[Gimp-user] Tweaking performance

[<jfrazierjr nc rr com>]

Ok.. so I am working on a large image and want to see if I can increase performance speed any.  I knew things 
would be slow, but was hoping I could get a bit better than what I currently have.  The image will be a 
map(as in fantasy world map) I want to print(will scale down for web version to .jpeg), 36x24 inches @300 
DPI, so 10800x7200 resolution(ie, poster print size).   

I have a fresh install of Linux Mint 11 on a laptop which is about two years old.  I don't remember the full 
PC specs off the top of my head though but is was a mid-high end range gaming Laptop(so probably in the top 
70%-80% of "best" available laptop hardware specs at the time of purchase).  

What I do know off the top of my head:

Machine: 
multiple partitions
20GB Linux swap
Mint installed to single partition 190GB out of the entire HD's 500GB(both /home(location of the xcf file) 
and /tmp are on the same partition.  
6GB RAM (8GB max)
multiple USB 2 ports
1 eSATA port
Wacom bamboo tablet
video card is (I BELIEVE) a GTX 200M 


Gimp:
built from source (git) as of umm... Friday night(or so)
Currently, I have my tile-cache size set to 5GB

I typically have 3-6 chrome browser windows open and perhaps 1-2 open directory folders, but other than that, 
there are few applications running other than those(occasionally Thunderbird).

Currently, the file opens up around 4.5 GB in memory, with spikes up to 10GB so far that I have seen.  I have 
about 15 layers so far, with about half of those using a layer mask.   Most of the layers are transparent at 
this point, with a few being full color with layer masks to define geological features(grassy plains, desert, 
etc).   

I have yet to add the additional layers needed to represent mountains and forests(at least 4 layers each, 
line-work, color, highlights, and lowlights, so min 8 layers for that) as well as several layers for some 
type of desert texture, labels(4-5 layers), and likely a compass rose and a Cartouche of some type(likely 4-6 
layers for shape/color as well as 2-4 text sections).  So all together, this will likely encompass around 
35-40 layers when completed(if I can get that far!!!). 


So, are there any suggestions you guys might make?  As slow as it is currently, I don't know if I will even 
be able to get anywhere near to the number of layers I expect to need.  Should I just give up on such a large 
image and reduce the scale or is there any additional tweaks I can make?  Will adding a eSATA or USB2 drive 
to hold the the /tmp help at all?  I this was a desktop, I could easily just slap another Harddrive(or two) 
in and have different read/writes working in parallel(ie, /tmp and swap on a separate physical drive), but I 
don't have that luxury with a Laptop... Would adding an additional 2GB make a noticeable(as in very 
noticeable) difference?

I appreciate any suggestions you guys might have.  Please let me know if there is any additional 
information(ie, L2 Cache, Processor, etc) and I can get that info later tonight.... though of course those 
are things I cannot change...

Joe