Re: [RFC PATCH 2/2] xen: tmem: make tmem aware of NUMA affinity

[Bob Liu <bob.liu@oracle.com>]

On 03/20/2014 05:26 PM, Jan Beulich wrote:
>>>> On 19.03.14 at 18:12, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
>> Would you perhaps reconsider reviewing the code that Bob
>> posted and ignore the committing part of it until a later time
>> (when tmem has gotten throught the security audit).
> 
> The code looked reasonable, albeit I'm not certain it's to the
> point: Aren't certain types of pages sharable between domains?

Yes.

> For those, setting the affinity based on the domain for which
> the allocation gets done doesn't seem ideal. Plus the domain

The ideal situation for tmem is try to allocate pages from nodes in
domain's node_affinity, if there isn't enough memory on those nodes then
fall back to other online nodes.

Do you have any suggestion how to implement this?

> heap use of tmem was found to be broken anyway, and hence

Yes, but I think it's still better if tmem prefers nodes in
domain->node_affinity rather than all online nodes.

> extending the respective allocation interface seems odd from a
> second viewing angle too.
> 
> On the upside of things I would expect to find further uses for
> the extended domain page allocation interface. I'm wondering
> though whether we couldn't get away without adding yet
> another wrapper function: Considering that the passed in
> node mask is ignored if d != NULL, making the first argument
> a transparent union and adding _MEMF_nodemask to indicate
> that the passed in pointer is to a nodemask_t rather than a
> struct domain, we could stay with the current single interface.
> Inline type-safe accessors to both variants would then seem
> to be the way to go.
> 

Thank you for your review!

-- 
Regards,
-Bob