[vfio-users] Memory allocation with numatune

[Alex Williamson]

On Sat, 28 Jan 2017 12:58:41 +0100
Thomas Lindroth <thomas.lindroth at gmail.com> wrote:

> On 01/27/2017 04:52 PM, Alex Williamson wrote:
> > vcpupin actually looks a little off though, just like on the host, the
> > VM is going to enumerate cores then threads  
> 
> Are you sure about that? Perhaps there is some numa trick I don't
> understand but it looks like the guest is a regular 6 cores
> with HT (<topology sockets='1' cores='6' threads='2'/>) and
> for me setups like that results in a layouts like this in the
> guest (qemu-2.8.0):
> 
> cat /proc/cpuinfo |grep "core id"
> core id         : 0
> core id         : 0
> core id         : 1
> core id         : 1
> core id         : 2
> core id         : 2
> 
> The ordering in the guest is threads then cores but for the
> host it's the other way around
> 
> cat /proc/cpuinfo |grep "core id"
> core id         : 0
> core id         : 1
> core id         : 2
> core id         : 3
> core id         : 0
> core id         : 1
> core id         : 2
> core id         : 3
> 
> Cores then threads. So to get a 1:1 match I have to use
> pinning like this which is similar to that numa setup.
> 
> <vcpupin vcpu='0' cpuset='1'/>
> <vcpupin vcpu='1' cpuset='5'/>
> <vcpupin vcpu='2' cpuset='2'/>
> <vcpupin vcpu='3' cpuset='6'/>
> <vcpupin vcpu='4' cpuset='3'/>
> <vcpupin vcpu='5' cpuset='7'/>
> <topology sockets='1' cores='3' threads='2'/>

Oh wow, maybe I'm completely off.  I hadn't noticed the core-id
ordering in the VM, but indeed on my system the guest shows:

core id		: 0
core id		: 0
core id		: 1
core id		: 1
core id		: 2
core id		: 2
core id		: 3
core id		: 3

Any physical system I've seen has the ordering you show above,
enumerating cores then threads.  Sorry Jan, maybe the way you had it
originally was optimal.  Thanks,

Alex