From: "Brian F. Feldman" <green@...>
Date: 2001-11-06T00:00:58+09:00
Subject: [ruby-talk:24393] Re: Problem with readline and select

Rik Hemsley <rik@kde.org> wrote:
> The following program takes ~6s to complete when using readline in the
> main thread. It takes ~0s to complete when using sleep.
> 
> Some kind of clash between readline and IO.pipe/select ?
> 
> Ruby from CVS, checked out a couple of days ago.

That is quite correct.  The libreadline has its own timing internally 
required to detect the difference between multiple keypresses and a key 
generating a multiple-byte sequence.  I notice a very similar increase in 
latency when using irb as a readlineified front-end to a heavily-threaded 
server of mine.  If you reduce the select(2) timeout in libreadline itself, 
you'll get back your lower latency.

The other easy solution is to not use  libreadline, or fork off a child to
do the real work and have a front end that uses a pipe for the single
purpose of calling readline and passing back and forth what the user types
and backend prints.

-- 
 Brian Fundakowski Feldman           \  FreeBSD: The Power to Serve!  /
 green@FreeBSD.org                    `------------------------------'