Hi,

I was trying to set irq affinity by writing a value
to /proc/irq/<irq>/smp_affinity,
but smp_affinity value was not changed at all.
Ian suggested to take this to the devel list.
I'm working on Xen4.5, ARMv8.

Thanks,
Jintack

On Thu, Sep 3, 2015 at 11:34 AM, Ian Campbell <ian.campbell@citrix.com>
wrote:

> On Thu, 2015-09-03 at 10:59 -0400, Jintack Lim wrote:
> > 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.
> >
> > # cat /proc/irq/106/smp_affinity
> > 1
> >
> > # cat /proc/interrupts
> > ...
> > 106:      53849          0          0          0   xen-dyn-event
> > vif1.1-q0-tx
> > 107:          1          0          0          0   xen-dyn-event
> > vif1.1-q0-rx
> > 108:      61460          0          0          0   xen-dyn-event
> > vif1.1-q1-tx
> > 109:          1          0          0          0   xen-dyn-event
> > vif1.1-q1-rx
> > 110:      67118          0          0          0   xen-dyn-event
> > vif1.1-q2-tx
> > 111:          1          0          0          0   xen-dyn-event
> > vif1.1-q2-rx
> > 112:      58273          0          0          0   xen-dyn-event
> > vif1.1-q3-tx
> > 113:          1          0          0          0   xen-dyn-event
> > vif1.1-q3-rx
> > ...
> >
> > What would be the way to change smp_affinity?
>
> It should be via /proc/irq/<irq>/smp_affinity as you've tried, I asked
> Stefano and he things this was already implemented in 4.5 even. That it is
> not happening would be a bug, I think.
>
> I'd suggest you take this to the devel list as a bug.
>
> > and where is the affinity set initially for netback tx interrupts?
>
> Not, sure, I think it might just be generic IRQ code.
>
> Ian.
>
>