Re: repeating 'd1v0 Over-allocation for domain 1' messages in xen 4.7 Host logs on PVHVM Guest launch

[George Dunlap <george.dunlap@citrix.com>]

On Wed, Jun 29, 2016 at 5:27 PM, PGNet Dev <pgnet.dev@gmail.com> wrote:
> In summary, there's a problem
>
>         An indication of the guest trying to allocate more memory that the
> host admin has allowed.
>
> that's filling logs with 10s of thousands of redundant log entries, with a
> suspicion that it's 'ballooning' issue in the guest
>
>         Perhaps something wrong in the guest's balloon driver.
>
> With no currently known way to identify or troubleshoot the problem, and
> provide info here that could be helpful
>
>         I'm simply not aware of existing output which would help; I can't
>         see any way around instrumenting involved code.
>
> Not particularly ideal.
>
> Since this is the recommended bug-report channel, any next suggestions?
>
> Is there a particular dev involved in the ballooning that can be cc'd,
> perhaps to add some insight?

Thanks for your persistence. :-)

It's likely that this is related to a known problem with the interface
between the balloon driver and the toolstack.  The warning itself is
benign: it simply means that the balloon driver asked Xen for another
page (thinking incorrectly it was a few pages short), and was told
"No" by Xen.

Fixing it properly requires a re-architecting of the interface between
all the different components that use memory (Xen, qemu, the
toolstack, the guest balloon driver, &c). This is on the to-do list,
but since it's quite a complicated problem, and the main side-effect
is mostly just warnings like this it hasn't been a high priority.

If the log space is an issue for you your best bet for now is to turn
down the loglevel so that this warning doesn't show up.

 -George

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