On Thu, Sep 3, 2015 at 12:06 PM, Jintack Lim <jintack@cs.columbia.edu> wrote:
<= blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px= #ccc solid;padding-left:1ex">

Hi,

I was= trying to set irq affinity by writing a value to=C2=A0/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 wor= king on Xen4.5, ARMv8.

I checke= d that setting smp_affinity works on Xen4.5, x86.

So, probably th= is is an ARM specific issue.

=C2=A0

Thanks,
Jintack
=

On Thu, Sep 3, 2015 at 11:34 AM, Ian Campbell <<= a href=3D"mailto:ian.campbell@citrix.com" target=3D"_blank" onclick=3D"wind= ow.open('https://mail.google.com/mail/?view=3Dcm&tf=3D1&to=3Dia= n.campbell@citrix.com&cc=3D&bcc=3D&su=3D&body=3D','= _blank');return false;">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/Netwo= rk_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:=C2=A0 =C2=A0 =C2=A0 53849=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2=A0= =C2=A0xen-dyn-event
> vif1.1-q0-tx
> 107:=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 1=C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 0=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 0=C2=A0 =C2=A0xen-dyn-event
> vif1.1-q0-rx
> 108:=C2=A0 =C2=A0 =C2=A0 61460=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2=A0= =C2=A0xen-dyn-event
> vif1.1-q1-tx
> 109:=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 1=C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 0=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 0=C2=A0 =C2=A0xen-dyn-event
> vif1.1-q1-rx
> 110:=C2=A0 =C2=A0 =C2=A0 67118=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2=A0= =C2=A0xen-dyn-event
> vif1.1-q2-tx
> 111:=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 1=C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 0=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 0=C2=A0 =C2=A0xen-dyn-event
> vif1.1-q2-rx
> 112:=C2=A0 =C2=A0 =C2=A0 58273=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2=A0= =C2=A0xen-dyn-event
> vif1.1-q3-tx
> 113:=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 1=C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 0=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 0=C2=A0 =C2=A0xen-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<= br> 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.

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