[osg-users] [Not OSG related question] Virtual memory management on Windows

[Gordon Tomlinson]

Hi 

 

There's many issues why you will struggle with this and no it's not just a
windows issues it effects other OS's some do a better job off moving the
issues forward but they will still crop up

 

Simplest solution is to go to a 64bit OS with a good 8gb or more.

 

There is another limitation you will hit on 32bit windows is you can only
have an address space per process of 1.8gb , other OS's such as Unix's and
Linux's do a much better job and get you near the true 32bit limit

 

Another problem is that you need a contiguous memory area for malloc/new on
windows  this is a  big problem , 

 

Some of the reasons why this is an issue is that Windows has already eaten
up a chunk of the available memory, not only with programs , services ,
dll's being loaded they sadly  simply  don't get then next serial  memory
address, they may be load smack bang in the middle of the address space, so
straight away that can l half the size of the max malloc/new you can do. As
you load more programs more dll's the longer windows is running the more
fragmented the memory will get and the smaller the max malloc/new can create
will get lower, the MAC's OS's are the best at handling this sort of thing
and Linux is typically better than window's

 

What you can try is all the normal traditional tips, only run [processes,
services that absolutely need to  etc see
http://www.vis-sim.com/vega/vegafaq1.htm#f39 ( needs modernizing but the
gist is valid)

 

This use be a big problem back in the heyday of IRIX, it would load is
system SO's(dll's)  smack bang in the middle of memory the same for
programs. What had to be do there was to force the system to load its libs
either high or low and you has to rebase the loading address of all the SO's
your program used.

 

You can do a similar thing in Windows and for all your dll's to re-base and
control were they load. If you do that the final  trick is that as some as
your application starts you need to create the large memory stuff straight
away, otherwise your address space will get fragmented and your back to
square one

 

At my company we have to handle multi-terra byte imagery and have to use
processes like I have described, so it can be done. you just need an
engineer that knows this hard stuff, thankfully  we have an engineer that
does ;) and no you cannot have him ;)

 

 

 

__________________________________________________________
Gordon Tomlinson 

Email   :  <mailto:gordon at GordonTomlinson.com> gordon at GordonTomlinson.com
YIM/AIM : gordon3dBrit
MSN IM  :  <mailto:gordon3dBrit at 3dscenegraph.com>
gordon3dBrit at 3dscenegraph.com
Website :  <http://www.vis-sim.com> www.vis-sim.com
<http://www.gordontomlinson.com> www.gordontomlinson.com 

__________________________________________________________

 

From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of David Callu
Sent: Wednesday, June 25, 2008 3:05 PM
To: OpenSceneGraph Users
Subject: Re: [osg-users] [Not OSG related question] Virtual memory
management on Windows

 

power linux Serge ;-).

Regards
David Callu

2008/6/25 Serge Lages <serge.lages at gmail.com>:

Hi all,

I have a question not related to OSG but I can't find any answer, and this
is something that some of you probably knows. That's why I try here to find
some help.

Here is my problem : I have a big image database with some images larger
than 1.5Go uncompressed, and I fail to load them (Win XP SP2 32bits with
Visual Studio 8). My computer has 3Go of virtual memory and the option /3GB
is activated on the system. In this document (page 13) :
http://actes.sstic.org/SSTIC05/Vulnerabilites_et_gestion_des_limites_memoire
/SSTIC05-article-Delalleau-Vulnerabilites_et_gestion_des_limites_memoire.pdf
It says it's not possible to allocate more than 1.3Go in one call, and it's
actually the limit where it crashs. If I do 2 allocations of 1Go each, it
works, but 1 allocation of 1.4Go crashs...

Has someone any idea if it's possible to change this limit ? My only hope
will be to make smaller images, or even to develop under Linux ? :)
Thanks in advance !

-- 
Serge Lages
http://www.tharsis-software.com 
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