yjit.rb

   1 # frozen_string_literal: true
   2
   3 # This module allows for introspection of YJIT, CRuby's experimental in-process
   4 # just-in-time compiler. This module exists only to help develop YJIT, as such,
   5 # everything in the module is highly implementation specific and comes with no
   6 # API stability guarantee whatsoever.
   7 #
   8 # This module may not exist if YJIT does not support the particular platform
   9 # for which CRuby is built. There is also no API stability guarantee as to in
  10 # what situations this module is defined.
  11 module RubyVM::YJIT
  12   if defined?(Disasm)
  13     def self.disasm(iseq, tty: $stdout && $stdout.tty?)
  14       iseq = RubyVM::InstructionSequence.of(iseq)
  15
  16       blocks = blocks_for(iseq)
  17       return if blocks.empty?
  18
  19       str = String.new
  20       str << iseq.disasm
  21       str << "\n"
  22
  23       # Sort the blocks by increasing addresses
  24       sorted_blocks = blocks.sort_by(&:address)
  25
  26       highlight = ->(str) {
  27         if tty
  28           "\x1b[1m#{str}\x1b[0m"
  29         else
  30           str
  31         end
  32       }
  33
  34       cs = Disasm.new
  35       sorted_blocks.each_with_index do |block, i|
  36         str << "== BLOCK #{i+1}/#{blocks.length}: #{block.code.length} BYTES, ISEQ RANGE [#{block.iseq_start_index},#{block.iseq_end_index}) ".ljust(80, "=")
  37         str << "\n"
  38
  39         comments = comments_for(block.address, block.address + block.code.length)
  40         comment_idx = 0
  41         cs.disasm(block.code, block.address).each do |i|
  42           while (comment = comments[comment_idx]) && comment.address <= i.address
  43             str << "  ; #{highlight.call(comment.comment)}\n"
  44             comment_idx += 1
  45           end
  46
  47           str << sprintf(
  48             "  %<address>08x:  %<instruction>s\t%<details>s\n",
  49             address: i.address,
  50             instruction: i.mnemonic,
  51             details: i.op_str
  52           )
  53         end
  54       end
  55
  56       block_sizes = blocks.map { |block| block.code.length }
  57       total_bytes = block_sizes.sum
  58       str << "\n"
  59       str << "Total code size: #{total_bytes} bytes"
  60       str << "\n"
  61
  62       str
  63     end
  64
  65     def self.comments_for(start_address, end_address)
  66       Primitive.comments_for(start_address, end_address)
  67     end
  68
  69     def self.graphviz_for(iseq)
  70       iseq = RubyVM::InstructionSequence.of(iseq)
  71       cs = Disasm.new
  72
  73       highlight = ->(comment) { "<b>#{comment}</b>" }
  74       linebreak = "<br align=\"left\"/>\n"
  75
  76       buff = +''
  77       blocks = blocks_for(iseq).sort_by(&:id)
  78       buff << "digraph g {\n"
  79
  80       # Write the iseq info as a legend
  81       buff << "  legend [shape=record fontsize=\"30\" fillcolor=\"lightgrey\" style=\"filled\"];\n"
  82       buff << "  legend [label=\"{ Instruction Disassembly For: | {#{iseq.base_label}@#{iseq.absolute_path}:#{iseq.first_lineno}}}\"];\n"
  83
  84       # Subgraph contains disassembly
  85       buff << "  subgraph disasm {\n"
  86       buff << "  node [shape=record fontname=\"courier\"];\n"
  87       buff << "  edge [fontname=\"courier\" penwidth=3];\n"
  88       blocks.each do |block|
  89         disasm = disasm_block(cs, block, highlight)
  90
  91         # convert newlines to breaks that graphviz understands
  92         disasm.gsub!(/\n/, linebreak)
  93
  94         # strip leading whitespace
  95         disasm.gsub!(/^\s+/, '')
  96
  97         buff << "b#{block.id} [label=<#{disasm}>];\n"
  98         buff << block.outgoing_ids.map { |id|
  99           next_block = blocks.bsearch { |nb| id <=> nb.id }
 100           if next_block.address == (block.address + block.code.length)
 101             "b#{block.id} -> b#{id}[label=\"Fall\"];"
 102           else
 103             "b#{block.id} -> b#{id}[label=\"Jump\" style=dashed];"
 104           end
 105         }.join("\n")
 106         buff << "\n"
 107       end
 108       buff << "  }"
 109       buff << "}"
 110       buff
 111     end
 112
 113     def self.disasm_block(cs, block, highlight)
 114       comments = comments_for(block.address, block.address + block.code.length)
 115       comment_idx = 0
 116       str = +''
 117       cs.disasm(block.code, block.address).each do |i|
 118         while (comment = comments[comment_idx]) && comment.address <= i.address
 119           str << "  ; #{highlight.call(comment.comment)}\n"
 120           comment_idx += 1
 121         end
 122
 123         str << sprintf(
 124           "  %<address>08x:  %<instruction>s\t%<details>s\n",
 125           address: i.address,
 126           instruction: i.mnemonic,
 127           details: i.op_str
 128         )
 129       end
 130       str
 131     end
 132   end
 133
 134   # Return a hash for statistics generated for the --yjit-stats command line option.
