Re: [Xen-devel] Spurious "NUMA placement failed, performance might be affected" message on ARM

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On lun, 2014-04-28 at 13:15 +0100, Andrew Cooper wrote:
> On 28/04/14 12:30, Ian Campbell wrote:
> > On Mon, 2014-04-28 at 11:01 +0100, Ian Campbell wrote:
> > [...]
> >> total_memory           : 8184
> >> free_memory            : 6933
> > [...]
> >> node:    memsize    memfree    distances
> >>    0:      4088       3861      20
> > I think we are missing some RAM here...
> >
> > and I have now noticed that I only see this for guests which have more
> > RAM than this memfree value (+/- some slop). The guests succeed because
> > there is actually RAM available.
> >
> > I think this is enough for me to now track down the cause on the
> > hypervisor side. Thanks for your input.
> >
> > Ian.
> 
> Do be aware that the memsize value is "number of pages on this node"
> which includes IO mappings of non-ram regions, and as a result memfree
> is mostly fictitious.
> 
> I raised this as a concern with the hwloc code, but without any
> subsequent discussion.
> 
There has been another discussion about discrepancies in total and free
memory reporting. ISTR, it was noticed at the time when I added the
support for some of these NUMA stuff in libvirt.

I don't have it handy right now... I'll see if I can fetch it back,
merge it with your observations in the hwloc thread and (re)start a
discussion about this.

Regards,
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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