Memory size of Ractor vs Thread vs Fiber

concurrency.md

On my machine (Apple M4 Max):

• 53 KB per ractor
• 71 KB per thread
• 48 KB per fiber

And performance overhead (10k simple, linear return value):

             user     system      total        real
ractor   0.783589   0.368951   1.152540 (  1.074543)
thread   0.917771   0.449474   1.367245 (  1.198391)
fiber    0.009250   0.017416   0.026666 (  0.026904)

concurrency.rb

# frozen_string_literal: true
Warning[:experimental] = false

def self.get_memory
  GC.start
  `ps ax -o pid,rss | grep -E "^[[:space:]]*#{$$}"`.strip.split.last.to_i
end

args = ARGV.any? ? ARGV : ["ractor", "thread", "fiber"]

args.each do |arg|
  case arg
  when "ractor" then factory = proc { Ractor.new { sleep } }
  when "thread" then factory = proc { Thread.new { sleep } }
  when "fiber"  then factory = proc { Fiber.new { Fiber.yield }.resume }
  else
    warn "Unknown argument: #{arg}", "Usage: #{$PROGRAM_NAME} [ractor|thread|fiber]"
    exit 1
  end

  first  = get_memory
  result = 1000.times.map(&factory)
  last   = get_memory

  puts "#{(last - first) / result.size} KB per #{arg}"
end

require "benchmark"

count = 10_000

Benchmark.bmbm do |x|
  x.report("ractor") { count.times { Ractor.new { true }.value } } if args.include?("ractor")
  x.report("thread") { count.times { Thread.new { true }.value } } if args.include?("thread")
  x.report("fiber")  { count.times { Fiber.new { true }.resume } } if args.include?("fiber")
end