Using multiple CPUs

[Ira Holtzer]

Hi,

We have MySQL on multiple servers in production for a while now. Today while looking into an optimization problem we were having, we found that mysql is using only 1 of the 2 CPUs on the box. These are HP DL360 G7 with 2 X E5620 (or sometimes E5630) CPUs. cpuinfo is showing 16 processors, 2 X quad X 2 HW Threads/core = 16.

The OS is Centos 5.5 and our mysql versions are 5.5.8-11 depending on the box.

running atop we see below (hopefully) that only one cpu is utilized (seeing 8 "processors" working). Actually it's all the odd numbered processors. I am not 100% sure how linux is numbering them, but it seems to me they are all on the same CPU.
As far as I understood mysql should use all processors it has available, and there is no setting for CPU usage/affinity

CPU | sys 17% | user 194% | irq 6% | | | idle 1382% | wait 0% | | | steal 0% | guest 0% |
cpu | sys 2% | user 27% | irq 1% | | | idle 69% | cpu009 w 0% | | | steal 0% | guest 0% |
cpu | sys 2% | user 24% | irq 1% | | | idle 72% | cpu001 w 0% | | | steal 0% | guest 0% |
cpu | sys 2% | user 24% | irq 1% | | | idle 73% | cpu013 w 0% | | | steal 0% | guest 0% |
cpu | sys 2% | user 24% | irq 1% | | | idle 73% | cpu005 w 0% | | | steal 0% | guest 0% |
cpu | sys 2% | user 23% | irq 1% | | | idle 75% | cpu011 w 0% | | | steal 0% | guest 0% |
cpu | sys 2% | user 21% | irq 1% | | | idle 77% | cpu015 w 0% | | | steal 0% | guest 0% |
cpu | sys 2% | user 20% | irq 1% | | | idle 78% | cpu003 w 0% | | | steal 0% | guest 0% |
cpu | sys 2% | user 17% | irq 1% | | | idle 81% | cpu007 w 0% | | | steal 0% | guest 0% |
cpu | sys 0% | user 3% | irq 0% | | | idle 96% | cpu004 w 0% | | | steal 0% | guest 0% |
cpu | sys 0% | user 2% | irq 0% | | | idle 98% | cpu000 w 0% | | | steal 0% | guest 0% |
cpu | sys 0% | user 2% | irq 0% | | | idle 98% | cpu012 w 0% | | | steal 0% | guest 0% |
cpu | sys 0% | user 2% | irq 0% | | | idle 98% | cpu014 w 0% | | | steal 0% | guest 0% |
cpu | sys 0% | user 2% | irq 0% | | | idle 98% | cpu008 w 0% | | | steal 0% | guest 0% |
cpu | sys 0% | user 1% | irq 0% | | | idle 98% | cpu010 w 0% | | | steal 0% | guest 0% |
cpu | sys 0% | user 1% | irq 0% | | | idle 99% | cpu006 w 0% | | | steal 0% | guest 0% |
cpu | sys 0% | user 1% | irq 0% | | | idle 99% | cpu002 w 0% | | | steal 0% | guest 0% |

Did I get it right?
Can I tell mysql to use the other cpu? is there a point?