 135   # Return nil when option is not passed or unavailable.
 136   def self.runtime_stats
 137     # defined in yjit_iface.c
 138     Primitive.get_yjit_stats
 139   end
 140
 141   # Discard statistics collected for --yjit-stats.
 142   def self.reset_stats!
 143     # defined in yjit_iface.c
 144     Primitive.reset_stats_bang
 145   end
 146
 147   def self.stats_enabled?
 148     Primitive.yjit_stats_enabled_p
 149   end
 150
 151   def self.enabled?
 152     Primitive.cexpr! 'RBOOL(rb_yjit_enabled_p())'
 153   end
 154
 155   def self.simulate_oom!
 156     Primitive.simulate_oom_bang
 157   end
 158
 159   # Avoid calling a method here to not interfere with compilation tests
 160   if Primitive.yjit_stats_enabled_p
 161     at_exit { _print_stats }
 162   end
 163
 164   class << self
 165     private
 166
 167     # Format and print out counters
 168     def _print_stats
 169       stats = runtime_stats
 170       return unless stats
 171
 172       $stderr.puts("***YJIT: Printing YJIT statistics on exit***")
 173
 174       print_counters(stats, prefix: 'send_', prompt: 'method call exit reasons: ')
 175       print_counters(stats, prefix: 'invokesuper_', prompt: 'invokesuper exit reasons: ')
 176       print_counters(stats, prefix: 'leave_', prompt: 'leave exit reasons: ')
 177       print_counters(stats, prefix: 'gbpp_', prompt: 'getblockparamproxy exit reasons: ')
 178       print_counters(stats, prefix: 'getivar_', prompt: 'getinstancevariable exit reasons:')
 179       print_counters(stats, prefix: 'setivar_', prompt: 'setinstancevariable exit reasons:')
 180       print_counters(stats, prefix: 'oaref_', prompt: 'opt_aref exit reasons: ')
 181       print_counters(stats, prefix: 'expandarray_', prompt: 'expandarray exit reasons: ')
 182       print_counters(stats, prefix: 'opt_getinlinecache_', prompt: 'opt_getinlinecache exit reasons: ')
 183       print_counters(stats, prefix: 'invalidate_', prompt: 'invalidation reasons: ')
 184
 185       side_exits = total_exit_count(stats)
 186       total_exits = side_exits + stats[:leave_interp_return]
 187
 188       # Number of instructions that finish executing in YJIT.
 189       # See :count-placement: about the subtraction.
