CPU interrupts affinity on IMX6Q

jignesh1 — Mon, 06 Aug 2018 06:34:45 GMT

Hi All,

Processor : IMX6Q (MCIMX6Q6AVT10AD)

Linux Kernel : 4.9.11

Kernel reference : wandboard_imx_4.9.11_1.0.0_ga

We are making IMX6Q based product. In our product we use USB modems for data transmission.
In IMX6Q there are 4 Cortex-A9 cores. What we observe is mostly all the interrupts are coming on CPU0 core.
Theoretically it should equally distribute to all the cores.
I search and read about interrupt affinity. LXR / The Linux Cross Reference and tried change affinity mask (smp_affinity) for the process which is responsible for data transmission.
But what I observe is event though I changed mask (smp_affinity) it not distributed to all the cores it always fall on any CPU at a time.
Default affinity mask (smp_affinity) value is "0xF" which is correct to distribute interrupts on all the four cores but behavior is different.
Question is why this mask has no effect? Am I missing anything?
Second observation is not all the process are have smp_affinity mask. May I know what is reason behind it?

Any suggestion/direction/comment would be appreciated.

Thanks,

Jignesh

Re: CPU interrupts affinity on IMX6Q

jignesh1 — Mon, 27 Aug 2018 05:10:03 GMT

Any update on above post. I really stuck here.