Re: [Xen-devel] domain creation vs querying free memory (xend and xl)

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-10-04 at 11:06 +0100, Tim Deegan wrote:
> but my question was really: what should xl do, in the presence of
> ballooning, sharing, paging and tmem, to
>  - decide whether a VM can be started at all;
>  - control those four systems to shuffle memory around; and
>  - resolve races sensibly to avoid small VMs deferring large ones.
> (AIUI, xl already has some logic to handle the case of balloon-to-fit.)
> 
> The second of those three is the interesting one.  It seems to me that
> if the tools can't force all other actors to give up memory (and not
> immediately take it back) then they can't guarantee to be able to start
> a new VM, even with the new reservation hypercalls.

There was a bit of discussion in the spring about this sort of thing
(well, three of the four), which seems to have fallen a bit by the
wayside^W^W^W^W^W^Wbeen deferred until 4.3 (ahem) e.g.
http://lists.xen.org/archives/html/xen-devel/2012-03/msg01181.html

I'm sure there was earlier discussion which led to that, but I can't
seem to see it in the archives right now, perhaps I'm not looking for
the right Subject.

Olaf might have been intending to look into this (I can't quite remember
where we left it)

Ian.



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