Top File-Backed Memory Mappings (Ruby script)

cached_mappings.rb

#!/usr/bin/env ruby

require 'optparse'

def parse_smaps(pid)
  smaps_path = "/proc/#{pid}/smaps"
  unless File.exist?(smaps_path)
    abort("Error: #{smaps_path} not found. Are you root?")
  end

  data = Hash.new { |h, k| h[k] = { 'Rss' => 0, 'Shared_Clean' => 0, 'Private_Clean' => 0 } }
  current_mapping = nil

  File.foreach(smaps_path) do |line|
    if line =~ /^([0-9a-f]+)-([0-9a-f]+)\s.*\s(\/.+)$/
      current_mapping = $3
    elsif line =~ /^(Rss|Shared_Clean|Private_Clean):\s+(\d+) kB/
      key, value = $1, $2.to_i
      data[current_mapping][key] += value if current_mapping
    end
  end

  data
end

def print_top_mappings(data, limit)
  sorted = data.sort_by { |_, mem| -(mem['Shared_Clean'] + mem['Private_Clean']) }

  total_clean_kb = 0
  total_rss_kb = 0

  puts "\nTop #{limit} file-backed memory mappings (by cached memory):"
  puts format("%12s  %10s  %s", "Memory (MB)", "Rss (MB)", "Mapping Path")
  puts "-" * 60

  sorted.first(limit).each do |path, mem|
    clean_kb = mem['Shared_Clean'] + mem['Private_Clean']
    rss_kb = mem['Rss']
    total_clean_kb += clean_kb
    total_rss_kb += rss_kb

    puts format("%12.1f  %10.1f  %s", clean_kb / 1024.0, rss_kb / 1024.0, path)
  end

  puts "-" * 60
  puts format("%12.1f  %10.1f  TOTAL (Top #{limit})", total_clean_kb / 1024.0, total_rss_kb / 1024.0)
end

if ARGV.length < 1
  puts "Usage: ruby cached_mappings.rb <pid> [top_n]"
  exit 1
end

pid = ARGV[0]
top_n = (ARGV[1] || 10).to_i

mem_data = parse_smaps(pid)
print_top_mappings(mem_data, top_n)