RubyVM::YJIT

This module allows for introspection of YJIT, CRuby’s just-in-time compiler. Everything in the module is highly implementation specific and the API might be less stable compared to the standard library.

This module may not exist if YJIT does not support the particular platform for which CRuby is built.

Class Methods

code_gc

yjit.rb View on GitHub

          # File tmp/rubies/ruby-4.0.0/yjit.rb, line 253
def self.code_gc
  Primitive.rb_yjit_code_gc
end

Discard existing compiled code to reclaim memory and allow for recompilations in the future.

dump_exit_locations(filename)

yjit.rb View on GitHub

          # File tmp/rubies/ruby-4.0.0/yjit.rb, line 176
def self.dump_exit_locations(filename)
  unless trace_exit_locations_enabled?
    raise ArgumentError, "--yjit-trace-exits must be enabled to use dump_exit_locations."
  end

  File.binwrite(filename, Marshal.dump(RubyVM::YJIT.exit_locations))
end

Marshal dumps exit locations to the given filename.

Usage:

If --yjit-exit-locations is passed, a file named “yjit_exit_locations.dump” will automatically be generated.

If you want to collect traces manually, call dump_exit_locations directly.

Note that calling this in a script will generate stats after the dump is created, so the stats data may include exits from the dump itself.

In a script call:

at_exit do
  RubyVM::YJIT.dump_exit_locations("my_file.dump")
end

Then run the file with the following options:

ruby --yjit --yjit-trace-exits test.rb

Once the code is done running, use Stackprof to read the dump file. See Stackprof documentation for options.

enable(stats: false, log: false, mem_size: nil, call_threshold: nil)

yjit.rb View on GitHub

          # File tmp/rubies/ruby-4.0.0/yjit.rb, line 48
def self.enable(stats: false, log: false, mem_size: nil, call_threshold: nil)
  return false if enabled?

  if Primitive.cexpr! 'RBOOL(rb_zjit_enabled_p)'
    warn("Only one JIT can be enabled at the same time.")
    return false
  end

  if mem_size
    raise ArgumentError, "mem_size must be a Integer" unless mem_size.is_a?(Integer)
    raise ArgumentError, "mem_size must be between 1 and 2048 MB" unless (1..2048).include?(mem_size)
  end

  if call_threshold
    raise ArgumentError, "call_threshold must be a Integer" unless call_threshold.is_a?(Integer)
    raise ArgumentError, "call_threshold must be a positive integer" unless call_threshold.positive?
  end

  at_exit { print_and_dump_stats } if stats
  Primitive.rb_yjit_enable(stats, stats != :quiet, log, log != :quiet, mem_size, call_threshold)
end

Enable YJIT compilation. stats option decides whether to enable YJIT stats or not. log decides whether to enable YJIT compilation logging or not. Optional mem_size and call_threshold can be provided to override default configuration.

stats:
- false: Don’t enable stats.
- true: Enable stats. Print stats at exit.
- :quiet: Enable stats. Do not print stats at exit.
log:
- false: Don’t enable the log.
- true: Enable the log. Print log at exit.
- :quiet: Enable the log. Do not print log at exit.

enabled?

yjit.rb View on GitHub

          # File tmp/rubies/ruby-4.0.0/yjit.rb, line 12
def self.enabled?
  Primitive.cexpr! 'RBOOL(rb_yjit_enabled_p)'
end

Check if YJIT is enabled.

log

yjit.rb View on GitHub

          # File tmp/rubies/ruby-4.0.0/yjit.rb, line 206
def self.log
  return nil unless log_enabled?

  Primitive.rb_yjit_get_log.map do |timestamp, path|
    [Time.at(timestamp), path]
  end
end

Return an array of log entries. Return nil when option is not passed or unavailable.

log_enabled?

yjit.rb View on GitHub

          # File tmp/rubies/ruby-4.0.0/yjit.rb, line 22
def self.log_enabled?
  Primitive.rb_yjit_log_enabled_p
end

Check if --yjit-log is used.

reset_stats!

yjit.rb View on GitHub

          # File tmp/rubies/ruby-4.0.0/yjit.rb, line 32
def self.reset_stats!
  Primitive.rb_yjit_reset_stats_bang
end

Discard statistics collected for --yjit-stats.

runtime_stats(key = nil)

yjit.rb View on GitHub

          # File tmp/rubies/ruby-4.0.0/yjit.rb, line 188
def self.runtime_stats(key = nil)
  raise TypeError, "non-symbol given" unless key.nil? || Symbol === key

  Primitive.rb_yjit_get_stats(key)
end

Return a hash for statistics generated for the --yjit-stats command line option. Return nil when option is not passed or unavailable. If a symbol argument is provided, return only the value for the named stat. If any other type is provided, raises TypeError.

stats_enabled?

yjit.rb View on GitHub

          # File tmp/rubies/ruby-4.0.0/yjit.rb, line 17
def self.stats_enabled?
  Primitive.rb_yjit_stats_enabled_p
end

Check if --yjit-stats is used.

stats_string

yjit.rb View on GitHub

          # File tmp/rubies/ruby-4.0.0/yjit.rb, line 196
def self.stats_string
  # Lazily require StringIO to avoid breaking miniruby
  require 'stringio'
  strio = StringIO.new
  _print_stats(out: strio)
  strio.string
end

Format and print out counters as a String. This returns a non-empty content only when --yjit-stats is enabled.