Re: [Xen-devel] [PATCH RFC] x86/ioreq server: Optimize p2m cleaning up code in p2m_finish_type_change().

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 05/04/17 09:59, Yu Zhang wrote:
> Previously, p2m_finish_type_change() is triggered to iterate and
> clean up the p2m table when an ioreq server unmaps from memory type
> HVMMEM_ioreq_server. And the current iteration number is set to 256
> And after these iterations, hypercall pre-emption is checked.
> 
> But it is likely that no p2m change is performed for the just finished
> iterations, which means p2m_finish_type_change() will return quite
> soon. So in such scenario, we can allow the p2m iteration to continue,
> without checking the hypercall pre-emption.

Suppose you have a guest with 128TiB of RAM, and the ioreq_server p2m
entries are at the very end of RAM.  Won't this run for several minutes
before even allowing preemption?

 -George


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