From:	Kristian Hogsberg Kristensen <hogsberg AT cruzeiro DOT daimi DOT aau DOT dk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	exception processing overhead
Date:	22 Jan 1997 14:33:21 +0100
Organization:	DAIMI, Computer Science Dept. of Aarhus Univ.
Lines:	22
Message-ID:	<y6ysp3tu95q.fsf@cruzeiro.daimi.aau.dk>
NNTP-Posting-Host:	cruzeiro.daimi.aau.dk
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Hi,

I've been looking into the exception processing
code and setting the ds-limit to 0 in hw-interrupts
and then have the client code cause an exception
is a neat trick since you can transfer control
away from the handler with longjmp and (I guess)
dont need to lock the memory you access. As
such this technique is an attractive alternative to
the standard interrupt hooking mechanism (espcially
if locking all accessed memory is non-trivial). But I 
fear that there is a considerable overhead when
handling hw-interrupts this way. The processing on 
the client side I can figure out from the exception 
processing code, what I'm asking is: What is
the extra overhead in the DPMI-host (say, CWSDPMI) 
when using this technique? Could this be used for high
frequency timer interrupts?

thanks,
Kristian Hogsberg
hogsberg AT daimi DOT aau DOT dk

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