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Subject:	RE: question about shared memory in the cygwin daemon
Date:	Wed, 4 Aug 2004 14:53:26 -0400
Message-ID:	<A5F4BEF689E6FA47BC56396D0B9F15057F15D7@daytonmsg2k.aero.ball.com>
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From:	"Clarke, Trevor" <tclarke AT ball DOT com>
To:	<cygwin AT cygwin DOT com>
X-OriginalArrivalTime:	04 Aug 2004 18:53:28.0167 (UTC) FILETIME=[5432BF70:01C47A54]

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We currently run on 32bit windows and 32/64but solaris with near future
plans to run on 64bit windows. The product is for a specific client so
we can assume 4gb or more of physical ram.

As for Matlab, the problem is that the library routines for embedding
matlab spawn a separate process and use IPC to talk to it (COM under
windows I believe) so data sent is copied to another address space.

Again, we can assume sufficient RAM for a data set and even if a page is
swapped out to disk, it should be data that's not actively processing so
the impact on performance should be less than processing directly on
disk.
------------------------------
Trevor R.H. Clarke
tclarke AT ball DOT com
Ball Aerospace & Technologies Corp

-----Original Message-----
From: Dave Korn [mailto:dk AT artimi DOT com]=20
Sent: Wednesday, August 04, 2004 1:37 PM
To: cygwin AT cygwin DOT com
Subject: RE: question about shared memory in the cygwin daemon

> -----Original Message-----
> From: cygwin-owner On Behalf Of Clarke, Trevor
> Sent: 04 August 2004 17:54

> I'm currently developing image processing software which will=20
> use matlab
> as a "plugin" for interactive processing. The problem is, matlab, when
> called from another program, spawns a separate matlab engine process.
> The data we are working with can get very large (4gb+) so we=20
> can't pass
> copies of it around. We are looking at using cygwin's shared memory
> functionality to get around this on windows (NT derivatives only).

  Your data won't even fit into a 32-bit address space, so I don't think
shared memory is going to help you.

  Even if you're using an x86-64 platform, you have to bear in mind that
you've got a virtual memory system there.  If your data set is 4Gb, and
your
system RAM is < 4Gb, then even mapping it into shared memory between
processes will involve it going out to disk and back when the pagefile
starts swapping.

  Is there not a library version of matlab you can link to your
application
and call into from the same process space?


    cheers,=20
      DaveK
--=20
Can't think of a witty .sigline today....


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