bm.rb

require 'benchmark'
require './puppet/lib/puppet/util/puppetdb/char_encoding'
include Puppet::Util::Puppetdb::CharEncoding

random_bytes = File.read('/dev/urandom', 10)
strings = 5.times.map { |i|  ("0" * 1024 * (i+1)*100 + random_bytes).force_encoding('UTF-8') }

Benchmark.bm(1) do |x|
  x.report('str.index') { strings.last.index(DEFAULT_INVALID_CHAR) }
  strings.each do |str|
    x.report("all_indexes_of_char (#{str.size} bytes)") do
      Puppet::Util::Puppetdb::CharEncoding.all_indexes_of_char(str, DEFAULT_INVALID_CHAR)
    end
  end
end

results.txt

        user     system      total        real
str.index  0.000000   0.000000   0.000000 (  0.000060)
all_indexes_of_char (102408 bytes)  0.250000   0.000000   0.250000 (  0.259929)
all_indexes_of_char (204808 bytes)  0.970000   0.010000   0.980000 (  0.977001)
all_indexes_of_char (307208 bytes)  2.240000   0.010000   2.250000 (  2.264098)
all_indexes_of_char (409608 bytes)  4.180000   0.010000   4.190000 (  4.206656)
all_indexes_of_char (512008 bytes)  6.740000   0.010000   6.750000 (  6.779366)