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Re: Domain 0 kernel, DAC960 and SMP



Manuel Bouyer wrote:

On Wed, May 24, 2006 at 05:38:54PM +0200, Hubert Feyrer wrote:
On Wed, 24 May 2006, Tillman Hodgson wrote:
Is building a custom Xen kernel for this as easy as adding in the
GENERIC.MP changes and something like this for device support?:
Read http://www.netbsd.org/Ports/xen/howto.html#pci-devices

I'd add that using a recent XEN0 kernel from the netbsd-3 branch should
have the drivers for this hardware. This has been added some weeks ago.

As for SMP, I'm not sure if Xen2 supports that.
Support for Xen3 domU and I think dom0 is in -current. (there may be some code on the netbsd-3 branch, but I forgot)

With Xen2, multiple CPUs can't be used by a single domain, but if you
have multiple domains running, the hypervisor will schedule them on different
CPUs.
The assignement is done on domain startup, you can't move a domain from one
CPU to another once started.

With Xen3, it's theorically possible to have one domain use multiple CPUs
but NetBSD doesn't support that yet. I suspect the hypervisor can move
domains from one cpu to another dynamically but I didn't try this.

Xen 3 can *theorically* change CPU<->VCPU assignement while running, but the actual schedulers don't implement this. A new one is in test though, available in the lastest version of Xen (unstable ones, need to checkout and build sources). Use "sched=credit" on the command line. Note that i haven't tested it nor seen any feedback on this, it's fairly new... As a side note, i'd like to add that the current interrupt model in Xen is pretty weak in some cases. As all interrupts are routed to VCPU0, a machine with high interrupt load (like a router or a fileserver) will have CPU0 at about 100% load all the time while all others will remain idle.




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