 190       retired_in_yjit = stats[:exec_instruction] - side_exits
 191
 192       # Average length of instruction sequences executed by YJIT
 193       avg_len_in_yjit = retired_in_yjit.to_f / total_exits
 194
 195       # Proportion of instructions that retire in YJIT
 196       total_insns_count = retired_in_yjit + stats[:vm_insns_count]
 197       yjit_ratio_pct = 100.0 * retired_in_yjit.to_f / total_insns_count
 198
 199       # Number of failed compiler invocations
 200       compilation_failure = stats[:compilation_failure]
 201
 202       $stderr.puts "bindings_allocations:  " + ("%10d" % stats[:binding_allocations])
 203       $stderr.puts "bindings_set:          " + ("%10d" % stats[:binding_set])
 204       $stderr.puts "compilation_failure:   " + ("%10d" % compilation_failure) if compilation_failure != 0
 205       $stderr.puts "compiled_iseq_count:   " + ("%10d" % stats[:compiled_iseq_count])
 206       $stderr.puts "compiled_block_count:  " + ("%10d" % stats[:compiled_block_count])
 207       $stderr.puts "invalidation_count:    " + ("%10d" % stats[:invalidation_count])
 208       $stderr.puts "constant_state_bumps:  " + ("%10d" % stats[:constant_state_bumps])
 209       $stderr.puts "inline_code_size:      " + ("%10d" % stats[:inline_code_size])
 210       $stderr.puts "outlined_code_size:    " + ("%10d" % stats[:outlined_code_size])
 211
 212       $stderr.puts "total_exit_count:      " + ("%10d" % total_exits)
 213       $stderr.puts "total_insns_count:     " + ("%10d" % total_insns_count)
 214       $stderr.puts "vm_insns_count:        " + ("%10d" % stats[:vm_insns_count])
 215       $stderr.puts "yjit_insns_count:      " + ("%10d" % stats[:exec_instruction])
 216       $stderr.puts "ratio_in_yjit:         " + ("%9.1f" % yjit_ratio_pct) + "%"
 217       $stderr.puts "avg_len_in_yjit:       " + ("%10.1f" % avg_len_in_yjit)
 218
 219       print_sorted_exit_counts(stats, prefix: "exit_")
 220     end
 221
 222     def print_sorted_exit_counts(stats, prefix:, how_many: 20, left_pad: 4)
 223       exits = []
 224       stats.each do |k, v|
 225         if k.start_with?(prefix)
 226           exits.push [k.to_s.delete_prefix(prefix), v]
 227         end
 228       end
 229
 230       exits = exits.sort_by { |name, count| -count }[0...how_many]
 231       total_exits = total_exit_count(stats)
 232
 233       top_n_total = exits.map { |name, count| count }.sum
 234       top_n_exit_pct = 100.0 * top_n_total / total_exits
 235
 236       $stderr.puts "Top-#{how_many} most frequent exit ops (#{"%.1f" % top_n_exit_pct}% of exits):"
 237
 238       longest_insn_name_len = exits.map { |name, count| name.length }.max
 239       exits.each do |name, count|
 240         padding = longest_insn_name_len + left_pad
 241         padded_name = "%#{padding}s" % name
 242         padded_count = "%10d" % count
 243         percent = 100.0 * count / total_exits
 244         formatted_percent = "%.1f" % percent
 245         $stderr.puts("#{padded_name}: #{padded_count} (#{formatted_percent}%)" )
 246       end
 247     end
 248
 249     def total_exit_count(stats, prefix: "exit_")
 250       total = 0
 251       stats.each do |k,v|
 252         total += v if k.start_with?(prefix)
 253       end
 254       total
 255     end
 256
 257     def print_counters(counters, prefix:, prompt:)
 258       $stderr.puts(prompt)
 259       counters = counters.filter { |key, _| key.start_with?(prefix) }
 260       counters.filter! { |_, value| value != 0 }
 261       counters.transform_keys! { |key| key.to_s.delete_prefix(prefix) }
 262
 263       if counters.empty?
 264         $stderr.puts("    (all relevant counters are zero)")
 265         return
 266       end
 267
 268       counters = counters.to_a
 269       counters.sort_by! { |(_, counter_value)| counter_value }
 270       longest_name_length = counters.max_by { |(name, _)| name.length }.first.length
 271       total = counters.sum { |(_, counter_value)| counter_value }
 272
 273       counters.reverse_each do |(name, value)|
 274         percentage = value.fdiv(total) * 100
 275         $stderr.printf("    %*s %10d (%4.1f%%)\n", longest_name_length, name, value, percentage);
 276       end
 277     end
 278   end
 279 end