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

[Gareth Bult <gareth@xxxxxxxxxxxxx>]

fyi; I'm using the latest AOE on 2.6.21 RH kernels .. Jumbo's don't work for me 
(!)

(and I spent many days trying ...)

----- Original Message -----
From: "Tom Brown" <xensource.com@xxxxxxxxxxxxxxxxxxx>
To: "xen-users" <xen-users@xxxxxxxxxxxxxxxxxxx>
Sent: Thursday, March 20, 2008 5:00:07 PM GMT +00:00 GMT Britain, Ireland, 
Portugal
Subject: [Xen-users] vanilla linux, jumbo frames

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?

-Tom

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