Add harness-cstats to collect C method stats

README.md

@@ -139,6 +139,7 @@ You can find several test harnesses in this repository:
 * harness-perf - a simplified harness that runs for exactly the hinted number of iterations
 * harness-bips - a harness that measures iterations/second until stable
 * harness-continuous - a harness that adjusts the batch sizes of iterations to run in stable iteration size batches
+* harness-cstats - count C method calls and C loop iterations
 
 To use it, run a benchmark script directly, specifying a harness directory with `-I`:
 

harness-cstats/harness.rb

@@ -0,0 +1,60 @@
+require_relative '../harness/harness'
+
+# Using Module#prepend to enable TracePoint right before #run_benchmark
+# while also reusing the original implementation.
+self.singleton_class.prepend Module.new {
+  def run_benchmark(*)
+    frames = []
+    c_calls = Hash.new { 0 }
+    c_loops = Hash.new { 0 }
+
+    method_trace = TracePoint.new(:call, :c_call, :return, :c_return) do |tp|
+      # Keep track of call frames to get the caller of :b_call
+      case tp.event
+      when :call, :c_call
+        method_name = "#{tp.defined_class}##{tp.method_id}"
+        frames.push([tp.event, method_name])
+      when :return, :c_return
+        frames.pop
+      end
+
+      # Count C method calls
+      if tp.event == :c_call
+        c_calls[method_name] += 1
+      end
+    end
+
+    block_trace = TracePoint.new(:b_call) do |tp|
+      caller_event, caller_method = frames.last
+
+      # Count block calls only when the caller is a C method
+      if caller_event == :c_call
+        c_loops[caller_method] += 1
+      end
+    end
+
+    method_trace.enable
+    block_trace.enable
+    super
+  ensure
+    block_trace.disable
+    method_trace.disable
+
+    c_loops_total = c_loops.sum(&:last)
+    c_loops = c_loops.sort_by { |_method, count| -count }.first(100)
+    c_loops_ratio = 100.0 * c_loops.sum(&:last) / c_loops_total
+    puts "Top #{c_loops.size} block calls by C methods (#{'%.1f' % c_loops_ratio}% of all #{c_loops_total} calls):"
+    c_loops.each do |method, count|
+      puts '%8d (%4.1f%%) %s' % [count, 100.0 * count / c_loops_total, method]
+    end
+    puts
+
+    c_calls_total = c_calls.sum(&:last)
+    c_calls = c_calls.sort_by { |_method, count| -count }.first(100)
+    c_calls_ratio = 100.0 * c_calls.sum(&:last) / c_calls_total
+    puts "Top #{c_calls.size} C method calls (#{'%.1f' % c_calls_ratio}% of all #{c_calls_total} calls):"
+    c_calls.sort_by(&:last).reverse.first(100).each do |method, count|
+      puts '%8d (%4.1f%%) %s' % [count, 100.0 * count / c_calls_total, method]
+    end
+  end
+}