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

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

And in fact page scrubbing *is* entirely synchronous in xen-unstable now
(but not in any stable branch, as yet).

 -- Keir

On 23/09/2009 15:40, "George Dunlap" <George.Dunlap@xxxxxxxxxxxxx> wrote:

> 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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