How to compress .tga file?

Hi,
I am using 3ds max modeller and oFusion exporter feeding my ogre app.
But I found imported into my app, it runs rather slow. I examine the exported files and found there are so many .tga files, and they are normally pretty large. I have always been believing in ogre's effeciency, so I think the problem is, after so many large texture resource attached into one model, it consumes lots of ram and wastes my precious processing power on page swapping. So I think texture compression might be a good solution, but I really dont know how to achieve it.
Is there someone would give me some suggestion? If ogre have some build-in method, or I should pre-process it off-line? And if it is done, will decompression procesure be expensive?

Use the NVidia DDS tools to convert your tgas to DDS files with compression

If you use DDS then there is no software decompression (its being made at hardware level, in the GPU)

If you use any other regular image compression format (jpg, compressed tga or other) then you are just saving disk space, not memory space as they are decompressed before sending to the gpu mem

To optimize the texture space use "texture atlas"

And use layers if possible (multiple textures in a pass) to avoid big sized textures with all of the details on it, for example to have light and shadow information in a small texture, decal on another bigger texture, and the diffuse or color texture on other