Re: PV-vNUMA issue: topology is misinterpreted by the guest

[Dario Faggioli <dario.faggioli@citrix.com>]

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On Tue, 2015-07-28 at 11:05 +0100, Wei Liu wrote:
> On Fri, Jul 24, 2015 at 06:05:59PM +0200, Dario Faggioli wrote:

> > BTW, I've also been grepping, and I'm not seeing XENMEM_get_vnumainfo
> > being called anywhere either... Well, no wonder, we're seeing vNUMA
> > setup issues! If I did check for this before, I wouldn't even have
> > tested PV-vNUMA in the first place!! :-O
> > 
> > I actually wonder how _some_ of the vNUMA info get through!?!? :-O
> > 
> 
> Maybe you're using a custom built kernel with my PV vNUMA patch in?
> 
Yep, that must be the case... I only recalled about that after sending
this email (no, I don't update Dom0/guest kernel for my testbox really
often! :-/)

> I sent that to you once because you wanted to test that.
> 
And I confirmed it. Booting the guest with Debian's stick 4.0.0, I get
this from Xen:

(XEN) Memory location of each domain:
(XEN) Domain 0 (total: 129914):
(XEN)     Node 0: 56111
(XEN)     Node 1: 73803
(XEN) Domain 2 (total: 262144):
(XEN)     Node 0: 131072
(XEN)     Node 1: 131072
(XEN)      2 vnodes, 4 vcpus, guest physical layout:
(XEN)          0: pnode   0, vcpus 0-1 
(XEN)            0000000000000000 - 0000000020000000
(XEN)          1: pnode   1, vcpus 2-3
(XEN)            0000000020000000 - 0000000040000000


But the (PV) guest does not actually know anything about vNUMA:

root@test:~# numactl --hardware
available: 1 nodes (0)
node 0 cpus: 0 1 2 3
node 0 size: 993 MB
node 0 free: 918 MB
node distances:
node   0 
  0:  10 

Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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