[Xen-users] Changing netback tx interrupts affinity on Dom0

[Jintack Lim <jintack@xxxxxxxxxxxxxxx>]

Hi,

While I was running Apache server,

I found that one of Dom0 vcpu is running 100% to handle irqs,

and those irqs are set to be processed only on that specific vcpu.

Referring to this document,

http://wiki.xen.org/wiki/Network_Throughput_and_Performance_Guide

I tried to change smp_affinity by writing a value to /proc/irq/<irq-no>/smp_affinity,

however the smp_affinity value was not changed.

I'm working on Xen 4.5 on ARMv8,

and the irq is netback tx interrupt.

#Âcat /proc/irq/106/smp_affinity

1

# cat /proc/interrupts

...

106:   Â53849     Â0     Â0     Â0  xen-dyn-event   vif1.1-q0-tx

107:     Â1     Â0     Â0     Â0  xen-dyn-event   vif1.1-q0-rx

108:   Â61460     Â0     Â0     Â0  xen-dyn-event   vif1.1-q1-tx

109:     Â1     Â0     Â0     Â0  xen-dyn-event   vif1.1-q1-rx

110:   Â67118     Â0     Â0     Â0  xen-dyn-event   vif1.1-q2-tx

111:     Â1     Â0     Â0     Â0  xen-dyn-event   vif1.1-q2-rx

112:   Â58273     Â0     Â0     Â0  xen-dyn-event   vif1.1-q3-tx

113:     Â1     Â0     Â0     Â0  xen-dyn-event   vif1.1-q3-rx

...

What would be the way to change smp_affinity?

and where is the affinity set initially for netback tx interrupts?

Thanks,

Jintack

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