Xen project Mailing List

I haven't been using NUMA things in recent years, so my intel may not be correct.

Actually, I think it's quite difficult to retrieve such info through a command, as Xen only provide some numa placement & scheduling (load-balancing) support (and vNuma feature, maybe it's still experimental but last time I tried it, it was functional). From my understanding, probing memory allocation would be difficult as such things are dynamic, or maybe it is just not worthy of the effort.

Reasons are:

First numa placement tries to allocate as much as (in most cases Xen will find a node which can fit the VM's memory requirement) memory to local nodes (let's say 4 vcpus are pinned to node 0 then it's a local node), but it seems xen doesn't care how much memory has been allocated to a certain VM under such situations (as it tries to allocate as much as possible on one node, assuming if a VM's VCPUs are spread among several nodes, rare but possible). As having 800MB on node 0 is pretty much the same as 900MB on node 0 if your VM requires 1GB, both will have a similar performance impact on your VM.

Second, a VM can be migrated to other nodes due to load balancing, which may makes it harder to count how much memory has been allocated for a certain VM on each node.

If you can't find useful info in Xenstore, then perhaps such feature you required is not yet available.

However, if you just want to know the memory usage on each node, perhaps you could try numactl and get some outputs? Or try libvirt? I remember numastat can give some intel about memory usage on each node.

Or, try combine NUMA support with vNUMA, perhaps you can get such info inside a VM.

Best,

Kun

On Mon, Jan 9, 2017 at 5:43 PM Eike Waldt <waldt@xxxxxxxxxxxxx> wrote:

On 01/04/2017 03:15 PM, Eike Waldt wrote:
> Hi Xen users,
>
> on [0] under #Querying Memory Distribution it says:
>
> "Up to Xen 4.4, there is no easy way to figure out how much memory from
> each domain has been allocated on each NUMA node in the host."
>
> Is there a way in xen 4.7 ?
anybody?
>
> [0] https://wiki.xen.org/wiki/Xen_on_NUMA_Machines
>
>
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxx
> https://lists.xen.org/xen-users
>

--
Eike Waldt
Linux Consultant
Tel.: +49-175-7241189
Mail: waldt@xxxxxxxxxxxxx

B1 Systems GmbH
Osterfeldstraße 7 / 85088 Vohburg / http://www.b1-systems.de
GF: Ralph Dehner / Unternehmenssitz: Vohburg / AG: Ingolstadt,HRB 3537

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxx
https://lists.xen.org/xen-users

Re: [Xen-users] query memory allocation per NUMA node