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To:	Paul Haahr <haahr@jivetech.com>
In-Reply-To: <cUtYiM7MbD@iadd.jivetech.com>
Cc:	rc@hawkwind.utcs.toronto.edu
Subject: Re: Dynamically loading readline on demand (was Re: rc futures)
From:	Tim Goodwin <tjg@star.le.ac.uk>
Message-ID: <vjsAAPhNfzhvHg8A@ltsun0.star.le.ac.uk>
Date:	Fri, 14 Jan 2000 11:26:20 -0500

> > I took an rc script that does nothing (makes no system calls) except
> > fork() and wait() 10000 times.
> 
> Are you sure it doesn't exec at all?

You tell me.

    for (i in 0 1 2 3 4 5 6 7 8 9)
    ...
    for (m in 0 1 2 3 4 5 6 7 8 9)
    @{ ~ 0 0 }

According to strace on my Linux box, each loop calls fork(), close(),
rt_sigaction() twice, _exit(), and wait().

> > ([...]  Why does dynamic linking increase the user time?

>                             The short answer is ``because dynamic
> linking is done with user-space code.'')

Yeah: in crt0.  But (I'm sure) that isn't involved here.  I'd expect
fork() to take more *system* time (since there are more MAP_SHARED page
table entries to fiddle with), but I don't understand the increase in
user time.

> I disagree.  Overall system resource consumption still goes down with
> dynamic linking and loading.  If a system is set up to use dynamic
> linking by default, why should rc override that?

You're right.  I wish you'd stop doing that :-).

Forcing static linking down people's throats is Not Nice.  Particularly
because (at least with the present setup) it's dead easy to turn static
linking on, but it would be quite hard to turn it off.  (For comparison,
see how easy it isn't to turn off `-Wall' if you're using gcc.)

I still intend to advocate it in the INSTALL document, though.

Tim.