# SMP Affinity Changing?

#### JohnGraham

##### Newbie level 2
I'm working with the SMP affinity on an i.MX8 system (on a SolidRun HummingBoard Plus) and there are a couple of things that confuse me, but mostly that one of the affinities keeps changing.

It's for a timer interrupt, e.g.:

Code:
root@sr-imx8:~# cat /proc/irq/6/smp_affinity
4
root@sr-imx8:~# cat /proc/irq/6/smp_affinity
2
root@sr-imx8:~# cat /proc/irq/6/smp_affinity
2
root@sr-imx8:~# cat /proc/irq/6/smp_affinity
1
Anyone got any insight into this? I can't find anything on the web that explains any more about affinity than the basics.

It's a timer interrupt, if that makes any difference:

Code:
root@sr-imx8:~# grep -w 6: /proc/interrupts
6:      12833      12095      10157          1  GPC-PSCI  47 Edge      iMX system counter timer

#### bigendian

##### Newbie level 3
did you tried to force the affinity to a specific cpu ?

Maybe, being imx8 a big.LITTLE stuff, the affinity is just moved depending on active cores.

There are a lot of interrupt/affinity tutorial around but just basics. Looks like only thing to do to clarify more is entering the sources.