Re: [Xen-devel] [OSSTEST PATCH 1/2] TestSupport.pm: allow creating vNUMA enabled HVM guest configs

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Fri, 2015-10-02 at 12:32 +0100, Wei Liu wrote:
> On Fri, Oct 02, 2015 at 01:17:31AM +0200, Dario Faggioli wrote:

> > diff --git a/Osstest/TestSupport.pm b/Osstest/TestSupport.pm
> > index 2b67e32..bf8bd56 100644
> > --- a/Osstest/TestSupport.pm
> > +++ b/Osstest/TestSupport.pm
> > @@ -1709,6 +1709,34 @@ sub prepareguest_part_xencfg ($$$$$) {

> > +        # Let's put all vnodes on pnode 0, as we don't even know
> > (for now)
> > +        # whether or not the host has more NUMA nodes than that!
> > +        @vnuma_pnode = (0) x $vnuma_nodes;
> > +
> 
> The thing I worry about putting everything in node 0 is that if we
> somehow has hardware that has several nodes but each node has
> relative
> small amount of ram it would cause this test case to fail.
> 
ISWYM.

> In the current arrangement, HVM guest gets 5G of ram if OSSTest
> determines the host has enough (2x5G + slack) ram for it.  So vnuma
> test
> case will fail on a box with 4 nodes but has 16G of ram. Is such
> hardware configuration not very likely to exist?
> 
Well, 16GB is a rather small amount of RAM for a box with 4 nodes, IMO.

However, I think your point is valid... I think I can, in case
vnuma_nodes is provided, overrun $ram_mb with something more likely to
fit on one physical node?

Unfortunately, it's not something we can check precisely, because, in
Xen, there is (yet) no mechanism to know, in case we have XX free RAM
(apart from parsing the console output after issuing `xl debug-key u',
which is really really unpractical!), how many of it actually comes
from each NUMA ndoe... but I can apply a bit of guessing.

What do you think?

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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