I think you're getting Nagled. From the wikipedia article: "With both algorithms enabled, applications which do two successive writes to a TCP connection, followed by a read, experience a constant delay of up to 500 milliseconds, the 'ACK delay'."

Adding setsockopt($sock, IPPROTO_TCP, TCP_NODELAY, 1); just after your accept seems to clear the delay in the two print case, confirming the guess.

Of course, this now raises two other questions:

  1. Why does closing the socket in the parent make a difference?
  2. Why doesn't this trigger on windows (which surely has these basic TCP algorithms enabled by default too?)

In reply to Re: I know two prints are slower than one, but 200x slower?!?!? by jbert
in thread I know two prints are slower than one, but 200x slower?!?!? by rsmah

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