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

[Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>]

On 4/5/2017 11:11 PM, George Dunlap wrote:
> On 05/04/17 16:10, George Dunlap wrote:
> > 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?
> Sorry, this should be GiB.  But I think you get my point. :-)
Yep. I got it.
I'd better reconsider it - my head is quite dizzy now. Maybe together 
with your generic p2m change solution in 4.10. :-)
Thanks
Yu
>   -George

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