Thanks Julien. On Thu, Sep 3, 2015 at 2:21 PM, Julien Grall <julien.gr...@citrix.com> wrote:
> On 03/09/15 17:06, Jintack Lim wrote: > > Hi, > > Hi Jintack, > > > On Thu, Sep 3, 2015 at 11:34 AM, Ian Campbell <ian.campb...@citrix.com > > <mailto:ian.campb...@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? > > All those interrupts are in-fine event channels. This is a bug in Linux > which I sent a fix a month ago and it's queued in xentip for Linux 4.3 [1] > > The event channel rebinding was not working because we don't have vector > callback on ARM and therefore the driver was only allowing event channel > to be routed on VCPU0. > > After applying this patch, I was able to set smp_affinity. In addition, the default value of smp_affinity for netback tx interrupts on Dom0 becomes "f" (I have four vcpus on Dom0). What I meant by 'netback tx interrupts' is vif1.1-q<num>-tx This is slightly different from x86, because netback tx interrupts are pinned to separate vcpus on x86. I'm not sure this question is appropriate for devel-list, but why the policy to set smp_affinity for netback tx interrupts are different on ARM and x86? > commit 4a5b69464e51f4a8dd432e8c2a1468630df1a53c > Author: Julien Grall <julien.gr...@citrix.com> > Date: Tue Jul 28 10:10:42 2015 +0100 > > xen/events: Support event channel rebind on ARM > Currently, the event channel rebind code is gated with the presence of > the vector callback. > > The virtual interrupt controller on ARM has the concept of per-CPU > interrupt (PPI) which allow us to support per-VCPU event > channel.Therefore there is no need of vector callback for ARM. > > Xen is already using a free PPI to notify the guest VCPU of an event. > Furthermore, the xen code initialization in Linux (see > arch/arm/xen/enlighten.c) is requesting correctly a per-CPU IRQ. > > Introduce new helper xen_support_evtchn_rebind to allow architecture > decide whether rebind an event is support or not. It will always return > true on ARM and keep the same behavior on x86. > > This is also allow us to drop the usage of xen_have_vector_callback > entirely in the ARM code. > > Signed-off-by: Julien Grall <julien.gr...@citrix.com> > Signed-off-by: David Vrabel <david.vra...@citrix.com> > > Regards, > > [1] https://lkml.org/lkml/2015/7/28/205 > > -- > Julien Grall > >
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