[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

  • To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
  • From: harish <mvharish@xxxxxxxxx>
  • Date: Thu, 29 Jun 2006 08:51:06 -0700
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Thu, 29 Jun 2006 08:51:28 -0700
  • Domainkey-signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:references; b=eAND/wXuSUncnoVLCkG5KN0Frypdkf0jiRcz1l8wbDXkYYhYNzF13VRsg85G6zwZJAPHDMozRCKvwTp3PQAeZE24ac77AIL+l/gGtwJjii09+TgK/QKf7TtjTbIPjAyG7DySjzR8wY7NLhxleu+OTbCN3dyB7HzwZSL23oELvvg=
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

Hi Keir,
I had tried the following experiment on a 4-way machine:

1) Pin the physical interrupts for the physical nic to pcpu1
2) Pin the domU to pcpu3

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.

Any suggestions/help would be great.


On 6/13/06, Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> wrote:

On 13 Jun 2006, at 00:42, harish wrote:

> echo 2 > /proc/irq/20/smp_affinity [...works..]
> echo 4 > /proc/irq/20/smp_affinity [...works..]
> echo 8 > /proc/irq/20/smp_affinity [...works..]
> But, a cumulative does not work...meaning...
> echo 3>
> echo 5>
> echo f> etc.... do not work.
> Is that a bug or is it by design?

You should find it locks onto the first CPU in the mask that you
specify. As I said, the kernel does not load-balance IRQs so it
currently does not make sense to specify multi-cpu cpumasks. So this is
by design, for now.

  -- Keir

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.