Ger wrote:
> Tom Austin <taustin> wrote:
> 
>> It looks like you know what you are doing, but here are some things I
>> have run across regarding memory - based on 32 bit systems.
>>

And, yes, you do know what you are doing :-)


>> A single application (thread) is limited to using 2GB or 3GB depending
>> on your OS and settings within the OS.
>>
>> I have found that typically in 
>> Windows the limit is 2GB and Linux is 3GB (tho these can be affected by
>> OS settings).  I have run into these ceilings myself running various
>> applications.  I have found no way of allowing for more memory usage in
>> a 32bit system.  I set up 16GB swap once only to have the application
>> crash at 3GB.
> 
> This is most likely due to limits inside the application, not the OS
> 

Not on a 32 bit system where accessing that much memory is a problem.
Lots of research and trial and error have shown me this.

>> Also, the OS might be capable of using much more than 2GB (or 3GB), but
>> it must be in the form of separate applications (or threads).  It might
>> be entirely possible to run (3) 2GB applications - 
> 
> I'm currently running 2 renders of 2.5 Gb each, alongside the usual bunch of
> office thingies, mail, news, browsers, photo editors, etc etc.
> Swap space usage is upto 3.5 Gb now.
> 
> 
> Correct, when you go above 3 Gb you will need to change the kernel to the
> "big" version allowing for more internal memory, and this is where my
> problems started. It turned out that something fishy had happened when I
> switched kernels.
> 

That's what it started to look like to me when I was replying to your 
message earlier.  That running 64 bit should not have any problems, but 
something is still holding you back.  And a misconfiguration in the 
kernel could do that :-)


>> If your system is 64 bit, it could be that something is still limiting
>> it to using 32 bit memory addressing.
> 
> Not under Linux, I don't know about 64bit Windows
> 

A misconfiguration could hold you back - what I was getting at.


>> Now, my experience is only with a 32 bit system.  I understand that 64
>> bit systems have much different limitations, but I have no experience
>> with them.  I hope that this sheds a bit of light for you.
>>
> 
> With the arrival of 64 bit systems the phrase "The sky's the limit" has been
> superseded with "The sky's just the beginning" :)
> 

Every once in a while we throw something at a computer that is just too 
much for it.  I know of two incidents where I've needed more than 2GB of 
memory.  One was due to a bug in AutoCAD - which I now have a workaround 
for.. the other is aligning 50+ 3D data scans (2 million data points 
each) which we do in sections.

Maybe our next computer will be a 64 bit system so that we can see how 
it affects our work flow.


LAter... Tom

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