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Mail Archives: djgpp/1997/11/03/23:43:04

Date: Tue, 4 Nov 1997 12:39:58 +0800 (GMT)
From: Orlando Andico <orly AT dilnet DOT upd DOT edu DOT ph>
To: "John M. Aldrich" <fighteer AT cs DOT com>
cc: djgpp AT delorie DOT com
Subject: Re: DJGPP and Linux
In-Reply-To: <345ECC69.7FA4@cs.com>
Message-ID: <Pine.SGI.3.96.971104123703.14771B-100000@gibson.eee.upd.edu.ph>
MIME-Version: 1.0

On Tue, 4 Nov 1997, John M. Aldrich wrote:

..
> - Code which, under DOS, requires switches from protected mode to real
> mode (some interrupts, BIOS functions, etc.) will run faster under
> Linux, because it is a native pm environment; no mode switching is
> required.
> 
> - Programs will load faster under Linux because of significantly reduced
> overhead to enter protected mode and set up the required DPMI
> environment.  Linux also features shared libraries, as I understand, so
> this may further reduce loading time.
> 
> However, since the time-critical portions of the code are running on the
> same CPU and created by essentially the same compiler, there shouldn't
> be any noticeable speed difference.
> 
> If anybody knows different, please correct me.  :)

There IS one caveat: because Linux is a classical multitasking system,
each process CAN be suspended for an indefinite amount of time. For
example, if it's swapped out. And there isn't a way to "lock" a process in
physical memory, so if you're using something like an realtime event
handler under Linux (or UNIX generically) you might lose events. There are
several ways to fix this: use a realtime UNIX (e.g. LynxOS or QNX); use
high-priority/realtime threads (i.e. in Sun Solaris); or use realtime
Linux (RTLinux) which features microsecond-level response to system
events (at the expense of totally messing up the scheduler for
normal-priority programs).


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Orlando Alcantara Andico              Email: orly AT dilnet DOT upd DOT edu DOT ph
ICBM:  14 30 00 N  120 59 00 E               POTS:  (+632) 932-2385
"If I shed a tear I won't cage it, I won't fear love, and if I feel
 a rage I won't deny it, I won't fear love."      - Sarah Mclachlan

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