Re: [Xen-devel] [PATCH v6 02/23] xen: move NUMA_NO_NODE to public memory.h as XEN_NUMA_NO_NODE

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.03.15 at 04:42, <raistlin.df@xxxxxxxxx> wrote:
> On Mon, 2015-03-02 at 18:19 +0000, Andrew Cooper wrote:
>> In this case, a pnode of XEN_NO_NUMA_NODE seems like precisely the
>> correct value to report.
>> 
> Indeed. It tells Xen: <<hey Xen, toolstack here: we either don't care or
> could not come up with any sane vnode-to-pnode mapping, please figure
> that out yourself>>.
> 
> That makes the code, IMO, simpler at any level. In fact, at Xen level,
> there is a default way to deal with the situation (the striping)
> already. At the toolstack level, we can only care about trying to come
> up with some super-cool and super-good (for performance) configuration
> and just give up, if anything like what David and Andrew said occurs.

See my earlier reply - the tool stack at least giving hints to the
hypervisor in such a case would likely still be better (for the final
result) than leaving it entirely up to the hypervisor: "No node"
really means allocate from anywhere, whereas some specific
node passed in still allows the hypervisor to find second best fits
when having to fall back.

Jan


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