File reading benchmark

bmx.rb

#! ruby19

require 'benchmark'

REP = 10
BS = 1024

files = []

at_exit do
  files.each {|name| File.delete(name) rescue nil}
end

[100, 1024*1024, 1024*1024*100].each do |s|
  name = "f-#{s}.bin"

  File.open(name, File::WRONLY | File::EXCL | File::CREAT | File::BINARY) do |out|
    data = (".".encode! 'binary') * 1024

    while s >= data.bytesize
      s -= out.write(data)
    end

    out.write(data[0, s])
  end

  files << name
end

Benchmark.bmbm 30 do |r|
  files.each do |name|
    r.report name + ' simple' do
      REP.times do
        File.open name, "rb" do |io|
          while b = io.read(BS)
          end
        end
      end
    end

    r.report name + ' smart' do
      REP.times do
        File.open name, "rb" do |io|
          b = ""
          while io.read(BS, b)
          end
        end
      end
    end

    r.report name + ' complete' do
      REP.times do
        File.open name, "rb" do |io|
          io.read
        end
      end
    end
  end
end

result.txt

Rehearsal -----------------------------------------------------------------
f-100.bin simple                0.000000   0.000000   0.000000 (  0.004000)
f-100.bin smart                 0.016000   0.000000   0.016000 (  0.005000)
f-100.bin complete              0.000000   0.000000   0.000000 (  0.008000)
f-1048576.bin simple            0.094000   0.046000   0.140000 (  0.133000)
f-1048576.bin smart             0.078000   0.016000   0.094000 (  0.100000)
f-1048576.bin complete          0.015000   0.031000   0.046000 (  0.054000)
f-104857600.bin simple          9.031000   3.875000  12.906000 ( 12.913000)
f-104857600.bin smart           5.766000   4.047000   9.813000 (  9.820000)
f-104857600.bin complete        0.609000   3.156000   3.765000 (  3.807000)
------------------------------------------------------- total: 26.780000sec

                                    user     system      total        real
f-100.bin simple                0.016000   0.000000   0.016000 (  0.007000)
f-100.bin smart                 0.000000   0.000000   0.000000 (  0.008000)
f-100.bin complete              0.000000   0.000000   0.000000 (  0.007000)
f-1048576.bin simple            0.093000   0.109000   0.202000 (  0.207000)
f-1048576.bin smart             0.078000   0.016000   0.094000 (  0.103000)
f-1048576.bin complete          0.000000   0.046000   0.046000 (  0.037000)
f-104857600.bin simple          8.594000   4.125000  12.719000 ( 12.760000)
f-104857600.bin smart           6.219000   3.500000   9.719000 (  9.721000)
f-104857600.bin complete        0.593000   3.125000   3.718000 (  3.778000)