[Xen-devel] Re: Synchronous scrubbing for alloc_domheap_pages()

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

Cancel that... the real problem was that set_pod_target() was trying
to allocate superpages, but not falling back to 4k pages if that
failed.

 -George

On Wed, Sep 23, 2009 at 3:08 PM, George Dunlap
<George.Dunlap@xxxxxxxxxxxxx> wrote:
> I'm running into an issue where alloc_domheap_pages() fails, even
> though there is free memory, because the memory hasn't been scrubbed
> yet.  The context of this is when ballooning down one VM in order to
> start a second VM: the balloon driver on the first VM has reached its
> target, but creation of the second VM fails because the freed memory
> hasn't been scrubbed yet.
>
> In the situation where there is no memory on the free list, but memory
> on the "to-be-srubbed" list, is there any reason why we don't do
> syncronous scrubbing?
>
> The alternative would be to teach the control tools to look at
> unscrubbed vs free memory, and wait until there was enough to start
> the VM; but that seems a bit more hackish.
>
> I chatted with Tim Deegan about this, and the only issue he could see
> would be making sure that hypercalls which called
> alloc_domheap_pages() yielded reasonably.
>
> Thoughts?
>  -George
>

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