begin
       require "io/nonblock"
       r, w = IO.pipe
       w.nonblock = true
       w.write_nonblock("a" * 100000)
       w.nonblock = false
       t1 = Thread.new { w.write("b" * 4096) }
       t2 = Thread.new { w.write("c" * 4096) }
       sleep 0.5
       r.sysread(4096).length
       sleep 0.5
       r.sysread(4096).length
       t1.join
       t2.join
     rescue LoadError
     end