Benchmark script for TailwindMerge::Config merging memory leak

benchmark_memory_leak.rb

# frozen_string_literal: true

# To run this script from the tailwind_merge repository, use:
# `ruby -Ilib bench_memory_leak.rb`

require "objspace"
require "tailwind_merge"

ITERATIONS = Integer(ENV.fetch("ITERATIONS", "1000"))
PAYLOAD_SIZE = Integer(ENV.fetch("PAYLOAD_SIZE", "1024"))

def rss_kb
  status = File.read("/proc/self/status")
  status[/^VmRSS:\s+(\d+)\s+kB$/, 1].to_i
rescue Errno::ENOENT
  `ps -o rss= -p #{Process.pid}`.to_i
end

def format_kb_from_bytes(bytes)
  format("%.1f KB", bytes / 1024.0)
end

def format_mb_from_kb(kb)
  format("%.1f MB", kb / 1024.0)
end

def snapshot(label)
  GC.start(full_mark: true, immediate_sweep: true)

  {
    label: label,
    rss_kb: rss_kb,
    heap_live_slots: GC.stat[:heap_live_slots],
    total_allocated_objects: GC.stat[:total_allocated_objects],
    merger_instances: ObjectSpace.each_object(TailwindMerge::Merger).count,
    class_utils_instances: ObjectSpace.each_object(TailwindMerge::ClassGroupUtils).count,
    default_spacing_entries: TailwindMerge::Config::DEFAULTS[:theme]["spacing"].length,
    memsize_all: ObjectSpace.memsize_of_all,
  }
end

def print_snapshot(before, after)
  puts "#{before[:label]} -> #{after[:label]}"

  puts "RSS:                    #{before[:rss_kb]} KB (#{format_mb_from_kb(before[:rss_kb])}) -> " \
       "#{after[:rss_kb]} KB (#{format_mb_from_kb(after[:rss_kb])})  " \
       "delta=#{after[:rss_kb] - before[:rss_kb]} KB (#{format_mb_from_kb(after[:rss_kb] - before[:rss_kb])})"

  puts "heap_live_slots:        #{before[:heap_live_slots]} -> #{after[:heap_live_slots]}  " \
       "delta=#{after[:heap_live_slots] - before[:heap_live_slots]}"

  puts "memsize_of_all:         #{format_kb_from_bytes(before[:memsize_all])} -> " \
       "#{format_kb_from_bytes(after[:memsize_all])}  " \
       "delta=#{format_kb_from_bytes(after[:memsize_all] - before[:memsize_all])}"

  puts "allocated objects:      delta=#{after[:total_allocated_objects] - before[:total_allocated_objects]}"
  puts "Merger instances:       #{before[:merger_instances]} -> #{after[:merger_instances]}"
  puts "ClassGroupUtils:        #{before[:class_utils_instances]} -> #{after[:class_utils_instances]}"
  puts "DEFAULT spacing length: #{before[:default_spacing_entries]} -> #{after[:default_spacing_entries]}"
end

def build_mergers
  ITERATIONS.times do |i|
    custom_scale = "custom-space-#{i}-#{"x" * PAYLOAD_SIZE}"

    merger = TailwindMerge::Merger.new(
      config: {
        theme: {
          "spacing" => [custom_scale],
        },
      },
    )

    # Exercise the custom theme path, then drop the local reference.
    merger.merge("p-1 p-#{custom_scale}")
  end
end

before = snapshot("before")
build_mergers
after = snapshot("after")

print_snapshot(before, after)