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