Re: [Xen-devel] xen-access performance from DomU

[Bread Cutter <cutter409@xxxxxxxxx>]

By the way, this is with Xen-4.4 (although I had the same issue on
4.3), running Ubuntu 13.10 Saucy with kernel 3.11.0-19-generic.

On Thu, Apr 10, 2014 at 6:42 PM, Bread Cutter <cutter409@xxxxxxxxx> wrote:
> Hello all,
>
> I'm having a performance issue with the xen-access API from DomU.
>
> First of all, I've changed xen/include/xsm/dummy.h so that all
> permissions are allowed. This is temporary and for testing, simply so
> that I could run xen-access from DomU. I've also changed
> tools/tests/xen-access/xen-access.c (patch attached) so that I monitor
> cr3 writes. This was just something that happens consistently enough
> for comparing performance. The actual value of cr3 isn't important for
> my testing.
>
> When I run xenaccess in Dom0, the target HVM domain runs pretty
> smoothly. I can launch programs and Windows feels pretty responsive.
>
> However, when I run the same tool from a PV-DomU, the target domain
> becomes extremely sluggish. Launching a web browser takes a long time,
> for example, and it's essentially unusable.
>
> Can anyone offer any insight, and/or a remedy?
>
> Thank you!

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