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[Xen-users] Dom0 scheduling on SMP systems

  • To: xen-users <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: "Amitayu Das" <amitayudas@xxxxxxxxx>
  • Date: Fri, 10 Mar 2006 12:20:13 -0500
  • Delivery-date: Fri, 10 Mar 2006 17:21:15 +0000
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  • List-id: Xen user discussion <xen-users.lists.xensource.com>


I've got a HT-enabled dual-preocessor Xeon machine, on which I'm running xen-3.0-testing. I've specified entries like the following in the configuration scripts for DomU's to prevent them running on CPU 0:

cpus = "1-4, ^0"

My question is

1. Does this type of specificaiton mean Dom0 would *always* be running on CPU0? Please note that this question is different from "if Dom0 will *only* run on CPU 0?" What I want to know is can be described with an example:

Say, any of the DomU's (running on CPUs other than 0) wants to do some I/O for which he needs help from Dom0. Now, is it the case that whenever any such situation is created, Dom0 will always be scheduled on CPU 0 to work for a DomU? OR, is it the case that whenever Dom0 is *scheduled* on CPU 0 , then only he services the requests from DomU's. The later would mean that Dom0 is *not* always scheduled on CPU 0. Please note that I'm not sure if Dom0 running on other CPUs (if at all) can provide services to DomU's or not (which can be prevented by setting "dom0-cpus" entry to 1 along with specification mentioned above, I presume).

2. I'd also like to know exactly how can I make Dom0 *only run* on CPU 0 while let DomUs running on other CPUs? Dom0 should be scheduled on *CPU 0* and not anywhere else?

Can anybody clarify the doubts?

Thanks in advance,
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