Re: A bunch of questions about getting a working NetBSD/xen system

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Tue, Feb 02, 2010 at 06:16:11PM -0500, Louis Guillaume wrote:
>
> 1. What I have:
>
>      o Dual 3Ghz 64-bit Xeons.
>      o 4G Ram.
>      o Tyan S5360 Mb.
>
>    From looking at the CPU specs it would appear that they have the
>    Intel VT technology needed for HVM support.

If it's not dual-core it's for sure not VT. Looking at the
S5360, it looks like this motherboard is too old to support any
Intel CPU with VT.

>    So - first question: Will it work? Or am I stuck with non-HVM and
>    only modified kernels?

Without CPU support HVM will not work.

> 2. I've been running a -current kernel as it's been suggested that
>    only -current kernels will work. But then I've seen somewhere
>    that netbsd-5 should work fine.
>
>    Can I use netbsd-5 instead of -current for DOM0/PAE yet?

netbsd-5 support dom0 PAE now.

>
>
> 3. I have DOM0 working with -current. But it seems awfully slow! Disk
>    I/O and also net I/O seem to be much slower than normal. Is there
>    anything that needs to be done to have reasonable performance in
>    DOM0. Will the DOMU's be able to perform well despite the slowness
>    in DOM0?

What do you use to measure this ? Maybe it's because the dom0 doesn't
have enough RAM ?
On my systems, I can't see a difference in I/O performances between
native and Xen dom0.

>
>
> 4. Is it "bad" practice to use the DOM0 for anything other than
>    serving the guest oses? For example - bad idea to build.sh the
>    system in DOM0 or compile pkgsrc packages?

I would avoid it, especially for packages. It's so easy to setup
a guest for this purpose :)

>
>
> 5. If I'm able to get an HVM setup going, will NetBSD run unmodified
>    as a guest?

Yes (maybe you'll have to disable re(4)).

>
>
> 6. What's the deal with SMP on xen? I see the following in dmesg:
>
>      cpu0 at mainbus0 apid 0: (boot processor)
>      cpu1 at mainbus0 apid 6: (application processor)
>      cpu2 at mainbus0 apid 1: (application processor)
>      cpu3 at mainbus0 apid 7: (application processor)
>
>    and things like "top" only show one processor active. Last time I
>    think I saw this separation of "boot" vs. "application" processor
>    was in netbsd-2 or -3, I think.
>
>    What should I expect to see here in DOM0?
>
>    Can I run SMP guests?

NetBSD doesn't run SMP on Xen at this time. But the hypervisor itself can
schedule different guests on different CPUs, and if you run a SMP-aware
guest, it'll be able to use more than one CPU.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--