I'd like to change IRQ SMP affinity for reasons, outlined in this question: CPU0 is swamped with eth1 interrupts

But I can't — I see `Input/output error`

when I try to write to `/proc/irq/*/smp_affinity`

.

Please point me to the HOWTO on the matter. (A formal reference on `/proc/irq/*/`

would be cool as well.)

Gory details:

Note that this is a VM (PV domU) inside an Ubuntu-based Xen XCP host.

$ uname -a Linux MYHOST 2.6.38-15-virtual #59-Ubuntu SMP Fri Apr 27 16:40:18 UTC 2012 i686 i686 i386 GNU/Linux $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 11.04 Release: 11.04 Codename: natty $ sudo cat /proc/irq/*/smp_affinity 01 01 01 01 01 80 80 80 80 80 80 40 40 40 40 40 40 20 20 20 20 20 20 10 10 10 10 10 10 08 08 08 08 08 08 04 04 04 04 04 04 02 02 02 02 02 02 01 01 01 01 01 01

**Update.** The error details:

$ N=$(grep -c processor /proc/cpuinfo) $ echo $N 8 $ printf %x $((2**N-1)) ff $ printf %x $((2**N-1)) | sudo tee /proc/irq/*/smp_affinity fftee: /proc/irq/288/smp_affinity: Input/output error tee: /proc/irq/289/smp_affinity: Input/output error tee: /proc/irq/290/smp_affinity: Input/output error tee: /proc/irq/291/smp_affinity: Input/output error tee: /proc/irq/292/smp_affinity: Input/output error tee: /proc/irq/293/smp_affinity: Input/output error tee: /proc/irq/294/smp_affinity: Input/output error tee: /proc/irq/295/smp_affinity: Input/output error tee: /proc/irq/296/smp_affinity: Input/output error tee: /proc/irq/297/smp_affinity: Input/output error tee: /proc/irq/298/smp_affinity: Input/output error tee: /proc/irq/299/smp_affinity: Input/output error tee: /proc/irq/300/smp_affinity: Input/output error tee: /proc/irq/301/smp_affinity: Input/output error tee: /proc/irq/302/smp_affinity: Input/output error tee: /proc/irq/303/smp_affinity: Input/output error tee: /proc/irq/304/smp_affinity: Input/output error tee: /proc/irq/305/smp_affinity: Input/output error tee: /proc/irq/306/smp_affinity: Input/output error tee: /proc/irq/307/smp_affinity: Input/output error tee: /proc/irq/308/smp_affinity: Input/output error tee: /proc/irq/309/smp_affinity: Input/output error tee: /proc/irq/310/smp_affinity: Input/output error tee: /proc/irq/311/smp_affinity: Input/output error tee: /proc/irq/312/smp_affinity: Input/output error tee: /proc/irq/313/smp_affinity: Input/output error tee: /proc/irq/314/smp_affinity: Input/output error tee: /proc/irq/315/smp_affinity: Input/output error tee: /proc/irq/316/smp_affinity: Input/output error tee: /proc/irq/317/smp_affinity: Input/output error tee: /proc/irq/318/smp_affinity: Input/output error tee: /proc/irq/319/smp_affinity: Input/output error tee: /proc/irq/320/smp_affinity: Input/output error tee: /proc/irq/321/smp_affinity: Input/output error tee: /proc/irq/322/smp_affinity: Input/output error tee: /proc/irq/323/smp_affinity: Input/output error tee: /proc/irq/324/smp_affinity: Input/output error tee: /proc/irq/325/smp_affinity: Input/output error tee: /proc/irq/326/smp_affinity: Input/output error tee: /proc/irq/327/smp_affinity: Input/output error tee: /proc/irq/328/smp_affinity: Input/output error tee: /proc/irq/329/smp_affinity: Input/output error tee: /proc/irq/330/smp_affinity: Input/output error tee: /proc/irq/331/smp_affinity: Input/output error tee: /proc/irq/332/smp_affinity: Input/output error tee: /proc/irq/333/smp_affinity: Input/output error tee: /proc/irq/334/smp_affinity: Input/output error tee: /proc/irq/335/smp_affinity: Input/output error

**Update.** `irqbalance`

is running:

$ sudo service irqbalance status irqbalance start/running, process 560

`irqbalance`

is running. Maybe I'm just doing it wrong? – Alexander Gladysh Nov 9 '12 at 5:57