Can't get more than 6000 r/s

pipeline_test.rb

require 'net/http/pipeline'


def runit
  Net::HTTP.start 'localhost', 7474 do |http|
    http.pipelining = true

    reqs = []
  
    6000.times do
      reqs << Net::HTTP::Get.new('/')
    end
    count = 0
    http.pipeline reqs do |res|
      count+= 1 if (res.code == "200")
    end
  
    puts count
  end
end

puts "Started At #{Time.now}"
start = Time.now
count = 0
arr = []

10.times do |i|
   arr[i] = Thread.new {
      runit
      count += 1
   }
end

arr.each {|t| t.join; }
puts "count = #{count}"
puts "End at #{Time.now}"
p Time.now - start 

Started At 2014-04-11 10:05:44 -0500
6000
6000
6000
6000
6000
6000
6000
6000
6000
6000
count = 10
End at 2014-04-11 10:05:55 -0500
10.861858