I'm getting about 20-25% cpu usage on gentoo (htop shows the main process accounts for all of this, but there are about 10 other cgminer entries) with an amd 8350 and two 7950s. I have another box with one 5770 and one 7950 and it showed similar behavior (about 13% cpu usage). If I disable the 7950 then the usage goes down to 3-4%. I am using -I 5,8 -w 256 -v 1 and I have tried all of the kernels. I have also tried cgminer 2.10.4 and 2.11.2. I have another couple boxes with 5830s and 5770s that have less than 2% cpu usage. Any thoughts as to why the 7950 boxes have higher cpu usage?
From what I can gather, mixing 7xxx series cards with 5xxx or 6xxx series cards causes issues, as they prefer to have different driver/sdk setups. There is plenty of info elsewhere on the forums about it, that's how I found out. I keep all my 7xxx series separate in their own rig. Here's one link that might help you:
https://bitcointalk.org/index.php?topic=77950.0Or, do a search for "7970 settings". Hope it helps a bit.......
Peace.