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Path: utzoo!attcan!uunet!ficc!peter
From: peter@ficc.uu.net (Peter da Silva)
Newsgroups: comp.lang.ada
Subject: Re: Ada vs C/UNIX / switching speeds
Summary: Apples and oranges.
Message-ID: <7103@ficc.uu.net>
Date: 25 Nov 89 18:39:13 GMT
References: <14042@grebyn.com>
Reply-To: peter@ficc.uu.net (Peter da Silva)
Organization: Xenix Support, FICC
List-Id: <comp.lang.ada>

> >  The following article relates to the recent discussion
> >  of Ada vs. UNIX/C and lightweight processes.  Notice the
> >  disastrous performance produced by UNIX/C relative to Ada.

Yeh. Since ADA shouldn't have to do more than a function call, a switch
in stack frames, and a return in the new stack frame... why is it so slow?

> >Sun 3/50 (UNIX) Function call    ~ 0.01 ms
> >Sun 3/50 (UNIX) Verdix Ada tasks ~ 0.3  ms
> >Sun 3/50 (UNIX) UNIX/C processes ~10.0  ms

I would have expected the ADA task switch to take no more than 0.05 ms
based on the speed of a function call. There's no MMU to deal with, a not
inconsiderable overhead. There's no switch between user and kernel mode.
There's none of the overhead that UNIX has to deal with. What's it doing,
dynamically rearranging priorities at context-switch time instead of when
you make a call or handle an external event?

Lester Buck: could yo do some estimates on the context switch time for
your C-threads routines? And has anyone done any realtime benchmarks on
the Amiga?
-- 
`-_-' Peter da Silva <peter@ficc.uu.net> <peter@sugar.lonestar.org>.
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