1 files changed, 68 insertions, 0 deletions
diff --git a/lib/mjit/stats.rb b/lib/mjit/stats.rb
new file mode 100644
index 0000000000..263948bc0e
--- /dev/null
+++ b/lib/mjit/stats.rb
@@ -0,0 +1,68 @@
+# frozen_string_literal: true
+module RubyVM::MJIT
+  def self.runtime_stats
+    stats = {}
+
+    # Insn exits
+    INSNS.each_value do |insn|
+      exits = C.mjit_insn_exits[insn.bin]
+      if exits > 0
+        stats[:"exit_#{insn.name}"] = exits
+      end
+    end
+
+    # Runtime stats
+    C.rb_mjit_runtime_counters.members.each do |member|
+      stats[member] = C.rb_mjit_counters.public_send(member)
+    end
+
+    # Other stats are calculated here
+    stats[:side_exit_count] = stats.select { |name, _count| name.start_with?('exit_') }.sum(&:last)
+    if stats[:vm_insns_count] > 0
+      retired_in_mjit = stats[:mjit_insns_count] - stats[:side_exit_count]
+      stats[:total_insns_count] = retired_in_mjit + stats[:vm_insns_count]
+      stats[:ratio_in_mjit] = 100.0 * retired_in_mjit / stats[:total_insns_count]
+    end
+
+    stats
+  end
+
+  at_exit do
+    if C.mjit_opts.stats
+      print_stats
+    end
+  end
+
+  class << self
+    private
+
+    def print_stats
+      stats = runtime_stats
+      $stderr.puts("***MJIT: Printing MJIT statistics on exit***")
+
+      $stderr.puts "side_exit_count:       #{format('%10d', stats[:side_exit_count])}"
+      $stderr.puts "total_insns_count:     #{format('%10d', stats[:total_insns_count])}" if stats.key?(:total_insns_count)
+      $stderr.puts "vm_insns_count:        #{format('%10d', stats[:vm_insns_count])}" if stats.key?(:vm_insns_count)
+      $stderr.puts "mjit_insns_count:      #{format('%10d', stats[:mjit_insns_count])}"
+      $stderr.puts "ratio_in_yjit:         #{format('%9.1f', stats[:ratio_in_mjit])}%" if stats.key?(:ratio_in_mjit)
+
+      print_exit_counts(stats)
+    end
+
+    def print_exit_counts(stats, how_many: 20, padding: 2)
+      exits = stats.filter_map { |name, count| [name.to_s.delete_prefix('exit_'), count] if name.start_with?('exit_') }.to_h
+      return if exits.empty?
+
+      top_exits = exits.sort_by { |_name, count| -count }.first(how_many).to_h
+      total_exits = exits.values.sum
+      $stderr.puts "Top-#{top_exits.size} most frequent exit ops (#{format("%.1f", 100.0 * top_exits.values.sum / total_exits)}% of exits):"
+
+      name_width  = top_exits.map { |name, _count| name.length }.max + padding
+      count_width = top_exits.map { |_name, count| count.to_s.length }.max + padding
+      top_exits.each do |name, count|
+        ratio = 100.0 * count / total_exits
+        $stderr.puts "#{format("%#{name_width}s", name)}: #{format("%#{count_width}d", count)} (#{format('%.1f', ratio)}%)"
+      end
+    end
+  end
+end