Re: [Qemu-devel] memory: memory_region_transaction_commit() slow

[Peter Crosthwaite]

On Thu, Jun 26, 2014 at 4:58 AM, Paolo Bonzini <address@hidden> wrote:
> Il 25/06/2014 19:53, Etienne Martineau ha scritto:
>
>>
>> It seems to me that there is a scale issue O(n) in
>> memory_region_transaction_commit().
>>
>> Basically the time it takes to rebuild the memory view during device
>> assignment
>> pci_bridge_update_mappings() increase linearly with respect to the number
>> of
>> device already assigned to the guest.
>
>
> That's correct, unfortunately.  It can be fixed, it's not hard but also not
> trivial.
>
> Basically you can detect address spaces whose memory region is an alias of
> an address space's root memory region.  You can then reuse that address
> space's FlatView instead of building another one.
>

Sounds like my shareable address spaces scheme:

http://lists.gnu.org/archive/html/qemu-devel/2014-06/msg00366.html

Its not MR alias aware but shouldn't be too hard to extend. Would this help?

Regards,
Peter

> Paolo
>