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[Xen-devel] dom0/pvh: Follow up discussion from xen-devel - Low hanging fruit

On Wed, Oct 31, 2018 at 05:07 PM +0200, Roger Pau Monné wrote:

> On Wed, Oct 31, 2018 at 04:38:08PM +0200, Alexandru Vasile wrote:
> > Hello,
> >
> >
> I am writing as a follow up from our discussion on the xen-devel mailing
> list [0].
> > You mentioned some ‘low-hanging fruit, both in Xen and the Linux kernel’ and
> if I am ever interested to talk about sharing the workload.
> > Could you share more details about this?

> - Xen: make sure PVH Dom0 works without the dom0_mem parameter. There
>    have been reports that the initial memory accounting for Xen and
>    Dom0 is bogus for a PVH Dom0 depending on the host amount of RAM
>    and other factors. This will involve testing PVH Dom0 on several
>    boxes without the dom0_mem parameter and coming up with a better
>    algorithm to calculate the amount of memory required by Xen and
>    Dom0. Changes will be mostly limited to the dom0_compute_nr_pages
>    and dom0_paging_pages functions I expect.
- Linux: there are issues in the way Linux maps foreign memory and
>    grants when running in PVH mode. AFAIK Linux will balloon out RAM
>    and use the freed range in order to map foreign memory or grants.
>    This can cause out of memory issues if there are enough mappings,
>    and also decreases the RAM available to Dom0 for no reason.
>    Solving this issue requires an analysis of the problem and drafting
>    a document that describes the solution before implementing it, as
>    it's slightly tricky. This document would be sent to xen-devel for
>    review and opinions.

[0] https://lists.xenproject.org/archives/html/xen-devel/2018-10/msg01580.html

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