I use LuxRender 0.9 only with Reality2 plugin for Daz Studio4 (Reality2 update 184.108.40.206).
I have an iMac 24" Intel Core 2 duo with 4Gb Ram and an ATI Radeon HD4850 graphic card, with OS 10.6.8. I never use GPU acceleration with LuxRender as it seems it is not supported by my graphic card.
When I started using LuxRender, about two months ago, everything seemed to work fine, so I didn't pay much attention to the parameters. Rendering times were long (from 12 to 20 hours for a final render, depending on the complexity of the scene and the lighting) but on the whole acceptable, and the results quite fine. Above all, I was able to judge if the render conformed my expectations just after 10÷15 minutes from its start.
After a while I had a dramatic slow down in render times: I can't say if I made something wrong without being aware, however was not able to put things back in the proper way, not even reinstalling LuxRender and Reality from scratch.
So I started making some experiments step by step, registering all the statistic parameters, especially kC/s. I noticed than, whilst before the slow down the resource allocation was very quick and after starting the render LuxRender got the standard kC/s almost immediately, now the time of the resource allocation was much longer (the computer seems to «suffer» for some time, using all its resources to get the render start), and the render always started with something about 100 C/s (note: C/s, not kC/s), improving progressively but slowly in a very long time.
Next step I downloaded 5741_luxrender_osx64_1-19-2011 (but it was january 2012!) version, installed it (before I used the standard version LuxRender_0.9dev_universal), and things changed: not perfect, but much better. LuxRender still starts very slowly, beginning with 300÷500 C/s, however this 64 bit version speeds up progressively and in about an hour it reaches a reasonable speed. Look at the resume hereafter:
after 30': 30kC/s and 6 S/p
after 1h: 53 kC/s and 20 S/p
after 2h: 68 kC/s and 50 S/p
after 3h: 74 kC/s and 82 S/p
regimen: 80kC/s and about 30 S/p per hour
Ultimately, I could be quite satisfied with these render times, which are almost the same I had for my renders before the slow down crisis. There is still a problem: now I have to wait from 30 minutes to 1h to possibly judge if the render conforms to my expectations. Moreover, not always things are so easy, depending on the lighting: sometimes the slow down comes back, especially if I try to adjust the lighting settings during the render.
So, if anyone has any idea and/or suggestion about this problem, its origin and how to solve it, he is welcome. If you need more info, just ask. As I said, I always use LuxRender in the simplest way (no GPU, no memory conservation, only render frame). Thanks for your time.