;
+        }
+      }
     }
 
-    int threshold = sampler_threshold * threshold_size_factor;
-    samples[count++] = function;
     if (function->IsMarkedForLazyRecompilation()) {
       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));
-      }
     }
+
+    // Do not record non-optimizable functions.
+    if (!IsOptimizable(function)) continue;
+    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;
+    int current_js_ratio = NoBarrier_Load(&js_ratio);
+
+    // Adjust threshold depending on the ratio of time spent
+    // in JS code.
+    if (current_js_ratio < 20) {
+      // If we spend less than 20% of the time in JS code,
+      // do not optimize.
+      continue;
+    } else if (current_js_ratio < 75) {
+      // Below 75% of time spent in JS code, only optimize very
+      // frequently used functions.
+      threshold *= 3;
+    }
+
+    if (LookupSample(function) >= threshold) {
+      Optimize(function, false, 0);
+      CompilationCache::MarkForEagerOptimizing(Handle<JSFunction>(function));
+    }
   }
 
   // Add the collected functions as samples. It's important not to do
@@ -341,6 +382,8 @@
 
 void RuntimeProfiler::Reset() {
   sampler_threshold = kSamplerThresholdInit;
+  sampler_ticks_until_threshold_adjustment =
+      kSamplerTicksBetweenThresholdAdjustment;
   sampler_threshold_size_factor = kSamplerThresholdSizeFactorInit;
 }
 
@@ -360,6 +403,24 @@
 }
 
 
+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);
+  NoBarrier_Store(&js_ratio, state_counts[IN_JS_STATE] * 100 /
+                  kStateWindowSize);
+}
+
+
 bool RuntimeProfilerRateLimiter::SuspendIfNecessary() {
   static const int kNonJSTicksThreshold = 100;
   // We suspend the runtime profiler thread when not running
@@ -369,8 +430,10 @@
       !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 {