Path: utzoo!utgpu!water!watmath!clyde!bellcore!faline!thumper!ulysses!andante!princeton!udel!gatech!purdue!decwrl!ucbvax!RICHTER.MIT.EDU!krowitz
From: krowitz@RICHTER.MIT.EDU.UUCP
Newsgroups: comp.sys.apollo
Subject: locking object info physical memory
Message-ID: <8805122134.AA04356@richter.mit.edu>
Date: 12 May 88 21:34:42 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 28
Posted: Thu May 12 17:34:42 1988

I'm writing a device driver for a printer that has a high data
rate and no internal buffer. In order to send the data to the
printer at a high-enough rate, I format the entire page in a
buffer (a Pascal array) before starting the data transfer. The
problem I'm having is that the buffer is large (up to 2 MB) and
the virtual memory system pages the buffer out to the disk as I
fill it with the data -- when I begin the data tranfer I most of
the buffer is out on the disk, and the page faulting needed to
bring it back into physical memory interrupt the transfer of the
data to the printer which, in turn, leaves horizontal streaks
across the page at the places where the data transfer got interrupted.

Here's my question: is there some way of locking an array, or some
arbitrary piece of address space, into *physical* memory? The
MS_$ calls and RWS_$ calls talk about mapping things into the
*virtual* address space and talk about "locks", but these seems
to be locks on the access to the object. No mention is made of
physical vs. virtual memory. Does anyone have an info which
could help me on this?


 -- David Krowitz

krowitz@richter.mit.edu   (18.83.0.109)
krowitz%richter@eddie.mit.edu
krowitz%richter@athena.mit.edu
krowitz%richter.mit.edu@mitvma.bitnet
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