There's been a lot of rumors floating around internally at Yahoo that it's best to turn off some of your CPU cores when using Innodb, especially if you have a machine with > 4 cores. At this point there's no question in my mind that Innodb doesn't perform much better when you double your cores from 4 to 8, but I really wanted to know if 8 actually performed worse.
To test, I used a Dell 2950 with 6 drives and a simple mysqlslap test script. There's basically no I/O going on here, just a small table in memory being queried a lot. To be fair, I actually got this test from Venu. I used maxcpu=4 in my grub.conf to limit the cpus (I also tested with tasksel and it seemed to have the same effect as maxcpu).
