I have a simple scene with a cube and three light. I dont know why i see that my viewport so slow when i enable IPR render of Arnold 6 although i have a power computer with Dual xeon 2670 and dual Gefore 1070ti, pls see this video:
https://www.youtube.com/watch?v=6v74jqMOcQk&feature=youtu.be
Does lowering the number of render threads help? Try -2 threads, then -4, -8, etc. to see if it's an issue of your machine not having enough idle cores for both maya, other apps, and arnold.
https://docs.arnoldrenderer.com/display/A5AFMUG/Render+Settings
One other question: What version of Arnold are you using? Older versions had pretty poor performance on multi-gpu when not using nvlink, so it's possible this could be the issue. Please try upgrading to the latest (we released 6.0.2.0 yesterday) to see if that fixes your problem.
If it doesn't, then please add a full verbosity log file of a render so that we can better see what's going on.