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From: "Andy Cave" <andy.cave@hamillroad.com>
To: "Edward Lam" <edward@sidefx.com>, <tiff@lists.maptools.org>
References: <200811192021.mAJKLM6d027313@tux.cubewerx.com>
	<49247B5F.20708@sidefx.com>
Subject: Re: [Tiff] Memory leak (TIFFOpen, TIFFReadTile)?
Date: Wed, 19 Nov 2008 20:56:32 -0000
Organization: Hamillroad Software
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FWIW We use our own file I/O with libtiff (like a lot of people - or so I 
get the impression) and that definitely does not use memory mapped IO; that 
causes too many issues. For anyone who does anything with image data, who 
therefore knows what they are doing (certainly more than the OS), reading & 
caching the data themselves is far more efficient (since they know what 
there are doing) than letting the OS 'guess'. If you use memory mapped IO 
you run the risk of running out of address space, the OS can end up paging 
other data out of memory which is more valuable (especially if you access 
the data once), etc... If you access the data more than once, you can 
arrange to cache that which you use more than once, or do other clever 
stuff, etc... Memory mapping was touted years ago as the solution for memory 
problems, but personally I've never been convinced.

Regards,

Andy.

----- Original Message ----- 
From: "Edward Lam" <edward@sidefx.com>
To: <tiff@lists.maptools.org>
Sent: Wednesday, November 19, 2008 8:47 PM
Subject: Re: [Tiff] Memory leak (TIFFOpen, TIFFReadTile)?


Maybe a pertinent question is whether anyone is using the default
TIFFOpen()? Maybe everyone opens their tiff file with the explicit flag
to not memory map. :)

-Edward

Craig Bruce wrote:
> Frank Warmerdam <warmerdam@pobox.com> wrote:
>
>> I'm not getting any strong mandate to change the current behavior so
>> I'm inclined to do nothing - my usual preference.
>
> My position is that it should be changed because memory-mapped I/O is
> a bit unusual and casual TIFF-lib users won't be expecting it or its
> associated problems with large files.  Though, of course, I have found
> a work-around for my own TIFF-lib usage.
>
> --------------------------+----------------------+--------------------------
> Dr. Craig S. Bruce        | Ph 819-771-8303 x205 |             CubeWerx 
> Inc.
> Senior Software Developer |   Fax 819-771-8388   |  Gatineau, Québec, 
> Canada
> csbruce@cubewerx.com      |  http://csbruce.com/ | 
> http://www.cubewerx.com/
> --------------------------+----------------------+--------------------------
>      "Man will never be free until the last king is strangled with the
>                   entrails of the last priest." -- Diderot
> _______________________________________________
> Tiff mailing list: Tiff@lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/tiff
> http://www.remotesensing.org/libtiff/

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