How to quickly output a LARGE amount of data to STDOUT in Ruby?

Question

ruby

Good day.
The challenge is to quickly print hundreds of millions of lines to STDOUT.
The code is executed in a docker container with 2 cores and 4 GB of RAM.
Ruby 2.7.0

Now pseudo-specific:
There are several files (each from 2,000,000 to 3,000,000 lines) that are read line by line, each line is output from 10,000 to 150,000 times.

def print_gen(line)
  rand(10000..150000).times do
    $stdout.write(line)
  end
end

['1.txt', '2.txt', '3.txt'].each do |file|
  fork do
    File.readlines(file).each do |line|
      print_gen(line)
    end
  end
end
Process.waitall

Result of work:

time ruby start.rb > test.txt
real	1m13,236s
user	1m12,338s
sys	0m1,011s

wc -l test.txt
119245 test.txt

The profiler clearly shows the problem with IO.wait.
When using threads, the picture is similar.

How can you speed up the process?

Answer 1

What does the output to stdout have to do with reading the logs?
$stdout.write
The test is meaningless.
File.each_linemore efficient in memory consumption.