On Mon, Dec 28, 2015 at 10:09:52AM +0530, Anshuman Khandual wrote: > On 12/24/2015 04:08 PM, David Gibson wrote: > > On Thu, Dec 24, 2015 at 02:52:53PM +0530, Anshuman Khandual wrote: > >> > On 12/22/2015 10:44 AM, David Gibson wrote: > >>> > > I've discussed with Paul and Ben previously the possibility of > >>> > > extending PAPR to allow changing the size of a running guest's hash > >>> > > page table (HPT). This would allow for much more flexible memory > >>> > > hotplug, since the HPT wouldn't have to be sized in advance for the > >>> > > maximum possible memory size of the guest. > >> > > >> > Does it include reducing the size of HPT as well ? > > It does, but that could fail with H_PTEG_FULL if there's a collision > > between bolted entries in the reduced table. > > So in the case when we request for a reduced size HPT table, as mentioned > in the second implementation method, will we allocate the required smaller > HPT table to shadow the original or we just reduce the original HPT in > size without allocating a new one ?
The current implementation will allocate a new HPT and free the
original one once the transition is complete. It might be possible to
avoid that and reduce the HPT in place, but doing a rollback in case
of collision will be a lot hairier.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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