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

Re: [Xen-devel] Vcpu allocation for a newly created domU

  • To: Sandesh <sandesh.ahiremath@xxxxxxxxx>
  • From: "Grzegorz Miłoś" <gm281@xxxxxxxxx>
  • Date: Wed, 18 Jun 2008 12:13:53 +0100
  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Wed, 18 Jun 2008 04:14:15 -0700
  • Domainkey-signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references:x-google-sender-auth; b=jUWIP1ZZ7PjbIBQmuw37nqlDCtbWAEj+HGOAWfuPB3b4oMM0KQl4LoilkTBTaUZxyo IhmIRxIPwB9TGkUBsE7jlNXaPz6KfTHQAuqh+4uccqY73P4jLCAsrpPNB8xQkXTepUBV zpQ0+6lYNknnOOIaEMWDtnwkpK0YD4jw4hxGU=
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

> Hi all,
>  I am having confusion regarding the way a newly created domain is
> allocated vcpu.
>  Initially during dom0 creation alloc_vcpu is called to create vcpu
> structs for all the available cpu's and assigned to dom0. But its not
> the case for domU creation.
> 1. So how will dom0 relinquish/share vcpu to/with a newly created domU.
> Does this happen as part of the shared_info page mapping??

vcpus are created for each new domain, they are not shared with Dom0.

> 2. Till the end of DOMCTL_createdomain hypercall d->vcpu is null but by
> the start of xc_linux_bulid_internal function d->vcpu is pointing to
> some vcpu. How is this??

vcpus are created as a part of DOMCTL_max_vcpus. This hypercall is
issued by the tools in Dom0, specifically by: _constructDomain() in
python/xen/xend/XendDomainInfo.py. Look for the following line:
xc.domain_max_vcpus(self.domid, int(self.info['VCPUs_max']))

> 3. As part of the domU config file we can constraint the domU to a
> specific CPU. How is this achieved unless there is an explict way of
> assigning vcpu associated with that cpu number.

This is done by the following call chain:
DOMCTL_setvcpuaffinity ->
vcpu_set_affinity ->

Hope this helps.


Xen-devel mailing list



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