Mail Archives: djgpp/1995/08/21/20:18:36
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From: | gantose AT lerc DOT nasa DOT gov (Dave Gantose)
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Newsgroups: | comp.os.msdos.djgpp
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Subject: | Re: Please define "locking"
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Date: | Mon, 21 Aug 95 18:32:21 GMT
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Organization: | ADF, Inc.--NASA Lewis, Cleveland, OH
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Lines: | 41
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Nntp-Posting-Host: | babar.lerc.nasa.gov
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To: | djgpp AT sun DOT soe DOT clarkson DOT edu
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Dj-Gateway: | from newsgroup comp.os.msdos.djgpp
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Thank you to Charles Sandmann who wrote:
>(...)
>So, you don't want anything you will touch in a hardware interrupt routine
>to every get paged out to disk (including the code,data,stack). If you have
>enough memory on your machine that you never page (or have disabled virtual
>memory) this is not a problem. If you do page, the DPMI page locking
>services are a way to tell the paging mechanism to never take those pages
>out of memory, and avoid the problem.
I should have mentioned that I am programming for an embedded processor that
will not have access to a hard drive, so I guess that if my programs don't die
of memory exhaustion, then they are OK. However, the machines I develop and
test upon DO have hard drives, so how would I disable virtual memory on them
so that I don't have to deal with this?
>(...)
>Since it's very difficult to track down every memory address you might touch
>in C, this is why you start worrying about GAS code so you have control over
>the location of the code and data so you know exactly what to lock. The
>simple fix is to buy more memory (for everyone :-) so paging is eliminated.
And thanks to Mat Hostetter who wrote:
>I've written DPMI interrupt handlers that properly lock memory.
>Here's a quick, imprecise oversimplification of the issues involved
>(...)
>V2 is rock solid if you play by the rules. Unfortunately, those rules are
>tricky.
Even though I do not want to deal with this for my current application, I
would still like to know how to do it right. Do either of you (or anyone else
reading this) have a favorite example you could point me to? (I already have
downloaded--but not yet studied--the Soundblaster library by Joel Hunter.)
=============================================================================
Dave Gantose
ADF, Inc.
2001 Aerospace Pkwy. phone: (216)977-1376
Brook Park, OH 44142 email: Gantose AT lerc DOT nasa DOT gov
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