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Re: [Xen-devel] Maximum number of domains and NR_IRQS

  • To: "Carb, Brian A" <Brian.Carb@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: Keir Fraser <keir@xxxxxxxxxxxxx>
  • Date: Thu, 07 Dec 2006 15:50:41 +0000
  • Delivery-date: Thu, 07 Dec 2006 07:50:49 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AccaFYwFy8r1fHrHTUe4UDnJ0i4NHgAAeZuM
  • Thread-topic: [Xen-devel] Maximum number of domains and NR_IRQS

On 7/12/06 15:37, "Carb, Brian A" <Brian.Carb@xxxxxxxxxx> wrote:

We successfully start 118 DOMUs, but when we try to start the 119th, the system panics with the following messages:
  Kernel panic - not syncing: No available IRQ to bind to: increase NR_IRQS!
  (XEN) Domain 0 crashed: rebooting machine in 5 seconds.

The documentation in include/asm-x86_64/irq.h suggests that the value of NR_IRQS under x86_64 is limited to 256. In fact, when we rebuilt xen-unstable with NR_IRQS set to 768, the kernel panics on boot (see below).

It’s not Xen’s NR_IRQS you should increase; only Linux’s.

This out-of-IRQs condition shouldn’t crash the dom0 of course. I’ll look into that.

 -- Keir
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