Re: [Xen-users] vanilla linux, jumbo frames

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Mar 20, 2008 at 10:00:07AM -0700, Tom Brown wrote:
> On Tue, 18 Mar 2008, Tom Brown wrote:
> 
> >>
> >> Isn't these 100 mbps or 1000 mbps speeds funny numbers for today's CPU
> >> power? I mean, somewhere in the design, there's something wrong that
> >> forces
> >> us to make possibly too many context switches between DomU, Hypervisor 
> >> and
> >> Dom0. ???
> >>
> >> Emre
> >
> >what, something like the 1500 byte maximum transmission unit (MTU) from 
> >back in the days when 10 MILLION bits per second was so insanely fast we 
> >connected everything to the same cable!? (remember 1200 baud modems?) Yes, 
> >there might be some "design" decisions that don't work all that well today.
> >
> >AFAIK, XEN can't do oversize (jumbo) frames, that would be a big help for 
> >a lot of things (iSCSI, ATAoE, local network )... but even so, AFAIK it 
> >would only be a relatively small improvement (jumbo frames only going up 
> >to about 8k AFAIK).
> >
> >-Tom
> 
> My bad, As Pasi pointed out, it turns out that XEN has supported jumbo 
> frames since at least 3.0.4 ... of course, the AOE initiator support that 
> actually uses it seems to not be available until kernels 2.6.19 ... which 
> is too current for centos 5.1
> 
> so now I'm trying to boot 2.6.24.3 as a 32 PV guest on a 64 bit 
> hypervisor, and it's dieing at
> 
> Checking if this processor honours the WP bit even in supervisor mode... Ok.
> installing Xen timer for CPU 0
> ------------[ cut here ]------------
> kernel BUG at arch/x86/xen/time.c:122!
> invalid opcode: 0000 [#1] SMP
> 
> time.c 122 is the BUG line in the snippet below...
> 
> static void setup_runstate_info(int cpu)
> {
>         struct vcpu_register_runstate_memory_area area;
> 
>         area.addr.v = &per_cpu(runstate, cpu);
> 
>         if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
>                                cpu, &area))
>                 BUG();
> }
> 
> 
> 
> Is this 32 bit on 64 bit hypervisor supposed to work for vanilla linux?
> 

Xen (3.1) in CentOS 5.1 doesn't support 32-on-64. 

RHEL 5.2 / CentOS 5.2 will have 32-on-64 as a technology preview and it
should work.. 

-- Pasi

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users