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Fwd: [Xen-devel] Question Also regarding interrupt balancing

  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: harish <mvharish@xxxxxxxxx>
  • Date: Thu, 29 Jun 2006 12:13:41 -0700
  • Delivery-date: Thu, 29 Jun 2006 12:14:10 -0700
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  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

FWD...forgot to cc the group.

I was not clear in my last email and so trying to rephrase the question with an example:

peth0   --> pcpu2 [mapped this using the proc interface]
domU1 --> pcpu3

Noticed that the physical interrupts were getting routed to pcpu2 and so the mapping worked. However noticed that there were significant number of virtual interrupts corresponding to vif1.0 [used by domU1]. The interrupts were serviced by pcpu0. It is this interrupts that I was talking about in my earlier question.

I thought interrupts of type "Dynamic-irq" in general cannot be set using proc interface. Please correct me if I am wrong but from your response below it looks like we can. Anyways I tried setting it using the /proc interface for the virtual interrupts corresponding to vif1.0 and it did not work.

How are the virtual interrupts mapped? Yet to see a test where the virtual interrupts run on a pcpu other than pcpu0 and so wondering if there is a explicit mapping in the code.

Hope my question makes sense now?


On 6/29/06, Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> wrote:

On 29 Jun 2006, at 16:51, harish wrote:

>  And ran a quick netperf test. Noticed that the cpu utilization was
> around ~50% on pcpu0 although my interrupts were being pinned to pcpu2
> and domU on pcpu3. That is when I noticed that vif#id.0 has a dynamic
> irq which is serviced by pcpu0. Does this irq always run on pcpu0?
> Considering that it is dynamic, I understand that we cannot change the
> affinity and so am wondering if there some other configuration related
> to it.

Again, we don't load balance in the kernel, but you could change its
affinity to some other single CPU via the proc interface.

  -- Keir

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