multi-core box: meaning of ps aux output?

MMaddoxx · 01-13-2012, 07:03 AM

Hi

Question arose because my job on a shared box was running real slow.

from running

Code:

$ less /proc/cpuinfo

the box has 6x Intel(R) Xeon(R) CPU X5650 @ 2.67GHz

When I use

Quote:

$ps -eo pid,user,%cpu,%mem,args --sort %cpu

to see the processes using most %cpu, I get (some details removed to protect the innocent)

Quote:

PID USER %CPU %MEM
1349 myID 10.7 7.1 sort -k 1,1 -S 8G -T.
1353 myID 10.8 7.1 sort -k 1,1 -S 8G -T.
1375 myID 11.7 0.0 awk {my awk task
917 xxID 99.7 0.0 /path/to/exe

First observation: the %cpu figures add up to >100%.
Is this because the PIDs are running on separate chips? (my two sorts are threads running from perl ... are they also on separate chips?)

If each of these PID is on a separate chip, can my own job's slow running be caused by that cpu-hogging (99.7%) job I first suspected?

I will wait until that job finishes and try mine again, but I'm kindof curious as to how the system works.

m

AlucardZero · 01-13-2012, 08:32 AM

You get 100% per core. So with 6 cores you should see a max of 600% (this is not an exact science, so you could potentially see slightly over).