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From: jfh@rpp386.cactus.org (John F Haugh II)
Newsgroups: comp.unix.internals
Subject: Re: POSIX bashing (readline bashing)
Message-ID: <19143@rpp386.cactus.org>
Date: 2 Apr 91 05:59:48 GMT
References: <3446@unisoft.UUCP> <15621@smoke.brl.mil> <70319@brunix.UUCP> <27F43DE6.4B53@wilbur.coyote.trw.com> <564@bria> <70433@brunix.UUCP>
Reply-To: jfh@rpp386.cactus.org (John F Haugh II)
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In article <70433@brunix.UUCP> cgy@cs.brown.edu (Curtis Yarvin) writes:
>Certainly.  On a 100-user mainframe, canonical mode is not a marginal
>optimisation.  My point was that the good 'ol 9600 bps terminals & large
>time-sharing systems are likely to pass away soon, except in heavy-duty
>transaction processing environments.  Networking technology (in my opinion)
>has become simple, reliable, and effective enough that a mainframe is rarely
>the most cost-effective option when purchasing a new system.

There are no "100-user mainframes".  The S/6000, which is a microcomputer
by all accounts, supports well over 100 users.  The 3090/600E I use for
problem tracking supports about 4,000 users total, with the particular
virtual machine I access most running close to 1,000 simultaneous sessions.
Other virtual machines on that CPU run well over 2,000 simultaneous
sessions.

>Typing away on what?  sh? ed?  If they're using a shell with editable
>history (as most prefer), or they're editing a file, they're in raw mode.
>If you have such a mongo mainframe around, and you have kmem privileges, it
>might be interesting to run some tests and see exactly how much time is
>spent in canonical mode.

Block mode terminals and "cooked" mode tty I/O were developed specifically
to get around the issues of interrupt service.  Deferring as much of the
processing to as late a time as possible lets you do it all at once, without
running in circles performing needless context switches.  Using the GNU
readline() code will aggrevate matters further because it is a PIG.

You don't need to snoop about too hard - just turn profiling on for your
kernel (for System V types).
-- 
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